JPS6365410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve case equipped with a valve seat and an oil passage for a base valve provided at the bottom part of a dual-tube hydraulic shock absorber, and in particular to This is a manufacturing method for the above-mentioned valve case that can produce effects that cannot be obtained by ordinary drawing processing methods.The feature is that a circular blank is punched out from a flat plate material, and this is then assembled into a flanged molding process. Following the drawing process to form the final product into a shape, the base valve case of the final product is divided concentrically on the circumference where sharp edges or perpendicularity are required, and is placed in a split mold that is placed above and below. By compressing the axial dimension l ₁ of the intermediate product in one step to the predetermined dimension l of the final product without changing the diameter dimension of the cylindrical part of the intermediate product in the previous process while restraining the flow of the material,
Forging overlay forming of flat surface for annular valve seat,
At the same time, the lower inner peripheral edge of the cylindrical part is formed at a right angle from the flat surface to the flange part, and then, in a punching process, the central through hole and the outer diameter of the flange part are punched out to a predetermined size and shape. This is a method of manufacturing a base valve case for a shock absorber.

The valve case for the base valve in the dual-tube hydraulic shock absorber to which the present invention is applied is well known to those skilled in the field of shock absorber technology, so the details will be omitted; As shown in FIG. 1, for example, the valve case 20 includes an inner cylinder 2 in which a piston 22 having a desired damping force generating valve 21 is slidably accommodated.
3 and an outer cylinder 25 forming an annular reservoir chamber 24 between the outer wall of the inner cylinder 23 and the lower end of the inner cylinder 23 by the outer wall of the base valve case 20 itself. While tightly fitting and supporting the base valve case 20 , an oil passage 27 leading to the annular reservoir chamber 24 is formed between the base valve case 20 and the lower cap 26 . Leaf valve 2
9 and also supports a retainer 31 placed on the leaf valve 29 under the bias of a spring 30, thereby supporting the inner cylinder 2.
When the piston 22 enters into the inner cylinder 23, a damping force is generated by flowing an amount of oil corresponding to the volume of the piston rod 32 entering into the inner cylinder 23 while bending the inner peripheral edge of the leaf valve 29 downward. The oil is sent to the reservoir chamber 24 through the through hole 33 drilled in the center and the oil passage 27, and conversely, when the piston 22 retreats, the negative pressure generated in the piston lower chamber in the inner cylinder 23 causes the leaf valve 29 and the retainer to flow. 31 is opened against the spring 30 to constitute a base valve in a double-tube hydraulic shock absorber so that oil can be sucked in from the reservoir chamber 24.

Therefore, this type of base valve case must have sufficient strength to support the damping load applied via the leaf valve, large vertical load, etc., and the leaf to generate good damping force. Not only is the annular seat surface for the valve required to have uniform precision such as flatness and concentricity, but also accurate outer diameter dimensions and other dimensions to enable a tight liquid-tight fit with the inner cylinder. This requires extremely complex shapes and processing precision, such as the need to provide through holes and recesses to form oil passages, so it is difficult to create them by cutting or other machining. Not only is it difficult, but mass production is extremely poor and nearly impossible.

Therefore, today, this type of base valve case has the required material strength, can be adapted to any shape, and can be produced with relatively high mass productivity under accurate dimensional control. Based on the conventional wisdom that the sintering method is the most suitable method for producing metal powder, the sintering method, in which iron powder is pressurized and baked in a mold, has been widely adopted. Sintered products are the mainstream.

However, this kind of sintered product is not completely without problems; for example, in the case of this type of sintering method, it is necessary to prepare a large number of molds, and of course, There is a powder compaction process for compressing iron powder in a mold, a sintering process for heating and holding it in a heating furnace at over 1,000 degrees and baking it, and a process for correcting distortion and dimensional accuracy of the sintered product. Not only does it require complex work processes such as dimensional finishing processes in straightening molds and large-scale equipment, but iron-based sintered products are brittle and more susceptible to impact than steel materials, so Great care is required when handling during transportation, etc., and in addition, the cost of the product is high due to the costs of complex work equipment and miscellaneous expenses associated with the work, as well as the recent rise in the cost of raw materials for iron powder. This manufacturing method was accompanied by various inconveniences such as sticking.

In addition, as an alternative to the above-mentioned sintering manufacturing method, there is a method of manufacturing a similar base valve case by press drawing, for example, as disclosed in Patent Application Publication No. 37550 published in 1978 and patent application filed in 1978. This was proposed in Publication No. 37551, etc., but in the case of these manufacturing methods, the drawing technique involves a change in the outer diameter of the cylindrical drawing part in each step, in other words, each drawing step The shape of the intermediate drawing part takes into account the punching and deformation of the material during the drawing process, and in particular, the provision of a relaxation curve part to give the necessary deflection characteristics in consideration of the work hardening of the material that accompanies the drawing process. Since the forming process is performed using a general drawing process, each drawing process that involves a change in the outer diameter involves changes in the plate thickness and work hardening of the material surface. It is best from the point of view that fewer steps are advantageous in terms of product dimensional accuracy, as fewer cracks due to work hardening of the material and changes in plate thickness (unevenness) due to anisotropy, etc. Also, not the method of
Due to the general drawing process, corner arcs corresponding to the "die radius + plate thickness" that are typical of this type of drawn product remain at the corners of the cylindrical part. It is undeniable that this method has some disadvantages, such as not providing sufficient rigidity and low buckling strength, especially against vertical loads.

Therefore, an object of the present invention is to provide a method for manufacturing a base valve case for a shock absorber that can simultaneously eliminate the various drawbacks of conventional sintered or drawn products and their processing methods. Next to the previous process of drawing into a flanged tip shape, the base valve case is divided concentrically on the circumference where a sharp edge or perpendicularity is required and is placed above and below. By restricting the flow of the material in the mold and compressing the axial dimension of _the intermediate product in the previous process to the predetermined dimension of the final product without changing the diameter of the cylindrical part, it is possible to create an annular valve seat. Forging overlay forming of the flat surface and right-angled upright forming of the lower inner peripheral edge of the cylindrical part that continues from the flat surface to the flange part are performed simultaneously, and then punching is performed to finish the center through hole and the outer diameter of the flange part. It is characterized by doing the following.

An embodiment of the present invention will be described below with reference to the process diagram shown in FIG.

The first step of the method according to the present invention is a punching step in which a blank 1 having a predetermined dimension is punched out into a circular shape from a steel plate having a predetermined thickness using a press machine, and the subsequent second step is also a punching step in which a blank 1 having a predetermined size is punched out into a circular shape from a steel plate having a predetermined thickness. An outer peripheral flange having a predetermined axial dimension l1 is formed by a die having a hole diameter corresponding to the diameter dimension _d of the cylindrical part and a punch (both not shown) having an outer diameter corresponding to the inner diameter dimension d _p of the cylindrical part. This is a drawing process in which an intermediate product 2 is formed into a tip-shaped intermediate product 2.

Next, as a third step, in the present invention, as shown _in detail in FIG. A lower punch 5 has a concave inclined surface portion 5b that continues at a predetermined slope from a corner portion 5a to a desired position, and a punch sliding hole 6a that tightly surrounds the lower punch 5 is open, and a flange holding hole is provided on the upper surface. A lower split mold 8 constituted by a lower presser pad 6 provided with an annular protrusion 6b and a guide 7 on the outer periphery of the annular protrusion 6b for suppressing excessive protrusion of the outer periphery of the flange portion is placed in a press machine. The outer periphery of an annular flat surface 3a for a valve seat having a desired width is attached to the lower frame 9, and is also attached to the upper frame 13 of the press machine. An annular flat surface 10a having the same outer diameter as the diameter d _o and located on the outer periphery of the tip and corresponding to the annular flat surface 3a of the molded product 3 and its inner edge to the tip shape of the lower punch 5. Correspondingly, there is a knockout 10 that also serves as an upper punch and has a convex inclined portion 10b that continues at a predetermined slope to a desired position, and a knockout sliding hole 11a that tightly surrounds the knockout 10 and extends from the knockout sliding hole 11a to form a final product 4, which will be described later. Opening portion 11c with hole size corresponding to cylindrical portion diameter size d
An upper split mold 1 constituted by an upper die 11 provided with an annular convex portion 11b for holding a flange.
2, and the intermediate product 2 of the second step is trapped between the upper and lower split molds 12 and 8, and the axial dimension of the cylindrical part is changed at once without changing the diameter dimension of the cylindrical part.
l ₁ is the axial dimension l of the final product 4 described later (however, if the third step is a rough forming process, strictly speaking it is up to the dimension l ₂ of the rough formed product, but even in this case l = l ₂ ).

In this case, in the third step, the axial movable gap δ ₁ (about 2 mm in the embodiment of the present invention) between the upper frame 13 for the upper split mold 12 and the die 11 is pressed down. A strong spring 14 (urethane rubber with a spring constant of 2.5 to 3 tons and a spring constant of about 1200 to 1500 Kg/cm ² in this embodiment)
and a lower position adjusting member 15 for adjusting the protrusion dimension of the punch 5 while leaving a predetermined axial gap δ ₃ between the punch 5 and the pusher pad 6, and between the knockout 10 and the die 11. The upper position adjusting member 16 etc. is used to adjust the protrusion dimension of the knockout 10 by leaving a predetermined axial retraction gap δ ₂ (approximately 5 mm in this example) in the predetermined axial direction of each part of the mold component. Due to the size settings, when the upper and lower split molds 12 and 8 approach each other and reach the bottom dead center, the cylindrical part of the intermediate product 2 is first compressed by the upper split mold 12 and the lower split mold 8, and its own At the same time as the axial dimension l _{1 is crushed from l 1} to l ₂ , the flange portion of the intermediate product 2 begins to protrude toward the guide 7 of the lower split mold 8 , and in response, the flange portion of the intermediate product 2 begins to protrude toward the guide 7 of the upper split mold 12 . Upper and lower flange holding annular convex portions 11b, 6 on the pressure pad 6 of the lower split mold 8
b restrains the bulging flange part under the elastic action of the strong spring 14 one inch before the flange part that has started to bulge out comes into contact with the guide 7, and during the stroke of the movable gap δ ₁ , It continues to be restrained by a frictional pressing force depending on the elastic force of the spring 14. In parallel with this restraining action, forming is gradually performed by the inner punch 5 and the knockout 10, and the fitting boundary between the upper knockout 10 and the die 11 is used for a valve seat that requires a degree of sharpness in the final product. The outer periphery X of the annular flat surface 3a is defined, and the fitting boundary between the lower punch 5 and the pressure pad 6 defines the lower inner periphery Y of the cylindrical portion rising from the outer flange portion where perpendicularity is required in the final product. A sharp edge split mold is constructed by the relationship between the fitting surface and the end surface of each of these members. In the intermediate product 2 located in these split molds, the flow of the material to the outside is restricted due to the frictional resistance restraint effect by the flange holding annular convex portions 11b and 6b at the outer peripheral flange portion. While being confined, the product forming mold itself according to the present invention is gradually formed by the punch 5, pressure pad 6, knockout 10 and die 11 of each divided mold 8, 12 until the press reaches the bottom dead center. Due to the degree of freedom of the mold during this single compression molding and forging process, the material confined within the mold itself is allowed to flow relatively freely, and the intermediate product is The mass of the cylindrical part can be gathered to the outer periphery of the seat, which becomes the annular flat surface for the valve seat, and since it is a one-time compression molding and forging process, there is little work hardening, and no material escapes to the outside. Coupled with the so _- called cold forging build _- up forming action that does not have a A third step molded product 3 having a predetermined shape is molded. In the actual molded product, the one with the expected plate thickness of 1 mm is
Filled with meat to a thickness of 1.5mm.

In other words, in the case of the present invention, the molding die that forms the valve seat portion of the final product 4 is formed only at the bottom dead center of the press by the lower punch 5, the pressure pad 6, and both knockouts 10 and die 11. It becomes.

In addition, in the embodiment of the present invention, if the required corner arc size that determines the degree of sharpening of each part in the final product 4 is very strict (for example, the radius is 0.3 mm or less), the same process as the third step is performed. The compression molding forging process using the split mold may be repeated again as the 3' process. However, since the required corner arc dimensions are usually not very strict, in such cases, the third
Since the step provides the required sharp edge, it is sufficient to perform this step once, and the repeat step (3' step) is completely unnecessary.

In the next fourth step, punching of the central through hole 4a for shaping the final product 4 and punching for cutting the edge 4b of the outer peripheral flange part to the final finished dimensions are performed simultaneously. This is a punching process to obtain . In this case, in the embodiment of the present invention, the inner and outer circumferential parts of the molded product are simultaneously punched, so the required coaxiality (concentricity) can be obtained as the mold precision, which is obvious in terms of product accuracy. advantageous to

Of course, since the above-mentioned hole drilling and ear removal are commonly performed punching processes,
It is also possible to carry out this process separately, and when the number of processing steps is large, but a single transfer machine is used to carry out the process, the mold is simplified and its manufacture becomes easy.

In addition, in the case of the above embodiment as the punched shape of the outer peripheral flange portion, for example, the reservoir chamber 24 and the inner cylinder 23 formed between the inner cylinder 23 and the outer cylinder 25 as illustrated in FIG.
Oil passage 2 for communicating with the lower piston chamber inside
In order to be compatible with the lower cap 26a, which is provided with a plurality of protrusions 34 necessary to form and secure the lower cap 7a, a flange portion is placed on the protrusion 34 of the lower cap 26a, and the flange portion is coaxial with the central axis ( concentricity) and the protrusion 3
Although the case of a simple circumferential flange shape in which lateral movement is reliably restricted by the inclined angle portion 36 rising from the cylindrical wall portion 35 from the cylindrical wall portion 35 is illustrated,
The punched shape of the outer periphery flange can be various shapes as long as the desired oil passage between the inner cylinder and the outer cylinder is secured, for example, as shown in FIG. In order to adapt to the conventional lower cap 26 without a protrusion, a so-called starfish-shaped spacer 37 having a desired thickness is used.
The base valve case 4' may be formed as a base valve case 4' having a plurality of notches 38 on the outer periphery of the flange portion for forming oil passages. The form of can be adopted. Further, as a step after the fourth step, for example, if the molded product is required to have wear resistance, surface treatment such as tuftride treatment may be performed.

As described above, according to the method for manufacturing a base valve case of a shock absorber according to the present invention, the base valve case of the final product is divided concentrically on the circumference requiring a sharp edge or perpendicularity and is arranged vertically. Using a type forming mold, the intermediate product drawn into a flanged cup shape in the previous process is contained, and the diameter of the cylindrical part of the intermediate product is changed while restricting the flow of the material within the same mold. By compressing the axial dimension l ₁ to the predetermined dimension l in the final product in one fell swoop, the forged overlay forming of the flat surface for the annular valve seat and the lower part of the cylindrical part that continues from the flat surface to the flange part are performed. It is characterized by forming the inner peripheral edge at right angles at the same time, and then punching out the center through hole and the outer diameter of the flange part to the specified dimensions and shape in the punching process. There is no change in the diameter of the die, and the outside diameter of the flanged cup-shaped molded product that has been drawn and formed is maintained while being processed.
There is no change in plate thickness or outer diameter dimension that is typical of drawing forming, and the material is processed in a state where there is little work hardening, so the effects of material anisotropy and work hardening are minimized. You can easily obtain products with uniform precision without distortion or cracking.
In addition, the valve seat surface, which is extremely important in setting the damping force characteristics of the shock absorber, can be obtained in a state with no eccentricity with respect to the base valve while ensuring uniform flatness and accurate concentricity. It is possible to reliably and easily obtain an annular flat surface for a valve seat having a uniform width. In addition, the material particles can be compressed and made into fine grains through a single compression molding and forging process, making it possible to make the valve seat surface more flat. Furthermore, the inner peripheral edge of the lower part of the cylindrical part of the cylindrical part supporting the annular flat surface for the valve seat and the outer periphery flange part connected to the cylindrical part has a sharp edge perpendicularity that is so sharp that it cannot be obtained by ordinary drawing processing technology. Because it can be assembled and molded,
High rigidity against vertical loads applied to the base valve case (according to experiments with this example product)
(able to withstand a vertical load of 1.7 tons), for example,
When used in a shock absorber like a conventional draw-formed product with arcs at the corners, there is no bending change in the arcs at the corners due to load fluctuations, and it has sufficient rigidity. Since the base valve can be supported at the bottom, there is no deflection during shock absorber operation, and the damping function and damping force characteristics can be reliably guaranteed, making it highly reliable. It is something that plays.

In addition, according to the present invention, manufacturing of a base valve case for a shock absorber is extremely simple compared to the conventional sintering method, the equipment and processes used are simplified, and it is excellent in mass production, and In addition to eliminating the various drawbacks of the method, the product itself is also lighter than sintered products, and in the case of sintered products, the damping force characteristics of the buffer are improved to eliminate the influence of the roughness of the powder particles. Although finishing of the valve seat surface was required, it is possible to obtain a highly accurate annular flat surface for a valve seat that is completely free from the influence of such particles.

Furthermore, even when carrying out the manufacturing method according to the present invention, although the so-called cold forging process is included in one process, the necessary equipment is used to change the outer diameter following the drawing process in the previous process. It is small because it does not involve
50~80ton (surface pressure 80~130Kg/ ^cm2 approx.) Press machine 1
This can be fully covered by the machine, and the large capacity generally required for cold forging processing (usually
It is advantageous because it does not require mechanical equipment (approximately 160 tons, surface pressure is about 200 to 250 Kg/cm ² ), and because it is a split mold, it can be used even if parts of the mold are subject to severe wear or breakage occurs. Since parts can be replaced without replacing the whole, it is economically advantageous in terms of mold molding and maintenance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional double-tube hydraulic shock absorber using a base valve case manufactured by a sintering method, and FIG. 2 is an embodiment of the base valve case manufacturing method of the present invention. FIG. 3 is an explanatory diagram showing an example of a split forging die used when carrying out the method of the present invention, and FIG.
Figure 5 is a partial cross-sectional view of a case where a base valve case with a shape as shown in the process explanatory diagram is used in a shock absorber. FIG. DESCRIPTION OF SYMBOLS 1...Circular blank, 2...Intermediate product, 4, 4'...Base valve case manufactured according to the present invention, 4a
...through hole, 8...lower split mold, 12...upper split mold, X...sharp edge of annular flat surface for valve seat, Y...lower inner peripheral edge of the cylindrical part rising at right angles from the outer peripheral flange.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a valve case for a base valve in a dual-tube hydraulic shock absorber, comprising: a punching step of punching a circular blank having a predetermined dimension from a flat plate having a predetermined thickness; A drawing process in which a blank is drawn into an intermediate product in the shape of a tip with an outer periphery flange, and a knockout that also serves as an upper punch having an outer diameter that is the same as the outer diameter d _o of the annular flat surface for the valve seat in the final product; an upper split mold consisting of an upper die having an annular convex portion for holding a flange on the lower surface having an opening corresponding to the diameter dimension _d of the cylindrical part of the intermediate product; A lower split mold consisting of a lower punch having an outer diameter and a lower pressure pad having an annular convex portion for holding a flange on the upper surface is arranged concentrically, and the intermediate product is placed in the upper and lower split molds. By simultaneously compressing the axial dimension _l1 to the predetermined dimension l of the final product without changing the diameter of the cylindrical part, the flat annular surface for the valve seat can be forged and overlaid at the same time. A compression molding forging process in which a forged product is formed by vertically forming the lower inner circumferential edge of the cylindrical part that continues from the surface to the flange part, and the center of the bottom of the forged product and the outer diameter of the flange part are set to predetermined dimensions. A method for manufacturing a base valve case for a shock absorber from a flat plate, comprising: a punching step of punching out a through hole and a flange portion. 2. A method according to claim 1 for manufacturing a valve case for a base valve in a dual-tube hydraulic shock absorber, in particular, by repeating the compression molding and forging process using the same mold. A method for manufacturing a base valve case for a shock absorber from a flat plate, characterized by compression molding a forged product. 3. A method according to claim 1 or 2 for manufacturing a valve case for a base valve in a dual-tube hydraulic shock absorber, which particularly includes punching a through hole in the center of the bottom of the forged product. process and
A method for manufacturing a base valve case for a shock absorber from a flat plate, characterized in that one of the steps of punching out the outer diameter of the flange portion into a predetermined size and shape is performed first, and then the remaining steps are performed.