JP4140872B2 - Bellows mounting structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mounting structure for a bellows used in a fluid device such as a pump or an accumulator, and more particularly to a technique for improving durability by avoiding stress concentration in the bellows.
[0002]
[Prior art]
For example, in a bellows type pump, a bellows provided in a casing is expanded and contracted in the axial direction, thereby changing the volume of the inside and sucking and discharging fluid. FIG. 5 is a view showing a bellows mounting structure of such a bellows type pump. In FIG. 5, reference numeral 1 denotes a ring-shaped flange attached to a casing (not shown), and one end of a bellows 2 is fixed to the flange 1. The bellows 2 is schematically composed of crests 3a, 3b,... Whose cross section is an inverted U shape, and troughs 4a, 4b,... Provided between the crests 3a, 3b,. It is configured. Moreover, the cylindrical part 5 of the same diameter as trough part 4a, 4b, ... is formed in the one end part of a bellows. The cylindrical portion 5 is fitted into the hole 1a of the flange 1 and is welded to the hole 1a at the edge portion P thereof. Further, the flat left lower abdomen 6 of the peak portion 3 a closest to the flange 1 of the bellows 2 is in contact with the inner surface 1 b of the flange 1. Thereby, the positioning at the time of welding the bellows 2 to the flange 1 is made.
[0003]
By the way, when a high-pressure fluid enters the inside of the bellows 2 and the outside is used in an atmospheric pressure state, the crests 3a,... Are expanded by the internal pressure, and the troughs 4a,. Further, when the bellows 2 is compressed, deformation occurs such that the radii of curvature of the crests 3a,... And the troughs 4a,. Here, since the lower left abdomen 6 of the peak portion 3a closest to the flange 1 is restrained by the flange 1, the displacement of the peak portion 3a is minimized. Therefore, the trough 4a adjacent to this crest 3a is pressed against the crest 3a with the least displacement, so that it receives a larger compressive force than the other troughs 4b in a dynamic state. As described above, the valley portion 3a closest to the flange 1 receives a large dynamic compressive force in addition to the compression by the internal pressure, so that a large stress is generated and the durability of the portion is reduced. According to the study of the present inventors, it has been found that the stress generated in the valley 4a is about 30% larger than that of the other valleys 4b.
[0004]
Therefore, in Japanese Patent Laid-Open No. 10-148258, as shown in FIG. 6, the cylindrical portion 4 of the bellows 2 is stepped and applied to the stepped hole 1 a of the flange 1, thereby positioning the bellows 2. In addition, a bellows mounting structure in which a gap is provided between the flange portion 1 and the lower left abdomen 6 of the mountain portion 3a has been proposed. According to this structure, since the lower left abdominal part 6 of the peak part 3a is not restrained by the flange 1, the trough parts 4a,... Receive uniform deformation, there is no concentration of stress, and there is no problem of durability. There is.
[0005]
[Problems to be solved by the invention]
However, in the bellows mounting structure according to the above proposal, in order to position the bellows, the bellows and the flange have to be stepped, and there is a problem that the processing is complicated and an increase in manufacturing cost is inevitable. .
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a bellows mounting structure capable of preventing stress concentration on the bellows with a simple configuration.
[0006]
[Means for Solving the Problems]
As a result of repeated improvements to the bellows mounting structure, the inventor does not increase the stress of the valley 4a even if the peak 3a closest to the flange 1 is not completely free as shown in FIG. I found out. That is, as a result of the numerical analysis of the stress by the finite element method, even if the base part of the peak part 3a is constrained, the peak part 3a can be displaced. Thereby, the stress of the valley part 4a does not increase, and other valley parts It was found that the stress was almost equal to 4b,.
[0007]
The mounting structure of the bellows of the present invention is based on the above knowledge, and includes a fixing member, and a bellows having one end fixed to a hole provided in the fixing member and capable of expanding and contracting in the axial direction. A cylindrical portion fitted and fixed to the fixing member, and a bellows portion in which peaks and troughs alternately and continuously extend from the end of the cylindrical portion, and the bellows sends and receives the fluid. In the mounting structure of a bellows that is applied to a fluid device and expands and contracts in the axial direction when the fluid device is used to change the internal volume of the fluid device to send and receive the fluid, the fixing member is in the axial direction. with abutting projections on the base of the nearest crest to the fixing member protrudes, the outer peripheral side portions than the convex portions, Ri gap der to open between the crest, the convex portion, the cylindrical portion Side inner taper part, gap side outer taper part, cylinder part side It has an abutment surface formed between the taper part and the outer taper part on the gap side, and the inner taper part on the cylinder part side is separated from the base part closest to the fixing member and is tapered on the cylinder part side. The outer taper portion on the gap side is spaced apart from the base portion closest to the fixing member, and expands in a tapered shape on the gap side, and the contact surface is the base portion of the peak portion closest to the fixing member. It is characterized by being a flat surface abutting on the surface .
[0008]
In the bellows mounting structure configured as described above, the bellows can be positioned by bringing the base portion of the peak portion into contact with the convex portion of the fixing member. Moreover, since it is sufficient to provide the convex portions only on the fixing member, the processing is simple and the manufacturing cost can be reduced. Furthermore, since the part on the outer peripheral side with respect to the convex part is open, the peak part closest to the fixing member can be displaced toward the fixing member when the bellows is compressed. Therefore, the valley portion adjacent to the peak portion is appropriately displaced toward the fixing member, and stress is not concentrated on the valley portion, so that the durability can be improved. However, it is desirable that the gap on the outer peripheral side than the convex portion has a width that does not interfere with the crests displaced during compression.
[0009]
In the bellows, the top of the peak and the bottom of the valley are generally arcuate in cross section. For example, the peak can have an inverted U-shaped cross section and the valley can have a U-shaped cross section. Alternatively, as disclosed in Japanese Patent Application No. 10-132778, the base of the peak is It may have a shape in which the width in the axial direction becomes narrow so as to be constricted. Moreover, a linear abdominal part can be provided between the peak part and the valley part in a sectional view.
[0010]
In the configuration as described above, the base portion of the peak portion closest to the fixing member can also have an arc shape in cross section, and the convex portion in that case is desirably a convex curved surface shape so as to make surface contact with the base portion. . In this way, by forming the convex portion so as not to contact the edge of the base portion, local stress concentration at the base portion can be prevented. Further, for the same purpose, it is desirable that the convex portion is in contact with substantially the entire base portion having a circular arc cross section. Further, it is desirable that a portion of the convex portion on the outer peripheral side with respect to the convex curved portion contacting the base portion has a shape that escapes in the axial direction so as to ensure free displacement of the peak portion. Specifically, the outer peripheral portion of the convex portion can be a tapered portion that becomes wider as the distance from the peak portion increases.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A. Configuration of bellows mounting structure An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view showing a bellows pump to which the bellows mounting structure of the embodiment is applied. In FIG. 1, reference numeral 10 denotes a casing. The casing 10 includes a horizontal cylindrical portion 10a extending in the left-right direction in the drawing, and a vertical cylindrical portion 10b extending in the vertical direction at the center between the horizontal cylindrical portions 10a. A flange (fixing member) 11 is fitted into the opening of the horizontal cylindrical portion 10a, and a lid 12 is attached to the outside thereof. A discharge port 13 and a suction hole 14 are formed in the flange 11 and the lid 12, and check valves 13 a and 14 a are respectively attached to these. One end of the bellows 20 is fixed to the flange 11.
[0012]
FIG. 2 shows details of the bellows 20 and the flange 11. As shown in FIG. 2, a cylindrical tube portion 21 is formed at one end portion of the bellows 20. The cylindrical portion 21 is fitted into the hole 11a of the flange 11, and is welded to the hole 11a at the tip edge 21a. Further, a bellows portion 24 is formed at the other end portion of the bellows 20 in which crest portions 22a,... And trough portions 23a,. The peaks 22a,... Have a reverse U-shaped cross section, and the valleys 23a,. Further, a flat belly portion 25 that is substantially orthogonal to the direction of the axis O of the bellows portion 24 is formed between the peak portions 22a,... And the valley portions 23a,. Further, the diameter of the troughs 23a,... Is the same as the diameter of the cylindrical part 21, and the lower left base 26 of the peak part 3a on the most flange 11 side has a circular arc shape with the same curvature as that of the troughs 23a. ing. Such a bellows 20 can be manufactured by plastic working a stainless steel tube, for example.
[0013]
On the other hand, the flange 11 is formed with a protrusion 11b that protrudes in the direction of the axis O along the peripheral edge of the hole 11a. The convex portion 11 b has a semicircular cross section with the same curvature as the base portion 26, and is in surface contact with the base portion 26. In addition, a gap 11c that opens between the ridges 22a is formed on the outer peripheral side of the convex portion 11b, and the width T of the gap 11c is the displacement of the ridges 22a when the bellows 20 is compressed. Is set larger than.
[0014]
Next, as shown in FIG. 1, the tappet 15 is fixed to the other end portion of the bellows 20 so as to face the vertical cylindrical portion 11 b of the casing 10. Reference numeral 16 in the drawing denotes a bearing that slidably supports the tappet 15. A shaft 17 having an upper end projecting to the outside is rotatably supported by the vertical cylindrical portion 11 b, and a cam 17 a is formed at the lower portion of the shaft 17. The cam 17 a is disposed between the tappets 15 and 15 and is pressed by the tappet 15 by the elastic force of the bellows 20. In the figure, reference numeral 18 denotes a bearing that rotatably supports the shaft 17, and 19 denotes an oil seal of the shaft 17. A high-pressure fluid 30 made of gas, liquid, or a mixture thereof is placed in the inner space of the bellows 20, and lubricating oil 31 is placed between the tappets 15 and 15 and in the outer peripheral side of the bellows 20. Filled and atmospheric pressure.
[0015]
B. Operation of the bellows mounting structure Next , the operation of the bellows mounting structure having the above configuration will be described. When the shaft 17 is rotated by a driving device (not shown), one tappet 15 slides in the same direction by the pressing force of the cam 17 and the other tappet 15 by the elastic force of the bellows 20. For example, if the tappets 15, 15 slide to the left from the state shown in FIG. 1, the left bellows 20 is compressed and the fluid 30 is discharged from the discharge port 13, and the right bellows 20 is caused by its elasticity. The fluid 30 is sucked from the suction hole 14 by extending. Thus, when the cam 17a rotates, the bellows 20 expands and contracts, and the fluid 30 is pumped.
[0016]
Now, when the bellows 20 is compressed, as shown in FIG. 2, each peak part 22a, ... and trough part 23a, ... of the bellows 20 will be displaced to the flange 11 side. In FIG. 2, the symbol X indicates the displacement of the valley 23b. At the same time, the pressure of the fluid 30 acts to expand the peaks 22a,... And compress the valleys 23a,. Therefore, the valleys 23a,... Undergo two compression actions, compression due to displacement and compression due to the pressure of the fluid 30, and a greater stress than the peaks 22a,. Here, the base portion 26 of the peak portion 22a closest to the flange 11 is constrained by the convex portion 11b of the flange 11, but the abdominal portion 25 above the base portion 26 is directed to the flange 11 side with the upper end of the base portion 26 as a fulcrum. It can be displaced to bend. That is, a displacement almost equal to that when the peak portion 22a is not restrained at all occurs. As a result, an appropriate displacement also occurs in the valley portion 23a adjacent to the peak portion 22a, and compressive deformation equivalent to the other valley portions 23b,. Therefore, stress concentration does not occur in the valley portion 23a, and durability is improved.
[0017]
Further, when attaching the bellows 20 to the flange 11, the cylindrical portion 21 may be inserted into the hole 11a of the flange 11 and the base portion 26 may be abutted against the convex portion 11b for positioning and welding. The convex portion 11b serving as a positioning reference can be easily machined by turning the flange 11 with a lathe. Or the convex part 11b can be manufactured separately from a flange, and both can also be integrated by suitable means, such as welding and screwing. Thus, according to the present embodiment, stress concentration does not occur in the valley 23a and the durability is high, as well as the processing for positioning the bellows 20 only needs to be performed on the flange 11. Can be simplified and the manufacturing cost can be reduced.
[0018]
C. Other Embodiments Fig. 3 is a diagram showing another embodiment of the present invention. In this embodiment, the shape of the convex portion 41 of the flange 40 is changed. The convex portion 41 has a curved surface portion 41a having the same curvature as that of the base portion 26 and a quadrilateral cross section, and the curved surface portion 41a. It consists of a tapered portion 41b that expands in a tapered shape from the outer peripheral edge toward the flange 40 side. The tapered portion 41b extends from the boundary between the base portion 26 and the abdominal portion 25 (the end of the arc-shaped portion), and the angle formed with the axis O is 45 degrees. Moreover, the outer peripheral side is open | released rather than the taper part 41b, and the clearance gap T is provided. The gap T is set larger than the displacement amount of the peak portion 22a closest to the flange 40. Note that the configuration other than the convex portion 41 is the same as that of the above-described embodiment, and the same reference numerals are given to those and description thereof is omitted.
[0019]
In the bellows mounting structure having the above-described configuration, the outermost side of the curved surface portion 41a is escaped as the tapered portion 41b, as well as the effects equivalent to those of the above-described embodiment. 22a can be displaced more freely. That is, in the above-described embodiment, since the convex portion 11b has a semicircular cross section, the abdomen 25 is deformed so that the abdomen 25 rides on the outer peripheral portion of the convex portion 11b. It can be deformed with almost no restraint. Therefore, local stress does not act on the abdomen 25, and durability can be further enhanced. Further, since the outer peripheral portion of the convex portion 40 only needs to be tapered, the processing is further simplified.
[0020]
Next, FIG. 4 is a diagram showing still another embodiment of the present invention. In this embodiment, the convex portion 51 of the flange 50 has an inner tapered portion 51a on the inner peripheral side, an outer tapered portion 51b on the outer peripheral side, and an abutment provided between these inner and outer tapered portions 51a and 51b. It is comprised from the surface 51c. The contact surface 51c is a flat surface orthogonal to the axis O, and is in contact with the base portion 26 of the peak portion 22a. Note that it is sufficient that the contact surface 51 c is positioned closer to the base portion 26, and a part or all of the contact surface 51 c may be in contact with the abdomen 25.
[0021]
In this embodiment, since the processing of the convex portion 51 can be performed by two taper processing, the processing is further simplified. In addition, in order to relieve per edge of the convex part 51 when the abdominal part 25 deform | transforms, the contact surface 51c can also be formed in a convex curved surface. Alternatively, the boundary between the contact surface 51c and the inner and outer tapered portions 51a and 51b can be rounded. Moreover, the bellows 20 can also be comprised with a synthetic resin, and the bellows 20 is adhere | attached on the flange by the adhesive agent at the end.
[0022]
【The invention's effect】
As described above, according to the bellows mounting structure of the present invention, it is possible to displace the peak portion on the most fixed member side of the bellows, and therefore, it is possible to give an appropriate displacement to the valley portion adjacent to it. The durability can be enhanced by avoiding stress concentration in the valley. Moreover, the process for positioning at the time of attaching a bellows to a fixing member is simplified, and manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a bellows pump to which a bellows mounting structure according to an embodiment of the present invention is applied.
FIG. 2 is a cross-sectional view showing details of the bellows mounting structure of the embodiment.
FIG. 3 is a cross-sectional view showing details of a bellows mounting structure according to another embodiment of the present invention.
FIG. 4 is a cross-sectional view showing details of a bellows mounting structure according to still another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing details of a conventional bellows mounting structure.
FIG. 6 is a cross-sectional view showing another example of a conventional bellows mounting structure.
[Explanation of symbols]
11 ... Flange (fixing member), 11b ... Projection, 11c ... Gap,
20 ... Bellows, 21 ... Tube part, 22a, ... Mountain part, 23a, ... Valley part,
24 ... bellows, 25 ... abdomen, 26 ... base, O ... axis.

Claims (1)

A fixing member and a bellows having one end fixed to a hole provided in the fixing member and capable of expanding and contracting in an axial direction, the bellows being fitted and fixed to the fixing member; and a bellows portion which peaks and valleys are formed by extending alternately and continuously from the end portion, the bellows, while being applied to a fluid device that performs input fluid delivery, the in use of the fluid device In the mounting structure of the bellows that sends and receives the fluid by changing the internal volume of the fluid device by expanding and contracting in the axial direction,
The fixing member, protrudes the axis direction with abutting projections on the base of the ridges closest to the fixing member, the outer peripheral-side portion than the convex portion, opening a between the ridges gap der that is,
The convex portion is an abutting surface formed between the inner tapered portion on the cylindrical portion side, the outer tapered portion on the gap side, and the inner tapered portion on the cylindrical portion side and the outer tapered portion on the gap side. Have
The inner tapered portion on the cylindrical portion side is spaced apart from the base portion closest to the fixing member, and is expanded in a tapered shape on the cylindrical portion side,
The outer taper portion on the gap side is spaced apart from the base portion closest to the fixing member and expands in a tapered shape on the gap side,
The bellows mounting structure , wherein the abutting surface is a flat surface that abuts on the base portion of the peak portion closest to the fixing member .

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