JP2021067280A - Spring and method for manufacturing spring - Google Patents

Abstract

To provide a spring that has excellent dimensional accuracy and non-linear spring property, and to provide a method for manufacturing a spring.SOLUTION: A spring includes: a spring part; and a terminal part provided in both ends of the spring part. The spring part and the terminal part are integrally made with a sintered metal material. The spring part includes: a first spring part having a relatively small cross-sectional area; and a second spring part having a relatively large cross-sectional area.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to springs and methods of manufacturing springs.

Patent Document 1 discloses a spring configured by arranging a plurality of coil spring elements having different spring constants in series. An example of this spring is a single unequal pitch coil spring formed by continuously winding a single spring steel wire having a uniform wire diameter and changing the pitch stepwise in the middle. This coil spring has a non-linear characteristic in which the spring constant increases stepwise.

JP-A-11-107503

Generally, a coil spring is formed by winding a single spring steel wire. Therefore, the conventional coil spring is liable to be distorted due to bending. Further, the spring formed by the bending process tends to have variations in dimensional accuracy. In a coil spring, if machining strain is introduced or the dimensional accuracy varies, it is difficult to obtain stable spring characteristics.

Further, when manufacturing an unequal pitch coil spring from a single spring steel wire, it is necessary to change the pitch stepwise during winding. If the pitch is changed during winding, the variation in dimensional accuracy tends to increase. Therefore, it is difficult to obtain a spring having a predetermined non-linear characteristic.

One object of the present disclosure is to provide a spring having high dimensional accuracy and non-linear spring characteristics. Another object of the present disclosure is to provide a method for manufacturing a spring, which can suppress variations in dimensional accuracy and obtain stable spring characteristics.

The spring of the present disclosure is
A spring portion and terminal portions provided at both ends of the spring portion are provided.
The spring portion and the terminal portion are integrally formed of a sintered metal material.
The spring portion includes a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.

The method for manufacturing a spring of the present disclosure is described.
A process of forming a powder compact by pressurizing and compressing a raw material powder containing a metal powder,
The process of cutting the powder compact to form a spring shape,
The step of sintering the powder compact processed into the shape of a spring is provided.
The shape of the spring is
It integrally has a spring portion and terminal portions provided at both ends of the spring portion.
The spring portion has a shape including a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.

The springs of the present disclosure have high dimensional accuracy and non-linear spring characteristics. The spring manufacturing method of the present disclosure can suppress variations in dimensional accuracy and obtain stable spring characteristics.

FIG. 1 is a schematic side view showing the appearance of the spring according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the spring according to the first embodiment cut by a plane including the central axis of the coil portion. FIG. 3 is a schematic perspective view showing the appearance of the powder compact used for manufacturing the spring according to the first embodiment. FIG. 4 is a schematic side view showing the appearance of the spring according to the second embodiment. FIG. 5 is a schematic cross-sectional view of the spring according to the second embodiment cut by a plane including the central axis of the coil portion. FIG. 6 is a schematic side view showing the appearance of the spring according to the third embodiment. FIG. 7 is a schematic cross-sectional view of the spring according to the third embodiment cut by a plane including the central axis of the coil portion. FIG. 8 is a schematic side view showing the appearance of the spring according to the fourth embodiment. FIG. 9 is a schematic perspective view showing the appearance of the powder compact used for manufacturing the spring according to the fourth embodiment. FIG. 10 is a schematic side view showing the appearance of the spring according to the fourth embodiment. FIG. 11 is a schematic perspective view showing the appearance of the powder compact used for manufacturing the spring according to the fourth embodiment. FIG. 12 is a schematic side view showing the appearance of the spring according to the fifth embodiment. FIG. 13A is a schematic cross-sectional end view taken along the line AA of FIG. FIG. 13B is a schematic cross-sectional end view taken along the line BB of FIG. FIG. 13C is a schematic cross-sectional end view taken along the line CC of FIG.

[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.

(1) The spring according to the embodiment of the present disclosure is
A spring portion and terminal portions provided at both ends of the spring portion are provided.
The spring portion and the terminal portion are integrally formed of a sintered metal material.
The spring portion includes a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.

The spring of the present disclosure is made of a sintered metal material. The sintered metal material is a material obtained by molding and sintering metal powder. As will be described later, the spring of the present disclosure is manufactured by cutting a dust compact before sintering, which is a material for a sintered metal material, and then sintering the compact. Since the spring of the present disclosure is processed into the shape of a spring by cutting, the variation in dimensional accuracy is small as compared with a conventional spring formed by winding a spring steel wire. Further, if the shape of the spring is processed by cutting, the degree of freedom in selecting the shape and size of each of the first spring portion and the second spring portion is high. Therefore, the spring of the present disclosure has high dimensional accuracy, and it is easy to obtain predetermined spring characteristics.

Further, the spring portion provided in the spring of the present disclosure includes a first spring portion and a second spring portion. The first spring portion and the second spring portion have different cross-sectional areas. That is, the spring portion has a portion having a different cross-sectional area. Since the first spring portion has a relatively small cross-sectional area, the amount of deformation with respect to the load is large. On the other hand, since the second spring portion has a relatively large cross-sectional area, the amount of deformation with respect to the load is small. That is, the first spring portion has a relatively small spring constant, and the second spring portion has a relatively large spring constant. Therefore, when a load is applied to the spring portion, the deformation of the spring portion becomes non-linear with respect to the load. Therefore, the springs of the present disclosure have non-linear spring properties. Hereinafter, the "non-linear spring characteristic" may be referred to as a "non-linear characteristic". The cross-sectional area of the spring portion refers to the area of the cross section orthogonal to the length direction of the spring portion.

(2) As a form of the spring of the present disclosure,
The spring portion may be composed of at least one coil portion formed in a spiral shape.

In the above form, since the coil portion constituting the spring portion is formed in a spiral shape, it can be elastically deformed with respect to a load. The coil portion is formed by, for example, forming a spiral groove by cutting from the inner circumference or the outer circumference of the cylinder on a cylindrical dust compact. Hereinafter, the spring of the above-described form in which the spring portion is composed of the coil portion is referred to as a “coil-shaped spring”.

(3) As a form of the coiled spring,
In the cross section including the central axis of the coil portion, the vertical thickness of the second spring portion along the central axis may be larger than the vertical thickness of the first spring portion. ..

In the above embodiment, the cross-sectional area of the second spring portion can be set to be relatively large because the thickness of the second spring portion is larger than the thickness of the first spring portion in the cross section of the coil portion.

(4) As one form of the coiled spring of (3) above,
In the cross section including the central axis of the coil portion, the width of the first spring portion and the second spring portion in the lateral direction orthogonal to the central axis may be constant.

In the above form, the coiled spring can be efficiently manufactured. The reason for this is that if the widths of the first spring portion and the second spring portion are constant, for example, a spiral groove is machined by cutting into a cylindrical dust compact to form a coil portion. This is because the groove is machined to a certain depth. If the groove is processed to a certain depth, the processing is easy.

(5) As one form of the coiled springs (2) and (3) above,
In the cross section including the central axis of the coil portion, the lateral width of the second spring portion orthogonal to the central axis may be larger than the lateral length of the first spring portion.

In the above embodiment, the width of the second spring portion is larger than the width of the first spring portion in the cross section of the coil portion, so that the cross-sectional area of the second spring portion can be set to be relatively large. Further, when the thickness and width of the second spring portion are increased, the cross-sectional area of the second spring portion can be increased, so that the degree of freedom in designing the spring characteristics is increased.

(6) As a form of the coiled spring,
The spring portion has a plurality of the coil portions, and the spring portion has a plurality of the coil portions.
It can be mentioned that the plurality of coil portions are provided so as not to intersect with each other.

In the above embodiment, more complicated spring characteristics can be obtained by providing the plurality of coil portions so as not to intersect each other. Further, by having a plurality of coil portions, even if one coil portion is damaged, the remaining coil portions function as spring portions. Therefore, according to the above embodiment, it is possible to prevent one coil portion from being damaged and immediately becoming unusable.

(7) As a form of the spring of the present disclosure,
The spring portion may be composed of at least one pillar portion that is curved in a curved shape.

In the above form, since the pillar portion constituting the spring portion is curved in a curved shape, it can be elastically deformed with respect to a load. The pillar portion is formed by, for example, removing a part of a cylindrical dust compact from the inner circumference or the outer circumference of the cylinder by cutting. Hereinafter, the spring of the above-described form in which the spring portion is composed of a pillar portion is referred to as a “columnar spring”.

(8) As one form of the columnar spring,
The spring portion has a plurality of the pillar portions, and the spring portion has a plurality of the pillar portions.
It can be mentioned that the plurality of pillars are provided so as not to intersect each other.

In the above embodiment, more complicated spring characteristics can be obtained by providing the plurality of pillars so as not to intersect each other. Further, by having a plurality of pillars, even if one pillar is damaged, the remaining pillars function as springs. Therefore, according to the above-described embodiment, it is possible to prevent one pillar portion from being damaged and immediately becoming unusable.

(9) As a form of the spring of the present disclosure,
Examples thereof include a form in which the connecting portion between the spring portion and the terminal portion has a curved surface.

In the above embodiment, since the connecting portion between the spring portion and the terminal portion has a curved surface, stress concentration at the connecting portion can be relaxed. Therefore, the above-mentioned form can improve the fatigue strength of the spring.

(10) As a form of the spring of the present disclosure,
The relative density of the sintered metal material is 93% or more and 99.9% or less.

The sintered metal material has a relative density of 93% or more and is dense. Since the sintered metal material has few pores, the pores are unlikely to be the starting point of cracking. Therefore, the spring of the above form has high strength.

(11) As a form of the spring of the present disclosure,
The sintered metal material has a matrix made of an iron-based alloy and has a matrix.
The iron-based alloy may contain one or more elements selected from the group consisting of Cu, Cr, Ni, Mo, Mn, P, Si, B and C.

Iron-based alloys containing the elements listed above, such as steel, which is an iron-based alloy containing C, are excellent in strength. Therefore, the spring of the above form has excellent strength.

(12) As a form of the spring of the present disclosure,
The sintered metal material may have a matrix made of pure titanium or a titanium-based alloy.

Pure titanium or titanium-based alloy has excellent specific strength. In particular, the titanium-based alloy has a high specific strength. Therefore, the spring of the above form is lightweight and has excellent strength.

(13) The method for manufacturing a spring of the present disclosure is as follows.
A process of forming a powder compact by pressurizing and compressing a raw material powder containing a metal powder,
The process of cutting the powder compact to form a spring shape,
The step of sintering the powder compact processed into the shape of a spring is provided.
The shape of the spring is
It integrally has a spring portion and terminal portions provided at both ends of the spring portion.
The spring portion has a shape including a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.

The spring manufacturing method of the present disclosure can manufacture a spring made of a sintered metal material. In the method for manufacturing a spring of the present disclosure, since the powder compact is processed into the shape of a spring by cutting, the spring can be manufactured with high productivity. In the manufacturing method of the present disclosure, since the shape of the spring is processed by cutting, variations in dimensional accuracy can be suppressed. Therefore, according to the manufacturing method of the present disclosure, stable spring characteristics can be obtained. Further, since the powder compact before sintering is a molded metal powder, it is easier to cut than the sintered metal material after sintering. Therefore, the manufacturing method of the present disclosure requires a short machining time and extends the life of the machining tool as compared with the case of machining a sintered metal material. Further, since the cutting process can be easily performed, it is easy to obtain a spring having excellent dimensional accuracy. Therefore, according to the manufacturing method of the present disclosure, a spring having high dimensional accuracy can be obtained, so that the yield can be increased.

Further, in the method for manufacturing a spring of the present disclosure, the shape of the spring is a shape in which the spring portion includes a first spring portion and a second spring portion. The first spring portion and the second spring portion have different cross-sectional areas. That is, the spring portion has a portion having a different cross-sectional area. Therefore, according to the manufacturing method of the present disclosure, a spring having a non-linear characteristic can be obtained. Specific examples of the shape of the spring include the shape of the coiled spring in which the spring portion is formed in a spiral shape, and the shape of the columnar spring formed in which the spring portion is curved in a curved shape.

[Details of Embodiments of the present disclosure]
Hereinafter, specific examples of the spring according to the embodiment of the present disclosure and the method for manufacturing the spring will be described with reference to the drawings as appropriate. The same reference numerals in the figures indicate the same names. It should be noted that the present invention is not limited to these examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

[Embodiment 1]
(Overview of spring)
The spring 1 of the first embodiment will be described mainly with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the spring 1 of the first embodiment includes a spring portion 10 and terminal portions 21 and 22 provided at both ends of the spring portion 10. The spring portion 10 includes a first spring portion 11 having a relatively small cross-sectional area and a second spring portion 12 having a relatively large cross-sectional area. One of the features of the spring 1 is that the spring portion 10 and the terminal portions 21 and 22 are integrally formed of a sintered metal material. Here, in the spring 1, one terminal portion 21 side is on the upper side and the other terminal portion 22 side is on the lower side.

In the first embodiment, an embodiment in which the spring portion 10 is composed of one coil portion 10a formed in a spiral shape is illustrated. That is, the spring 1 of the first embodiment is a so-called coiled spring. The appearance of the spring 1 is cylindrical. Hereinafter, the configuration of the spring 1 will be described in detail.

(Spring part)
The spring portion 10 is a portion that acts as a spring. In this example, since the coil portion 10a constituting the spring portion 10 is formed in a spiral shape, it can be elastically deformed with respect to a load. The spring portion 10 has a first spring portion 11 and a second spring portion 12. As shown in FIG. 2, the first spring portion 11 has a relatively small cross-sectional area, and the second spring portion 12 has a relatively large cross-sectional area. That is, the cross-sectional area of the second spring portion 12 is larger than the cross-sectional area of the first spring portion 11. When a load is applied to the spring portion 10 in the vertical direction, the first spring portion 11 having a small cross-sectional area has a large amount of deformation with respect to the load, and the second spring portion 12 having a large cross-sectional area has a large amount of deformation with respect to the load. It becomes smaller. Therefore, when a load is applied to the spring portion 10, the deformation of the spring portion 10 becomes non-linear with respect to the load. Therefore, the spring 1 has a non-linear spring characteristic. The cross-sectional area of each of the spring portions 11 and 12 is the area of the cross section orthogonal to the length direction of the spring portions 11 and 12. When the spring portion 10 is composed of the coil portion 10a as in this example, the cross section is a cross section cut by a plane including the central axis of the coil portion 10a.

The spring portion 10 is formed by cutting a tubular dust compact as described later. The cross-sectional shape of the spring portion 10 can be appropriately selected. In this example, as shown in FIG. 2, the cross-sectional shape of the spring portion 10 is quadrangular. If the cross section of the spring portion 10 is quadrangular, the spring portion 10 can be easily cut. Further, the cross-sectional area of the spring portion 10 of this example changes stepwise from one terminal portion 21 side to the other terminal portion 22 side. More specifically, the cross-sectional area changes continuously only at the transition portion between the first spring portion 11 and the second spring portion 12. The spring portion 10 can also continuously change the cross-sectional area from one terminal portion 21 side toward the other terminal portion 22 side.

In this example, as shown in FIG. 2, in the cross section of the coil portion 10a, the vertical thickness t _{12 of} the second spring portion 12 is larger than the _{vertical thickness t 11 of} the first spring portion 11. large. In the case of this example, the thicknesses t ₁₁ and t ₁₂ of the spring portions 11 and 12 are the lengths in the direction along the central axis of the coil portion 10a, that is, in the vertical direction. Since the thickness t _{12 of the second spring portion 12 is larger than the thickness t 11} of the first spring portion 11, the cross-sectional area of the second spring portion 12 is set to be relatively large. _{The thicknesses t 11} and t ₁₂ of the spring portions 11 and 12 may be appropriately set so as to have a cross-sectional area in which a predetermined spring characteristic can be obtained.

In this example, in the cross section of the coil portion 10a, the lateral widths w ₁₁ and w _{12 of the spring portions 11 and 12} are constant. That is, the above-mentioned width w ₁₁ of the first spring portion 11 and the width w ₁₂ of the second spring portion 12 are substantially equal. In this example, the width _{w 11, w 12} of each spring 11, 12 the direction perpendicular to the central axis of the coil portion 10a, is that words in the radial direction of the length. The coil portion 10a of this example is formed by a cylindrical spiral. The inner and outer diameters of the coil portion 10a are constant over the entire length of the coil portion 10a. That is, the inner and outer diameters of the spring portions 11 and 12 are substantially the same.

In this example, the shape of the coil portion 10a is cylindrical, but the shape is not limited to this. The shape of the coil portion 10a may be, for example, a square tubular shape, a hollow truncated cone shape, a hollow truncated cone shape, or the like.

In addition, in this example, the pitch of the spiral in the coil portion 10a is uniform over the entire length of the coil portion 10a. That is, the pitches of the spirals in the spring portions 11 and 12 are substantially equal. That is, the coil portions 10a have equal pitches. The pitch of the spiral is the distance between the centers of the turns adjacent to each other in the vertical direction in the cross section including the central axis of the coil portion 10a. In other words, the pitch of the spiral is the distance between the centers of the above-mentioned thicknesses of the spring portions 11 and 12. In the case of this example, as described above, since the thickness t _{12 of the second spring portion 12 is larger than the thickness t 11 of} the first spring portion 11, there is an interval between adjacent turns in the second spring portion 12. The gap is narrower than the gap between adjacent turns in the first spring portion 11. The pitch of the spiral is not particularly limited, and may be appropriately set so as to obtain a predetermined spring characteristic. The pitch of the spiral in each of the spring portions 11 and 12 may be different. That is, the coil portions 10a may have unequal pitches. For example, the pitch of the spiral in the first spring portion 11 is smaller than the pitch of the spiral in the second spring portion 12. Specifically, the first spring portion 11 and the second spring portion 12 are set so that the sizes of the gaps between the adjacent turns are equal. The spring characteristics can be controlled by changing the pitch of the spiral.

Further, the number of spiral turns in the coil portion 10a is not particularly limited, and may be appropriately set so as to obtain a predetermined spring characteristic. The number of spiral turns in each of the spring portions 11 and 12 may be the same or different.

(Terminal part)
The terminal portions 21 and 22 are portions that do not act as springs. As shown in FIG. 1, the terminal portions 21 and 22 are integrally formed at both ends of the coil portion 10a. The terminal units 21 and 22 come into contact with a mating member (not shown). The terminal portions 21 and 22 may be provided with attachment portions (not shown) for attaching the spring 1 to the mating member. The mounting portion may be formed of, for example, holes, grooves, protrusions, or the like.

The shapes of the terminals 21 and 22 can be arbitrarily selected. It is preferable that the end faces of the terminal portions 21 and 22 are planes orthogonal to the vertical direction of the spring 1, that is, the axial direction. In this case, there is no step on the end faces of the terminal portions 21 and 22, and the end faces of the terminal portions 21 and 22 can be brought into surface contact with the seating surface of the mating member. In addition, the terminal portions 21 and 22 may have a shape that also serves as a part or all of the mating member. As a result, there is no interface between the spring 1 and the mating member, and both can be handled as one member, which contributes to the reduction of the number of parts.

In this example, the terminals 21 and 22 have a cylindrical shape. The shapes of the terminal portions 21 and 22 are not limited to the cylindrical shape, and can be changed as appropriate. The shapes of the terminal portions 21 and 22 may be, for example, a prismatic shape, a columnar shape, a prismatic shape, or the like. The inner and outer diameters of the terminal portions 21 and 22 of this example are the same as the inner and outer diameters of the coil portion 10a.

(Connection part)
As shown in FIG. 1, connecting portions 31 and 32 are provided between the spring portion 10 and the terminal portions 21 and 22. In this example, the connecting portions 31 and 32 have a curved surface. Therefore, the stress concentration at the connecting portions 31 and 32 can be relaxed, so that the fatigue strength of the spring 1 is improved.

(Sintered metal material)
The spring 1 is made of a sintered metal material. The sintered metal material is a sintered material mainly composed of metal. The sintered metal material includes a matrix made of metal and a plurality of pores existing in the matrix. Since the sintered metal material has pores, it can be impregnated with, for example, lubricating oil. Hereinafter, preferred embodiments of the sintered metal material will be described.

(composition)
Examples of the metal constituting the matrix include various pure metals or alloys. Examples of the pure metal include Fe (iron), Ti (titanium), Cu (copper), Al (aluminum), Mg (magnesium), Ni (nickel), W (tungsten), Mo (molybdenum) and the like. Examples of the alloy include iron-based alloys, titanium-based alloys, copper-based alloys, aluminum-based alloys, magnesium-based alloys, nickel-based alloys, tungsten-based alloys, molybdenum-based alloys, and the like. Among these, iron-based alloys are excellent in strength. Pure titanium or titanium-based alloy is excellent in strength, corrosion resistance, and heat resistance. Therefore, the sintered metal material whose parent phase is an iron-based alloy has high strength. A sintered metal material whose parent phase is pure titanium or a titanium-based alloy has high strength, and also has high corrosion resistance and heat resistance. Since pure aluminum or an aluminum-based alloy, pure magnesium or a magnesium alloy has a small specific gravity, a sintered metal material having a matrix of these metals is lightweight. A sintered metal material whose parent phase is pure nickel or a nickel-based alloy has excellent heat resistance and corrosion resistance. Since tungsten-based alloys and molybdenum-based alloys have a high melting point and are excellent in heat resistance, sintered metal materials having a matrix of these metals are excellent in heat resistance. The higher the strength of the sintered metal material, the more excellent the strength of the spring 1 can be obtained. Among them, pure titanium or titanium-based alloy is excellent in specific strength. In particular, the titanium-based alloy has a high specific strength. Therefore, when the matrix is made of pure titanium or a titanium-based alloy, the spring 1 which is lightweight, has high strength, and has excellent corrosion resistance and heat resistance can be obtained. When the matrix is made of pure aluminum or an aluminum base alloy, pure magnesium or a magnesium alloy, a lightweight spring 1 is obtained. When the matrix is made of pure nickel or a nickel-based alloy, a tungsten-based alloy, or a molybdenum-based alloy, a spring 1 having excellent heat resistance can be obtained.

The iron-based alloy contains additive elements, and the balance consists of Fe and impurities. The iron-based alloy contains the largest amount of Fe. Additive elements are, for example, from Cu (copper), Cr (chromium), Ni (nickel), Mo (molybdenum), Mn (manganese), P (phosphorus), Si (silicon), B (boron) and C (carbon). One or more elements selected from the group of In particular, it is preferable that the additive element contains one or more elements selected from the group consisting of C, Ni, Mo, and B. It is preferable that two or more kinds of additive elements are contained, and three or more kinds may be contained. Iron-based alloys containing the elements listed above in addition to Fe, such as steel, have high strength.

An iron-based alloy containing C, typically carbon steel, has excellent strength. The content of C is, for example, 0.1% by mass or more and 2.0% by mass or less. The content of C may be 0.1% by mass or more and 1.5% by mass or less, further 0.1% by mass or more and 1.0% by mass or less, and 0.3% by mass or more and 0.9% by mass or less. The content of each element is a mass ratio with the iron-based alloy as 100% by mass.

Ni contributes not only to the improvement of strength but also to the improvement of toughness. The content of Ni is, for example, 0% by mass or more and 8.0% by mass or less. The content of Ni may be 0.1% by mass or more and 5.0% by mass or less, and further 0.5% by mass or more and 4.0% by mass or less. The upper limit may be 3.5% by mass or less, and further may be 2.5% by mass or less.

Mo and B contribute to the improvement of strength.
Mo enhances hardenability. Examples of the Mo content include 0% by mass or more and 2.0% by mass or less, and further 0.1% by mass or more and 2.0% by mass or less. The upper limit may be 1.5% by mass or less.
B enhances sinterability. The content of B includes, for example, 0% by mass or more and 0.1% by mass or less, and further 0.001% by mass or more and 0.003% by mass or less.

Cu, Cr, Mn, P, and Si have the effect of increasing strength and hardenability. The content of each of these elements is, for example, 0.1% by mass or more and 5.0% by mass or less.

The overall composition of the sintered metal material can be analyzed by, for example, energy dispersive X-ray analysis (EDX or EDS), high frequency inductively coupled plasma emission spectrometry (ICP-OES), or the like.

(Relative density)
The relative density of the sintered metal material is 93% or more and 99.9% or less. That is, the sintered metal material contains pores in the range of 0.1% or more and 7% or less. If the ratio of pores is in the above range, it can be said that there are few pores and the pores are dense. Since such a sintered metal material has few pores, the pores are unlikely to be the starting point of cracking. Therefore, when the relative density of the sintered metal material is 93% or more, the spring 1 having high strength can be obtained.

From the viewpoint of strength, the relative density of the sintered metal material is preferably 94% or more, more preferably 96% or more, and particularly preferably 96.5% or more. When the relative density is 94% or more, the pores are less likely to become the starting point of cracking because the pores are smaller. The relative density may be 97% or more, 98% or more.

When the relative density of the sintered metal material is 99.9% or less, particularly 99.5% or less, the productivity can be improved. For example, in the step of molding a dust compact as a material for a sintered metal material, if the molding pressure is increased to increase the relative density of the dust compact, the relative density of the sintered metal is increased. However, if the molding pressure is too high, it is difficult to take out the powder compact from the mold, and the life of the mold tends to be shortened. That is, if the molding pressure becomes excessive, the productivity may decrease. From the viewpoint of productivity, the relative density may be 99% or less.

From the viewpoint of spring strength and productivity, the relative density of the sintered metal material is, for example, 94% or more and 99.5% or less, and further 94% or more and 99% or less.

The relative density (%) of the sintered metal material can be obtained as follows. Take multiple cross sections from sintered metal material. Each cross section is observed with a microscope such as a scanning electron microscope (SEM) or an optical microscope. It is preferable to take a plurality of observation fields from each cross section. The observation field of view is, for example, 10 or more. The size (area) of the observation field of view is, for example, 500 μm × 600 μm = 300,000 μm ² . Image processing is performed on the observation image of each observation field of view to extract a region made of metal. The image processing includes, for example, binarization processing. Find the area of the area made of metal. Furthermore, the ratio of the area of the region made of metal to the area of the observation field of view is obtained. The ratio of this area is regarded as the relative density. The relative densities obtained from multiple observation fields are averaged. This average value is taken as the relative density of the sintered metal material. Extraction of the above-mentioned region made of metal, measurement of the area of the above-mentioned region, and the like may be performed using a commercially available image analysis system, commercially available image analysis software, or the like.

(Organization)
The sintered metal material contains a plurality of pores in any cross section. Each pore is preferably small. If each pore is small, each pore is unlikely to be the starting point of cracking, so that the strength of the spring can be increased. Examples of the index showing the size of the pores contained in the sintered metal material include the perimeter of the pores, the cross-sectional area, and the maximum diameter.

The size of the pores can be determined as follows. An arbitrary cross section of the sintered metal material is observed by SEM, and at least one observation field of view is taken from the above cross section. The size of the observation field of view may be adjusted so that there are 50 or more pores in one field of view. Image processing is performed on the observation image in the observation field of view, pores are extracted, and the size of the pores is measured. Examples of the size of the pores to be measured include perimeter, cross-sectional area, maximum diameter, and the like.

《Perimeter of pores》
The sintered metal material preferably has an average peripheral length of pores of 100 μm or less. The average peripheral length of the pores here is an arbitrary cross section taken from the sintered metal material, and in this cross section, the contour length of each pore is obtained for a plurality of pores, and the average length of each contour is used. is there.

If the average peripheral length of the pores is 100 μm or less, it can be said that most of the pores are pores having a short peripheral length. Pore with a short circumference has a small cross-sectional area. It can be said that the shorter the average peripheral length of the pores, the smaller the cross-sectional area of each pore. If each pore is small, it is unlikely to be the starting point of cracking. Therefore, a sintered metal material having an average pore length of 100 μm or less can further increase the strength of the spring. From the viewpoint of strength, the average peripheral length is preferably 90 μm or less, more preferably 80 μm or less, and particularly preferably 70 μm or less.

The average perimeter of the pores tends to decrease as the relative density of the sintered metal material increases. From the viewpoint of preventing the molding pressure from becoming excessive and improving the productivity as described above, the average peripheral length may be, for example, 10 μm or more, and further 15 μm or more.

<< Cross-sectional area of pores >>
The sintered metal material preferably has an average pore cross-sectional area of 500 μm ² or less. The average cross-sectional area of the pores here is a value obtained by taking an arbitrary cross section from the sintered metal material, obtaining the cross-sectional area of each pore for a plurality of pores in this cross section, and averaging the cross-sectional areas of each.

If the average cross-sectional area of the pores is 500 μm ² or less, it can be said that most of the pores are pores having a small cross-sectional area. It can be said that the smaller the average cross-sectional area of the pores, the smaller the cross-sectional area of each pore. If each pore is small, it is unlikely to be the starting point of cracking. Therefore, a sintered metal material having an average pore cross-sectional area of 500 μm ² or less can further increase the strength of the spring. From the viewpoint of strength, the average cross-sectional area is 480 .mu.m ² or less, further 450 [mu] m ² or less, particularly 430 m ² or less.

The average cross-sectional area of the pores tends to decrease as the relative density of the sintered metal material increases. From the viewpoint of preventing the molding pressure from becoming excessive and improving the productivity as described above, the average cross-sectional area may be, for example, 20 μm ² or more, and further 30 μm ² or more.

The sintered metal material preferably has an average peripheral length of pores of 100 μm or less and an average cross-sectional area of pores of 500 μm ² or less. In this case, it can be said that most of the pores are pores having a small cross-sectional area and a short peripheral length. Therefore, each pore is unlikely to be the starting point of cracking. As described above, from the viewpoint of strength, the smaller the average peripheral length and the average cross-sectional area are, the more preferable.

《Maximum diameter of pores》
Further, it is preferable that the average value of the maximum diameters of the pores is also small. The average value of the maximum diameters of the pores here is an arbitrary cross section taken from the sintered metal material, the maximum length of each pore is obtained for a plurality of pores in this cross section, and the average value of each maximum length is used. is there.

The average value of the maximum diameters of the pores is, for example, 5 μm or more and 30 μm or less. If the average value is 30 μm or less, it can be said that most of the pores are short and small. Such pores are less likely to be the starting point of cracking. Therefore, the sintered metal material in which the average value of the maximum diameters of the pores satisfies 30 μm or less can further increase the strength of the spring. From the viewpoint of strength, the average value is preferably 28 μm or less, more preferably 25 μm or less, and particularly preferably 20 μm or less. If the average value is 5 μm or more, the pores are not too small. From the viewpoint of preventing the molding pressure from becoming excessive and improving the productivity as described above, the average value may be 8 μm or more, and further 10 μm or more. From the viewpoint of strength and productivity, the average value is, for example, 10 μm or more and 25 μm or less.

Further, it is preferable that the maximum value of the maximum diameter of the pores is also small. This is because each pore is unlikely to be the starting point of cracking. The maximum value is, for example, 30 μm or less, more preferably 28 μm or less, and particularly preferably 25 μm or less.

The minimum value of the maximum diameter of the pores is, for example, 3 μm or more and 20 μm or less, and further 5 μm or more and 18 μm or less. When the minimum value is in the above range, it is preferable in terms of productivity as described above.

《Shape of pores》
In the cross section of the sintered metal material, the shape of the pores is typically a different shape. One of the reasons why the shape of the pores is not a simple curved shape such as a circle or an ellipse but a deformed shape is that a dense powder compact is sintered at a relatively low temperature, as will be described later. ..

(Spring manufacturing method)
The spring 1 of the first embodiment can be manufactured, for example, by a method for manufacturing a spring including the following steps.
First step: A step of forming a powder compact by pressurizing and compressing a raw material powder containing a metal powder.
Second step: A step of cutting a powder compact to form a spring shape.
Third step: A step of sintering a powder compact processed into a spring shape.

The above-mentioned spring manufacturing method includes the first to third steps, so that a spring made of a sintered metal material can be manufactured. In the above-mentioned manufacturing method, as shown in FIGS. 1 and 2, the shape of the spring integrally includes the spring portion 10 and the terminal portions 21 and 22 provided at both ends of the spring portion 10. The spring portion 10 has a shape including a first spring portion 11 having a relatively small cross-sectional area and a second spring portion 12 having a relatively large cross-sectional area. In the first embodiment, as described above, the spring portion 10 is formed by a coil portion 10a formed in a spiral shape, that is, a so-called coiled spring shape.
Hereinafter, each step will be described.

(First process: molding process)
<Preparation of raw material powder>
The raw material powder includes a metal powder. The metal powder is preferably made of a metal that is neither too soft nor too hard. Since the metal powder is not too hard, it is easily plastically deformed by pressure compression. Therefore, it is easy to obtain a dense powder compact having a relative density of 93% or more. Since the metal powder is not too soft, it is easy to obtain a powder compact having a relative density of 99.9% or less, that is, a powder compact containing pores.

The raw material powder may contain a metal powder having an appropriate composition depending on the composition of the matrix of the sintered metal material. Further, the hardness of the metal powder may be adjusted according to the composition of the metal powder. Adjustment of the hardness of the metal powder includes, for example, adjusting the composition of the metal powder, heat-treating the metal powder, adjusting the heat treatment conditions of the metal powder, and the like. For the composition of the metal powder, refer to the section of (Composition) of (Sintered metal material) described above.

For example, when the matrix of the sintered metal material is made of an iron-based material, the raw material powder includes a powder made of an iron-based material. Hereinafter, the powder made of an iron-based material may be referred to as "iron-based powder". The iron-based material is pure iron or an iron-based alloy. If the iron-based material is particularly an iron-based alloy, a high-strength sintered metal material can be obtained as described above. The iron-based powder can be produced by, for example, a water atomizing method, a gas atomizing method, or the like. Further, for example, when the matrix of the sintered metal material is made of pure titanium or a titanium-based alloy, the raw material powder includes a powder made of pure titanium or a titanium-based alloy.

The Vickers hardness Hv of the metal powder is preferably 80 or more and 200 or less. By using a metal powder having a Vickers hardness Hv satisfying the above range, the above-mentioned dense powder compact can be easily obtained. A metal powder having a Vickers hardness Hv of 80 or more is not too soft. By using the raw material powder containing such a metal powder, a powder compact having pores is obtained as described above. A metal powder having a Vickers hardness Hv of 200 or less is not too hard. By using the raw material powder containing such a metal powder, a dense powder compact can be obtained as described above. The Vickers hardness Hv may be 90 or more and 190 or less, 100 or more and 180 or less, and 110 or more and 150 or less.

When the matrix of the sintered metal material is made of an iron-based alloy, the raw material powders include, for example, the following.
(1) The raw material powder includes the first alloy powder. The first alloy powder is made of an iron-based alloy having the same composition as the iron-based alloy constituting the parent phase.
(2) The raw material powder includes a second alloy powder and a first element powder. The second alloy powder is composed of an iron-based alloy containing some of the additive elements contained in the iron-based alloy constituting the parent phase. The first element powder is a powder composed of each of the remaining additive elements among the above additive elements.
(3) The raw material powder includes the above-mentioned second alloy powder and the third alloy powder. The tertiary alloy powder is composed of an iron-based alloy containing the remaining additive elements among the above additive elements.
(4) The raw material powder includes pure iron powder and second element powder. The second element powder is a powder composed of each of all the additive elements in the iron-based alloy constituting the mother layer.

Specific examples of the raw material powder shown in (2) above will be described. For example, when the matrix of the sintered metal material is an iron-based alloy containing C, Ni, and Mo as additive elements and the balance is Fe and impurities, the raw material powders are the following second alloy powder and the first It may contain elemental powder. The second alloy powder is a powder containing the above-mentioned additive elements other than C, that is, Ni and Mo, and the balance is Fe and impurities. The first element powder is a carbon powder. As an example of the iron-based alloy, it is mentioned that it contains at least one element of Mo of 0.1% by mass or more and 2.0% by mass or less and Ni of 0.5% by mass or more and 5.0% by mass or less. The iron-based alloy containing Mo and Ni in the above range has various compositions having a Vickers hardness Hv of 80 or more and 200 or less. Therefore, it is easy to obtain a powder made of the above iron-based alloy.

The size of the raw material powder can be appropriately selected. The average particle size of the above-mentioned alloy powder or pure iron powder is, for example, 20 μm or more and 200 μm or less, and further 50 μm or more and 150 μm or less. The average particle size of the third powder (excluding carbon powder) is, for example, about 1 μm or more and 200 μm or less. The average particle size of the carbon powder is, for example, about 1 μm or more and 30 μm or less. The average particle size of the powder here is the particle size (D50) at which the cumulative volume in the volume particle size distribution measured by the laser diffraction type particle size distribution measuring device is 50%.

<Molding>
The higher the relative density of the dust compact, the higher the relative density of a dense sintered metal material. Therefore, finally, a spring made of a dense sintered metal material having a high relative density is obtained. A dense sintered metal material has few pores and tends to have small pores. The relative density of the dust compact is 93% or more and 99.9% or less. By using a dense powder compact with a relative density of 93% or more as a material, the relative density is 93% or more and 99.9% or less even at a relatively low temperature such as a sintering temperature of less than the liquid phase temperature. A certain dense sintered metal material is obtained. Further, the above-mentioned powder compact has pores in the range of 0.1% or more and 7% or less. However, each pore is reduced by pressure compression. By sintering the above-mentioned dense powder compact at a relatively low temperature, a dense sintered metal material having few pores and small size can be obtained. So to speak, a sintered metal material in which the size and amount of pores contained in the powder compact is substantially maintained can be obtained. Since this sintered metal material has few pores and is small, the pores are unlikely to be the starting points of cracks and are excellent in strength. Therefore, the strength of the spring can be increased.

The relative density of the powder compact may be 94% or more, further 96% or more, 96.5% or more, 97% or more, 98% or more. In order to increase the relative density of the powder compact, it is necessary to increase the molding pressure. However, if the molding pressure is too high, it may be difficult to take out the powder compact from the mold, the life of the mold may be shortened, and the productivity may be lowered. Therefore, from the viewpoint of productivity, the relative density of the powder compact may be 99.5% or less, further 99.4% or less, 99.2% or less, 99% or less. From the viewpoint of spring strength and productivity, the relative density of the dust compact is, for example, 94% or more and 99.5% or less, and further 94% or more and 99% or less.

The relative density (%) of the dust compact can be obtained by dividing the apparent density of the dust compact by the true density of the dust compact. The apparent density can be obtained by measuring the mass of the dust compact and dividing this mass by the volume of the dust compact. The true density can be determined from the composition of the raw material powder. The relative density of the powder compact may be obtained in the same manner as the relative density of the sintered metal material described above.

A mold press device is typically used for molding the powder compact. For molding the powder compact, for example, a cold isotropic pressurization (CIP) device can also be used. The shape of the mold may be selected according to the shape of the powder compact.

A lubricant may be applied to the inner peripheral surface of the mold. By applying the lubricant, it is possible to prevent the powder compact from being seized onto the mold. Therefore, in addition to being excellent in shape accuracy and dimensional accuracy, it is easy to obtain a dense powder compact. Examples of the lubricant include higher fatty acids, metal soaps, fatty acid amides, higher fatty acid amides and the like.

The higher the molding pressure, the easier it is to obtain a dense powder compact with a high relative density. The molding pressure is, for example, 1560 MPa or more. The molding pressure may be 1660 MPa or more, 1760 MPa or more, 1860 MPa or more, 1960 MPa or more. If the molding pressure is lowered, it becomes easier to take out the powder compact from the mold, the life of the mold is extended, and the productivity is improved.

The shape of the dust compact may be close to the shape of the spring or may be different from the shape of the spring. The shape of the powder compact may be, for example, a simple shape such as a cylinder, a cylinder, or a rectangular parallelepiped. If the shape of the dust compact is simple, it is easy to mold a dense dust compact with high accuracy even if the molding pressure is low to some extent. Further, if the shape is simple, the mold cost can be reduced.

As described above, the appearance of the spring 1 of the first embodiment is cylindrical. Therefore, when the spring 1 of the first embodiment is manufactured, for example, as shown in FIG. 3, the shape of the dust compact 101 may be cylindrical. If the shape of the dust compact 101 is cylindrical, it is close to the shape of the spring 1, so that less processing is required on the dust compact 101 in the second step.

(Second process: processing process)
The above-mentioned powder compact is cut into a spring shape. Examples of the cutting process include rolling processing and turning processing. Since it is processed into the shape of a spring by cutting, variations in dimensional accuracy can be suppressed. Therefore, a spring with high dimensional accuracy can be obtained, and stable spring characteristics can be obtained. Further, since the powder compact before sintering is a molded metal powder, it is easier to cut than a sintered metal material or a molten material after sintering. Therefore, the processing time can be shortened, and the life of the processing tool can be extended as compared with the case of processing a sintered metal material or a molten material. Therefore, the spring can be manufactured with high productivity by processing the dust compact into the shape of a spring. Further, since the cutting process can be easily performed, it is easy to obtain a spring having excellent dimensional accuracy.

The higher the relative density of the powder compact is to some extent, the easier it is to perform cutting. In particular, if the powder compact has a relative density of 93% or more, the cutting process can be performed satisfactorily even if the feed amount is set large, for example. Therefore, it is easy to obtain a spring having excellent dimensional accuracy. In this respect, the yield is improved. Further, if the feed amount is increased, the cutting time is shortened. In this way, cutting the powder compact has contributed to the improvement of spring productivity.

When the spring 1 of the first embodiment is manufactured, for example, the cylindrical dust compact 101 shown in FIG. 3 is cut to form a spiral shape forming the spring portion 10 as shown in FIGS. 1 and 2. The coil portion 10a is formed. Specifically, the coil portion 10a may be formed by cutting a spiral groove from the outer periphery of the powder compact 101 by cutting. The inner diameter and outer diameter of the powder compact 101 shown in FIG. 3 are constant over the entire length, and are equivalent to the inner diameter and outer diameter of the coil portion 10a shown in FIGS. 1 and 2. Therefore, when the spiral groove is machined on the powder compact 101 to form the coil portion 10a, the groove is machined at a constant depth. Examples of the tool used for machining the spiral groove include a machining tool such as an end mill, a side cutter, and a fly cut. In the processing of the spiral groove, for example, the tool is passed from the outer circumference to the inner circumference of the dust compact 101, and the tool is moved in the axial direction of the dust compact 101 while rotating the dust compact 101 around the central axis. It is possible to form a spiral groove. If the groove is machined to a certain depth, it is not necessary to change the depth position of the tool with respect to the outer peripheral surface of the powder compact 101 during the machining, and the machining is easy. Therefore, the spring 1 of the first embodiment in which the widths of the first spring portion 11 and the second spring portion 12 are constant can be efficiently manufactured.

In the case of the spring 1 of the first embodiment, as shown in FIG. 1, the spiral pitches in the coil portions 10a are uniform, that is, the coil portions 10a have equal pitches, and the intervals between adjacent turns in the spring portions 11 and 12 are equal. The size of the gap is different. Therefore, it is necessary to change the width of the spiral groove in each of the spring portions 11 and 12. When changing the groove width, for example, after forming a groove with a constant width by an end mill or the like, the side surface of the groove is cut to change the groove width. On the other hand, if the spiral pitches in the coil portions 10a are not uniform, that is, the coil portions 10a have unequal pitches and the sizes of the gaps between adjacent turns in the spring portions 11 and 12 are equal, the spiral groove The width can be constant. In this case, the thickness of each of the spring portions 11 and 12 in the vertical direction is changed while processing the groove with a constant width by an end mill or the like. When the groove width is constant, the processing man-hours can be reduced as compared with the case where the groove width is changed.

(Third process: sintering process)
The above-mentioned powder compact processed into the shape of a spring is sintered. The sintering temperature is preferably lower than the liquidus temperature. Specifically, when the metal powder is an iron-based powder, the sintering temperature is 1000 ° C. or higher and lower than 1300 ° C. The sintering temperature is lower than the liquidus temperature and is relatively low. Therefore, the thermal energy can be reduced as compared with the case of sintering at a high temperature such that a liquid phase is generated. Further, if the sintering temperature is relatively low, it is possible to suppress the formation of coarse pores. Therefore, it is easy to obtain a sintered metal material having small pores. Typically, a sintered metal material having an average peripheral length of pores of 100 μm or less or an average cross-sectional area of pores of 500 μm ^{2 or less can be obtained.} For example, by sintering a dense powder compact having a relative density of 93% or more at a relatively low temperature, a dense sintered metal material having few pores and small size can be obtained. Further, the low temperature sintering is less likely to cause a decrease in dimensional accuracy due to heat shrinkage than the high temperature sintering. Therefore, it is easy to obtain a spring having excellent dimensional accuracy, and the yield can be increased. As described above, sintering the powder compact at a relatively low temperature contributes to the improvement of spring productivity.

The sintering temperature and sintering time may be adjusted according to the composition of the raw material powder and the like. When iron-based powder is used, the sintering temperature is 1000 ° C. or higher and lower than 1300 ° C.

The lower the sintering temperature, the smaller the amount of heat shrinkage tends to be. Therefore, it is easy to obtain a spring having excellent dimensional accuracy. From the viewpoint of reducing thermal energy and improving dimensional accuracy, the sintering temperature is preferably 1250 ° C. or lower, more preferably less than 1200 ° C.

The higher the sintering temperature is within the above range, the shorter the sintering time tends to be. In this respect, productivity is increased. From the viewpoint of shortening the sintering time, the sintering temperature may be 1050 ° C. or higher, and further may be 1100 ° C. or higher.

From the viewpoint of reducing thermal energy and balancing good accuracy with shortening of sintering time, the sintering temperature is, for example, 1100 ° C. or higher and lower than 1200 ° C.

The sintering time is, for example, 10 minutes or more and 150 minutes or less.

Examples of the atmosphere at the time of sintering include a nitrogen atmosphere and a vacuum atmosphere. The vacuum atmosphere is, for example, 10 Pa or less. In a nitrogen atmosphere or a vacuum atmosphere, the oxygen concentration in the atmosphere is low, and it is easy to suppress the oxidation of the sintered metal material.

(Other processes)
The above-mentioned spring manufacturing method may include, after the third step, a step of heat-treating the sintered metal material obtained by sintering the above-mentioned dust compact. For example, in the case of a sintered metal material using the above-mentioned iron-based powder, the above-mentioned heat treatment includes, for example, carburizing treatment, quenching and tempering, and carburizing and quenching and tempering. The heat treatment conditions may be appropriately adjusted according to the composition of the sintered metal material. As the heat treatment conditions, known conditions can be applied.

The above-mentioned spring manufacturing method may include a step of finishing the sintered metal material after the third step. For example, finishing. Polishing, grinding, etc. can be mentioned. By performing the finishing process, a spring having excellent surface texture and a spring having higher shape accuracy and dimensional accuracy can be obtained.

(Main effect)
The spring 1 of the first embodiment is manufactured by cutting a powder compact before sintering and then sintering it. Since the spring 1 is processed into the shape of a spring by cutting, the variation in dimensional accuracy is small. Therefore, the spring 1 has high dimensional accuracy, and it is easy to obtain predetermined spring characteristics.

In the spring 1 of the first embodiment, the spring portion 10 includes a first spring portion 11 and a second spring portion 12. The first spring portion 11 and the second spring portion 12 have different cross-sectional areas. Therefore, the spring 1 has a non-linear characteristic.

The method for manufacturing a spring according to the first embodiment can manufacture a spring made of a sintered metal material. In this manufacturing method, since the powder compact is processed into the shape of a spring, variations in dimensional accuracy can be suppressed and the spring can be manufactured with high productivity. Further, according to this manufacturing method, a spring having a non-linear characteristic can be obtained.

[Embodiment 2]
In the first embodiment, with reference to FIGS. 1 and 2, the embodiment in which the spring portion 10 has one each of the first spring portion 11 and the second spring portion 12 is illustrated. The arrangement order of the first spring portion 11 and the second spring portion 12 can be changed as appropriate. In the second embodiment, with reference to FIGS. 4 and 5, at least one of the first spring portion 11 and the second spring portion 12 is provided, and the other spring portion is provided between the one spring portion. Illustrate the form being used. The spring 2 of the second embodiment shown in FIGS. 4 and 5 is a coiled spring. Hereinafter, the differences from the above-described first embodiment will be mainly described, and the same matters will be omitted.

In the spring 2 shown in FIGS. 4 and 5, the spring portion 10 has two second spring portions 12, and the first spring portion 11 is provided between the second spring portions 12. That is, in the spring portion 10, the second spring portion 12, the first spring portion 11, and the second spring portion 12 are arranged in this order from the upper end portion 21 side. The arrangement order of the first spring portion 11 and the second spring portion 12 is not limited to this.

4 and 5 show an example in which the first spring portion 11 is provided between the second spring portions 12, but the second spring portion 12 is between the first spring portions 11. It is also possible to change the order so that it is provided. That is, in the spring portion 10, the first spring portion 11, the second spring portion 12, and the first spring portion 11 may be arranged in this order. Further, a plurality of first spring portions 11 and a plurality of second spring portions 12 may be provided, and the first spring portions 11 and the second spring portions 12 may be arranged alternately.

[Embodiment 3]
In the first embodiment, with reference to FIGS. 1 and 2, the embodiment in which the thickness t _{12 of} the second spring portion 12 is larger than _{the thickness t 11 of} the first spring portion 11 is illustrated. In the third embodiment, with reference to FIGS. 6 and 7, an embodiment in which the width w _{12 of} the second spring portion 12 is larger than _{the width w 11 of} the first spring portion 11 is illustrated. The spring 3 of the third embodiment shown in FIGS. 6 and 7 is a coiled spring. Hereinafter, the differences from the above-described first embodiment will be mainly described, and the same matters will be omitted.

In the spring 3 shown in FIGS. 6 and 7, the first spring portion 11, the second spring portion 12, and the first spring portion 11 are arranged in this order from the upper end portion 21 side of the spring portion 10. As shown in FIG. 7, the spring 3 has a _{relative cross-sectional area of the second spring portion 12 because the width w 12} of the second spring portion 12 is larger than _{the width w 11 of} the first spring portion 11. It is set to large. In this example, the outer diameter of the coil portion 10a is not constant over the entire length. As shown in FIGS. 6 and 7, the outer diameter of the second spring portion 12 is larger than the outer diameter of the first spring portion 11. The inner diameter of the coil portion 10a is constant over the entire length of the coil portion 10a. _{The widths w 11} and w ₁₂ of the spring portions 11 and 12 may be appropriately set so as to have a cross-sectional area in which a predetermined spring characteristic can be obtained.

6, 7, the thickness t ₁₁ of the first spring portion 11 and the thickness t ₁₂ of the second spring portion 12 are substantially equal. _{The thicknesses t 11} and t ₁₂ of the first spring portion 11 and the second spring portion 12 may be different. For example, the thickness t _{12 of} the second spring portion 12 is larger than _{the thickness t 11 of} the first spring portion 11. When the thickness t ₁₂ and the width w ₁₂ of the second spring portion 12 are increased, the cross-sectional area of the second spring portion 12 becomes larger, so that the degree of freedom in designing the spring characteristics is increased.

When the spring 3 of the third embodiment is manufactured, the cylindrical dust compact is cut in the same manner as the spring 1 of the first embodiment, and the first spring portion 11 and the first spring portion 11 and the third shown in FIGS. 6 and 7 are cut. The second spring portion 12 is formed. For example, the inner and outer diameters of the powder compact to be molded may be equal to the inner and outer diameters of the second spring portion 12.

[Embodiment 4]
In the first embodiment, as shown in FIGS. 1 and 2, the shapes of the terminal portions 21 and 22 are cylindrical, and the inner and outer diameters of the terminal portions 21 and 22 are equivalent to the inner diameter and outer diameter of the coil portion 10a. The morphology was illustrated. In the fourth embodiment, examples of the shapes of the terminal portions 21 and 22 are shown with reference to FIGS. 8 and 10. The springs 4A and 4B shown in FIGS. 8 and 10 are coiled springs. Hereinafter, the differences from the above-described first embodiment will be mainly described, and the same matters will be omitted.

The spring 4A of the fourth embodiment shown in FIG. 8 has a flange 40 in which the terminal portion 22 projects radially with respect to the spring portion 10. In this example, as shown in FIG. 8, a through hole 41 penetrating in the axial direction is formed on the end surface of the flange 40. The flange 40 and the through hole 41 function as, for example, a mounting portion for mounting on a mating member (not shown).

When the spring 4A of the fourth embodiment is manufactured, for example, the dust compact 102 as shown in FIG. 9 may be cut. The dust compact 102 has a cylindrical main body 110 and a flange 120 that protrudes radially from the end of the main body 110. The flange 120 of the dust compact 102 is a portion corresponding to the flange 40 of the spring 4A.

In the spring 4B of the embodiment 4B shown in FIG. 10, the shape of the terminal portion 22 is cylindrical. In this example, as shown in FIG. 10, a through hole 42 penetrating in the radial direction is formed on the outer peripheral surface of the terminal portion 22. Further, a groove 43 along the radial direction is formed on the end surface of the terminal portion 22. The through hole 42 and the groove 43 function as, for example, an attachment portion for attaching to a mating member (not shown).

When the spring 4B of the fourth embodiment is manufactured, for example, the dust compact 103 as shown in FIG. 11 may be cut. The dust compact 103 has a cylindrical main body 110 and a cylindrical bottom 130 provided at the end of the main body 110. The bottom portion 130 of the dust compact 103 is a portion corresponding to the terminal portion 22 of the spring 4B.

[Modification example]
In the first embodiment, a mode in which the spring portion 10 is composed of one coil portion 10a has been described with reference to FIGS. 1 and 2. The spring portion 10 may have a configuration having a plurality of coil portions 10a. In this case, there is a form in which the coil portions 10a are provided so as not to intersect each other. By independently providing the plurality of coil portions 10a so as not to intersect each other, more complicated spring characteristics can be obtained. Further, by having a plurality of coil portions 10a, even if one coil portion 10a is damaged, the remaining coil portion 10a functions as a spring portion 10. Therefore, it is possible to prevent one coil portion 10a from being damaged and immediately becoming unusable. When the spring portion 10 is composed of a plurality of coil portions 10a, the number of coil portions 10a is, for example, 2 or more and 6 or less, and further 2 or more and 4 or less from the viewpoint of manufacturability.

When manufacturing a spring having a plurality of coil portions 10a, for example, a cylindrical dust compact is processed so that a plurality of spiral grooves do not intersect with each other. Specifically, the spiral grooves are formed so as to be out of phase with each other in the circumferential direction. As a result, a plurality of coil portions 10a can be formed. The number of spiral grooves may be appropriately determined according to the number of coil portions 10a to be formed. For example, if the number of spiral grooves is two, two coil portions 10a are formed.

In the above-described example, the mode in which the plurality of coil portions 10a do not intersect each other has been described, but the coil portions 10a may be provided so as to intersect each other. For example, there is a form in which two coil portions 10a are provided and the directions of the spirals of the coil portions 10a are opposite to each other.

[Embodiment 5]
In the first embodiment, as shown in FIGS. 1 and 2, the form of a coiled spring in which the spring portion 10 is composed of the coil portion 10a is illustrated. In the fifth embodiment, with reference to FIG. 12, an embodiment in which the spring portion 10 is composed of a pillar portion 10b that is curved in a curved shape is illustrated. That is, the spring 5 of the fifth embodiment shown in FIG. 12 is a so-called columnar spring. The appearance of the spring 5 is cylindrical. Hereinafter, the differences from the above-described first embodiment will be mainly described, and the same matters will be omitted.

The spring 5 shown in FIG. 12 can be elastically deformed with respect to a load because the pillar portion 10b constituting the spring portion 10 is curved in a curved shape. The pillar portion 10b has a first spring portion 11 and a second spring portion 12. In this example, as shown in FIG. 12, a second spring portion 12 is provided on each of the terminal portion 21 side and the terminal portion 22 side of the pillar portion 10b, and the first spring portion 11 is provided in the center between them. There is. That is, in the spring portion 10, the second spring portion 12, the first spring portion 11, and the second spring portion 12 are arranged in this order from the upper end portion 21 side. As shown in FIGS. 13A to 13C, the cross-sectional areas of the spring portions 11 and 12 are relatively small in the first spring portion 11 and relatively large in the second spring portion 12. ing.

In the case of this example, as shown in FIG. 12, the two pillar portions 10b are provided so that the pillar portions 10b do not intersect with each other. The pillar portions 10b are formed at intervals in the circumferential direction. Further, the pillar portion 10b is curved in a C shape. The shape of each pillar portion 10b is the same. The number and shape of the column portions 10b are not particularly limited, and may be appropriately set so as to obtain predetermined spring characteristics. The number of pillars 10b may be one or three or more.

When the spring 5 of the fifth embodiment is manufactured, for example, the cylindrical dust compact 101 shown in FIG. 3 is machined, and as shown in FIG. 12, the curved pillar portion 10b constituting the spring portion 10 is formed. To form. Specifically, the column portion 10b may be formed by removing a part from the outer periphery of the powder compact 101 by cutting.

In the above-described example, the mode in which the plurality of pillars 10b do not intersect each other has been described, but the pillars 10b may be provided so as to intersect or connect with each other. For example, the two pillars 10b may intersect in an X shape or may be connected in a diamond shape (pantograph shape). Further, each pillar portion 10b may have a bent linear shape, for example, a zigzag shape.

1, 2, 3, 4A, 4B, 5 Spring 10 Spring part 10a Coil part 10b Pillar part 11 First spring part 12 Second spring part 21, 22 Terminal part 31, 32 Connection part 40 Flange 41, 42 Through hole 43 Grooves 101, 102, 103 Powder compact 110 Main body 120 Flange 130 Bottom t ₁₁ , t ₁₂ Thickness w ₁₁ , w ₁₂ Width

Claims (13)

A spring portion and terminal portions provided at both ends of the spring portion are provided.
The spring portion and the terminal portion are integrally formed of a sintered metal material.
The spring portion includes a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.
Spring. The spring according to claim 1, wherein the spring portion is composed of at least one coil portion formed in a spiral shape. According to claim 2, in the cross section including the central axis of the coil portion, the vertical thickness of the second spring portion along the central axis is larger than the vertical thickness of the first spring portion. The spring described. The spring according to claim 3, wherein the width of the first spring portion and the second spring portion in the lateral direction orthogonal to the central axis is constant in a cross section including the central axis of the coil portion. Claim 2 or claim that the lateral width of the second spring portion orthogonal to the central axis is larger than the lateral length of the first spring portion in the cross section including the central axis of the coil portion. Item 3. The spring according to item 3. The spring portion has a plurality of the coil portions, and the spring portion has a plurality of the coil portions.
The spring according to any one of claims 2 to 5, wherein the plurality of coil portions are provided so as not to intersect each other. The spring according to claim 1, wherein the spring portion is composed of at least one pillar portion that curves in a curved shape. The spring portion has a plurality of the pillar portions, and the spring portion has a plurality of the pillar portions.
The spring according to claim 7, wherein the plurality of pillars are provided so as not to intersect each other. The spring according to any one of claims 1 to 8, wherein the connecting portion between the spring portion and the terminal portion has a curved surface. The spring according to any one of claims 1 to 9, wherein the relative density of the sintered metal material is 93% or more and 99.9% or less. The sintered metal material has a matrix made of an iron-based alloy and has a matrix.
Any one of claims 1 to 10, wherein the iron-based alloy contains one or more elements selected from the group consisting of Cu, Cr, Ni, Mo, Mn, P, Si, B and C. The spring described in. The spring according to any one of claims 1 to 10, wherein the sintered metal material has a matrix made of pure titanium or a titanium-based alloy. A process of forming a powder compact by pressurizing and compressing a raw material powder containing a metal powder,
The process of cutting the powder compact to form a spring shape,
The step of sintering the powder compact processed into the shape of a spring is provided.
The shape of the spring is
It integrally has a spring portion and terminal portions provided at both ends of the spring portion.
The spring portion has a shape including a first spring portion having a relatively small cross-sectional area and a second spring portion having a relatively large cross-sectional area.
How to make a spring.

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