coil spring

Abstract

According to one embodiment, a helical spring is composed of a line (2) having one end and the other end. The line (2) of the helical spring has a cross-section comprising an effective portion (13) consisting of a circular cross-section portion (30), a square cross-section portion (31) having a substantially square cross-section and including a coil portion (11) (12), and a tapered portion (32). One side length of the cross-section of the square cross-section portion (31) is less than or equal to the square root of the diameter of the line (2) of the circular cross-section portion (30). The tapered portion (32) changes from a circular cross-section portion (30) to a substantially square cross-section portion (31), and the cross-sectional area decreases.

Description

Technical Field

[0001] The present invention relates to coil springs used, for example, in vehicle suspension systems. Background Technology

[0002] An example of a coil spring used in a vehicle suspension system is composed of a wire rod wound into a spiral shape. The cross-section of the wire rod (a cross-section perpendicular to the length direction of the wire rod) is generally circular. The coil spring has a first coil portion that contacts a first spring seat in the suspension system, a second coil portion that contacts a second spring seat, and an effective portion between the first and second coil portions.

[0003] The effective portion has multiple coil portions. When the helical spring is compressed to a specified length under load, gaps exist between the coil portions of the effective portion. The seat coil portion remains in contact with the spring seat regardless of the load magnitude. A portion of the effective portion contacts or leaves the spring seat depending on the load magnitude.

[0004] The coil spring extends and contracts with a specified stroke between the intended minimum and maximum loads. Some vehicles may require coil springs with nonlinear characteristics. The spring constant of a nonlinear coil spring varies depending on the load. For example, when the load is small, the coil spring flexes with a first spring constant, and when the load increases, it flexes with a second spring constant. The second spring constant is greater than the first spring constant.

[0005] A conical helical spring with a tapered portion is also known, wherein the diameter of the conductor decreases from the middle of the effective portion toward the end of the conductor. Because the tapered portion has low rigidity, the conical portion of the helical spring primarily deflects in the low-load region. As the load increases, the effective portion deflects due to the tapered portion becoming tightly closed, thus exhibiting nonlinear characteristics.

[0006] The diameter of the linear wire of the conical coil spring described in Japanese Patent Application Publication No. 57-11743 (reference document 1) decreases from the middle of the effective part toward the seat coil part. The cross-section of the linear wire of the conical coil spring described in Japanese Patent Application Publication No. 56-141431 (reference document 2) is approximately circular with an octagonal shape with an arc.

[0007] Existing technical documents

[0008] Patent documents

[0009] [Comparison Document 1] Japanese Patent Application Publication No. 57-11743

[0010] [Comparison Document 2] Japanese Patent Application Publication No. 56-141431

[0011] [Comparative Document 3] Japanese Patent Application Publication No. 2000-337415

[0012] [Comparison Document 4] Japanese Patent Application Publication No. 54-52257. Summary of the Invention

[0013] [Unresolved Issues in the Invention]

[0014] In a helical spring composed of a roughly circular cross-section wire, the portion with an extremely small wire diameter is difficult to process. For example, special calendering rolls are required to make the wire diameter sufficiently small through plastic forming. Although the wire diameter can be reduced by cutting or swaging, the high cost and long processing time make it impractical. For these reasons, it is difficult to make a portion of the wire diameter extremely small.

[0015] In nonlinear helical springs, even with limitations on reducing the wire diameter of the tapered and small-section portions (small-diameter portions), it is possible to increase the number of turns in these portions and reduce the spring constant in low-load areas. However, the tapered and small-section portions of nonlinear helical springs become tightly wound when the load increases. These tightly wound portions become dead coils that fail to function as springs. Helical springs with a high number of dead coils contribute to increased vehicle weight.

[0016] The helical springs described in Japanese Patent Application Publication No. 2000-337415 (reference document 3) and Japanese Patent Application Publication No. 54-52257 (reference document 4) have a flat portion with a rectangular cross-section formed by rolling a portion (including the coiled portion) along the length of the raw wire. The flat portion with a rectangular cross-section can be easily formed using ordinary calendering rolls. However, compared to a raw wire with a circular cross-section, the polar moment of inertia of area in the flat portion is particularly large. Therefore, even if the desired nonlinear characteristics are obtained, it is difficult to reduce the weight of the helical spring with the nonlinear characteristics of the flat portion.

[0017] The purpose of this invention is to provide a helical spring with nonlinear characteristics and light weight.

[0018] [Methods for solving the problem]

[0019] One embodiment of the present invention is a helical spring composed of a single wire having one end and another end, comprising a first end turn part including the one end of the single wire, a second end turn part including the other end of the single wire, and an effective spring part. The effective spring part has a plurality of coil portions formed between the first and second end turn parts, with gaps between adjacent coil portions. The effective spring part includes a circular cross-section portion having a first cross-section perpendicular to the length direction of the single wire.

[0020] Furthermore, the helical spring of this embodiment has a square cross-section portion extending beyond the first coil portion from one end of the generatrix, and a tapered portion with a length of 1.0 coil or more formed between the circular cross-section portion and the square cross-section portion. The second cross-section of the square cross-section portion, perpendicular to the length direction, is substantially square, and the length of one side of the second cross-section is less than half the root (√) of the diameter of the generatrix of the circular cross-section portion, and the second cross-section is constant in the length direction. The cross-section of the tapered portion (the third cross-section perpendicular to the length direction of the generatrix) changes from a circle to a substantially square and the cross-sectional area decreases from the circular cross-section portion toward the square cross-section portion.

[0021] The square cross-section portion may include a first surface on the outer side and a second surface on the inner side along the central axis of the helical spring, and a third surface on the upper side and a fourth surface on the lower side that are perpendicular to and parallel to the first and second surfaces. In the helical spring of this embodiment, the square cross-section portion has at least a first coil portion and a second coil portion, and in the compressed state of the helical spring, it may also have an abutting portion where the third surface of the first coil portion and the fourth surface of the second coil portion contact each other. The coil diameter of the second coil portion of the square cross-section portion may also be smaller than the coil diameter of the second coil portion.

[0022] The tapered portion includes a first planar portion connected to the first surface of the square cross-section portion, a second planar portion connected to the second surface, a third planar portion connected to the third surface, a fourth planar portion connected to the fourth surface, a first arc portion located between the first and third planar portions, a second arc portion located between the first and fourth planar portions, a third arc portion located between the second and third planar portions, and a fourth arc portion located between the second and fourth planar portions.

[0023] [The effects of the invention]

[0024] The square cross-section can be easily processed using calendering rolls or similar methods. It is also not difficult to significantly reduce the cross-sectional area of ​​the square cross-section compared to that of the circular cross-section. Attached Figure Description

[0025] Figure 1 This is a perspective view of the helical spring according to the first embodiment.

[0026] Figure 2 yes Figure 1 The diagram shows a three-dimensional view of a portion of a coil spring in its compressed state, represented by a cross-section.

[0027] Figure 3 This is a side view of a portion of the line of the coiled spring before it is wound.

[0028] Figure 4 This is a cross-sectional view schematically representing an example of a square cross-section of the generatrix.

[0029] Figure 5 These are the quadratic polar moment diagrams of three generatrices with different cross-sections.

[0030] Figure 6 yes Figure 1 The diagram shows the spring characteristics (relationship between deflection and load) of a helical spring.

[0031] Figure 7 This is a graph showing the relationship between the position of the lower end of the coil spring and the stress (inner side of the coil).

[0032] Figure 8 It is a schematic three-dimensional diagram representing the rolling mill.

[0033] Figure 9 This is a top view of a part of the edge-rolling machine.

[0034] Figure 10 This is a perspective view of the helical spring according to the second embodiment.

[0035] Figure 11 yes Figure 10 A three-dimensional view of a portion of a helical spring, shown in cross-section.

[0036] [Explanation of Symbols]

[0037] 1,1A…coil spring, 2…generic wire, 11…first winding section, 12…second winding section, 13…effective section, 13a…winding section, 30…circular cross-section section, 31…square cross-section section, 31a…first surface, 31b…second surface, 31c…third surface, 31d…fourth surface, S1…first section, S2…second section, S3…third section, 32…conical section, 32a…first planar section, 32b…second planar section, 32c…third planar section, 32d…fourth planar section, 32e…first arc section, 32f…second arc section, 32g…third arc section, 32h…fourth arc section, C1…central shaft, 41…first winding section, 42…second winding section, 43…contact section. Detailed Implementation

[0038] The following is for reference Figures 1-9 A helical spring according to one embodiment of the present invention will be described.

[0039] Figure 1 This refers to a coil spring 1 used in the suspension system of vehicles such as automobiles. The coil spring 1 has a wire rod 2 wound into a helical shape. The wire rod 2 is made of, for example, spring steel. The coil spring 1 has a first coil portion 11 including one end 2a of the wire rod 2, a second coil portion 12 including the other end 2b of the wire rod 2, and an effective portion 13. The effective portion 13 is formed between the first coil portion 11 and the second coil portion 12 and has multiple winding portions 13a. When the coil spring 1 is embedded in the suspension system of a vehicle, the first coil portion 11 is located on the upper side, and the second coil portion 12 is located on the lower side. In this case, the central axis C1 of the coil spring 1 extends in the vertical direction.

[0040] An example of effective part 13 is the spacing P1 (e.g. Figure 1 (As shown) A cylindrical shape with a constant coil diameter R1. Here, "substantially constant" means that the deviation within the tolerance range of the helical spring manufactured by the crimping machine, or the deviation within the allowable range caused by springback, is practically negligible. Alternatively, the pitch P1 and coil diameter R1 can also be a non-cylindrical helical spring that varies along the central axis C1.

[0041] The first seat 11 is supported by a spring seat 20 on the upper side of the suspension device (such as...). Figure 2 (As shown) Support. Figure 1 As shown, the second coil portion 12 is supported by the spring seat 21 on the lower side of the suspension device. The coil spring 1 is compressed between the upper spring seat 20 and the lower spring seat 21. When the coil spring 1 is compressed within a specified load range (the range of loads used by the suspension device), the effective portion 13 has a gap G1 between adjacent coil portions 13a.

[0042] The coil spring 1 used in the vehicle suspension system is used within a load range between the intended minimum and maximum load. The effective portion 13 functions effectively as a spring in either the fully compressed (full bump) state or the fully extended (full rebound) state, with adjacent coil portions 13a not contacting each other.

[0043] Figure 2 This is a perspective view showing a portion (near the seat coil portion 11) of the helical spring 1 in a compressed state. The helical spring 1 of this embodiment includes a circular cross-sectional portion 30 of the effective portion 13, a square cross-sectional portion 31 of the first seat coil portion 11, and a tapered portion 32 formed between the circular cross-sectional portion 30 and the square cross-sectional portion 31. The first seat coil portion 11 has a square cross-sectional portion 31 and is shaped into a spiral. The second seat coil portion 12 has a portion of the circular cross-sectional portion 30 and is shaped into a spiral. The effective portion 13 is composed of the circular cross-sectional portion 30 and has a plurality of spirally wound portions 13a.

[0044] Figure 3 This shows a portion of the element 2 before it is wound up. The axis X1, passing through the center of the element 2, extends along the length of the element 2. Figure 3 The shown line 2 has a circular cross-section portion 30 of length L1, a square cross-section portion 31 of length L2, and a tapered portion 32 of length L3. The circular cross-section portion 30 has a plurality of winding portions 13a of effective portion 13, which are required to reach the length L1. The square cross-section portion 31 extends from one end 2a of the line 2 across the length L2. The tapered portion 32 is formed between the circular cross-section portion 30 and the square cross-section portion 31, extending across the length L3.

[0045] like Figure 2 As shown, the cross-section of the circular cross-section portion 30 (the first cross-section S1 perpendicular to the axis X1 of the generatrix 2) is circular. Furthermore, the first cross-section S1 is substantially constant along the length direction of the generatrix 2 (along the axis X1). The second roll portion 12 is formed from a portion of the circular cross-section portion 30, and therefore its cross-section is circular. The diameter of the generatrix of the second roll portion 12 is the same as the diameter of the generatrix of the circular cross-section portion 30 of the effective portion 13.

[0046] The square cross-section portion 31 includes a portion along the central axis C1 of the helical spring 1 (e.g., Figure 1 and Figure 2The outer first surface 31a and the inner second surface 31b (shown), the upper third surface 31c and the lower fourth surface 31d (perpendicular to the first surface 31a). The third surface 31c and the fourth surface 31d are planes that are almost perpendicular to the central axis C1 of the coil spring 1. The square cross-section portion 31 has a first winding portion 41 and a second winding portion 42. The coil diameter r2 of the second winding portion 42 is smaller than the coil diameter r1 of the first winding portion 41.

[0047] Figure 2 The diagram shows the state in which the helical spring 1 is compressed by a load along the central axis C1. When the helical spring 1 is compressed, the upper surface 31c of the first winding portion 41 and the lower surface 31d of the second winding portion 42 of the square cross-section portion 31 overlap in the direction along the central axis 1c of the helical spring 1. Therefore, a contact portion 43 is formed. Thus, it is possible to prevent the second winding portion 42 from entering (slipping into) the inside of the first winding portion 41.

[0048] The cross-section of the square section 31 (the second cross-section S2 perpendicular to the axis X1) is substantially square (approximately square). However, the term "substantially square (approximately square)" in this specification does not refer to a square in the strictly geometric sense. For example... Figure 4 The second section S2 is schematically shown. The lengths T1, T2, T3, and T4 of each of the four sides A1, A2, A3, and A4 of the section are equal within the machining tolerance. The lengths T1, T2, T3, and T4 of each side A1, A2, A3, and A4 are each less than √5 times the diameter D1 of the circular section 30.

[0049] The interior angles θ1, θ2, θ3, and θ4 formed by the sides A1, A2, A3, and A4 are almost 90° within the machining tolerance range. At the intersections of the sides A1, A2, A3, and A4, rounded corners B1, B2, B3, and B4 can also be formed. The second section S2 is essentially constant along the length of generatrix 2 (along the axis X1).

[0050] The cross-section of the tapered portion 32 (the third cross-section S3 perpendicular to the axis X1) gradually changes from a circular cross-section portion 30 to a roughly square cross-section portion 31, and the cross-sectional area decreases. The tapered portion 32 forms a roll of 1.0 or more between the circular cross-section portion 30 and the square cross-section portion 31.

[0051] like Figure 2As shown, the cross-section (third cross-section S3) of the tapered portion 32 includes a first planar portion 32a, a second planar portion 32b, a third planar portion 32c, a fourth planar portion 32d, a first arc portion 32e, a second arc portion 32f, a third arc portion 32g, and a fourth arc portion 32h. The first planar portion 32a is connected to the first surface 31a of the square cross-section portion 31. The first planar portion 32a is along the central axis C1 of the helical spring 1.

[0052] The second planar portion 32b is connected to the second surface 31b of the square cross-section portion 31. The second planar portion 32b is along the central axis C1 of the helical spring 1. The third planar portion 32c is connected to the third surface 31c of the square cross-section portion 31. The third planar portion 32c is perpendicular to the first planar portion 32a. The fourth planar portion 32d is connected to the fourth surface 31d of the square cross-section portion 31. The fourth planar portion 32d is perpendicular to the first planar portion 32a.

[0053] The first arc portion 32e is formed by an arc-shaped curved surface between the first plane portion 32a and the third plane portion 32c. The second arc portion 32f is formed by an arc-shaped curved surface between the first plane portion 32a and the fourth plane portion 32d. The third arc portion 32g is formed by an arc-shaped curved surface between the second plane portion 32b and the third plane portion 32c. The fourth arc portion 32h is formed by an arc-shaped curved surface between the second plane portion 32b and the fourth plane portion 32d. These arc portions 32e, 32f, 32g, and 32h are respectively connected to the corner portions B1, B2, B3, and B4 of the square cross-section portion 31 (e.g., ...). Figure 4 (as shown) connected.

[0054] Figure 5 The relationship between the position of three generatrices with different cross sections along their respective length directions and the second polar moment (torsional stiffness) of the cross section is shown. Figure 5 The solid line M1 in the figure shows the element line 2 according to this embodiment (e.g. Figure 3 The quadratic polar moment of the cross-section shown is [not shown]. In this embodiment, the generatrix diameter of the circular cross-section 30 is 15.4 mm, and the side length of the square cross-section 31 is 6 mm. Figure 5 In the diagram, length L3a, starting from zero (0) on the horizontal axis, is the second polar moment of the tapered portion 32, and length L2a is the second polar moment of the square cross-section portion 31. The second polar moment of the square cross-section portion 31 is much smaller than that of the circular cross-section portion 30.

[0055] Figure 5The two-dotted line M2 in the figure illustrates the second polar moment of the cross section of the generatrix of Conventional Example 1, which has a flat taper portion. The generatrix in Conventional Example 1 has a flat taper portion of length L4, extending from the end of a circular cross-section with a diameter of 15.4 mm to the front end of the generatrix. The cross-section of the flat taper portion is a flat rectangle. The end face of the flat taper portion has a width of 15.4 mm and a thickness of 5.5 mm.

[0056] The quadratic moment of the cross section (dotted line M2) of the conventional example 1 with the planar tapered portion is significantly larger than the quadratic moment of the cross section (solid line M1) of this embodiment. To reduce the first spring constant of the helical spring in the conventional example 1 with the planar tapered portion, the number of turns in the planar tapered portion needs to be increased. Therefore, in the second spring constant domain, the more turns of the dead coil, the greater the weight.

[0057] Figure 5 The dashed line M3 in the figure shows the second polar moment of the cross section of the generatrix of conventional Example 2, which has a round taper portion. The generatrix of conventional Example 2 has a round taper portion of length L3a starting from one end of the round taper portion and a smaller cross section of length L2a (generatrix diameter 11.4 mm). The generatrix diameter of the round taper portion is 15.4 mm.

[0058] The quadratic moment of polarity of the cross section in Conventional Example 2 (dashed line M3) is greater than that in this embodiment (solid line M1). To reduce the first spring constant of the helical spring in Conventional Example 2 with its circular conical portion, the number of turns in the circular conical portion needs to be increased. Therefore, in the second spring constant domain, the more turns the dead coil has, the greater the weight.

[0059] If the quadratic moments of each section of the square and circular cross-sections are the same, then the side length of one side of the square cross-section is approximately 0.87-0.89 times the diameter of the circular cross-section, a very small difference. There is little difference in torsional stiffness between circular and square cross-sections of equivalent size. It is not easy to machine a circular cross-section into a circular cone with a very small diameter. Conversely, the square cross-section portion 31 can be machined relatively easily using at least a pair of calendering rolls. In practical applications, the square cross-section portion can also be plastically processed so that the side length of one side is less than the square root of the diameter of the circular cross-section portion.

[0060] Figure 6 The spring characteristics (relationship between load and deflection) of the helical spring 1 according to this embodiment are schematically shown. Figure 6 The horizontal axis represents deflection, and the vertical axis represents load. The coil spring 1 has a spring seat 21 on the lower side (as shown in the image). Figure 1 (as shown) and the upper spring seat 20 (as shown) Figure 2The section 31 (as shown) is compressed. Between loads of 0 and W1, the square section 31 mainly flexes.

[0061] Therefore, as Figure 6 As shown by line K1, this becomes the first spring constant domain E1, where the spring constant is relatively small. When the load exceeds W1, the square section 31 becomes a closed state, while the circular section 30 mainly bends. Therefore, as... Figure 6 As shown by line K2, the spring constant increases (second spring constant domain E2).

[0062] Figure 7 The diagram illustrates the relationship between the stress generated inside the coil spring 1 when the coil spring 1 is compressed and the position from the lower end of the coil spring 2. Peak stress τmax is generated in each winding portion 13a of the effective portion 13. These peak stress τmax are less than the allowable stress in the suspension system. A small peak stress τ1 is generated near the seat winding portion 11.

[0063] According to the inventor's in-depth research, when the number of rolls of the tapered portion 32 is less than 1.0, such as Figure 7 As shown in τ2, the stress in the tapered portion 32 exceeds the peak stress τmax of the effective portion 13. It is not preferable for the stress in the tapered portion 32 to exceed the stress in the effective portion 13. Therefore, in this embodiment, the number of rolls in the tapered portion 32 is greater than or equal to 1.0.

[0064] Figure 8 A calendering apparatus 50 is schematically shown, forming a square cross-section portion 31 and a tapered portion 32 on a raw wire 2 with a circular cross-section. The raw wire 2 moves in the direction indicated by arrow F1. The calendering apparatus 50 has calendering rollers 51 and 52. The spacing between the calendering rollers 51 and 52 is adjustable. The raw wire 2 is calendered by the calendering rollers 51 and 52. Then, the raw wire 2 is rotated 90° about axis X1, and the raw wire 2 is calendered again by the calendering rollers 51 and 52.

[0065] Figure 9 A portion of a winding machine 60 is shown, which shapes a helical spring in a hot zone (e.g., above the A3 anomalous point and below 1150°C). The winding machine 60 includes a cylindrical drum 61, a gripper 62, and a guide section 63. The guide section 63 includes a pair of first guide rollers 65, 66.

[0066] The raw wire 2, made of spring steel, is pre-cut to the length of a helical spring. The raw wire 2 is heated to its austenitizing temperature (above the A3 metamorphic point and below 1150°C) and fed to the drum 61 by a feeding mechanism. A gripper 62 secures the front end of the raw wire 2 to the drum 61. A guide 63 controls the position of the raw wire 2 wound on the drum 61 by guiding the raw wire 2.

[0067] One end 61a of the drum 61 is held on the drive head 70 by a gripper 62. The drum 61 rotates about axis X2 via the drive head 70. The other end 61b of the drum 61 is rotatably supported by a drum holder 71. The guide 63 moves along the axis X2 of the drum 61 and guides the generatrix 2 according to the pitch angle of the helical spring to be formed.

[0068] The main thread 2 is equivalent to the length of a helical spring. Before being fed to the drum 61, the main thread 2 is heated in a furnace. The heated end of the main thread 2 is then fixed to the drum 61 by a gripper 62. As the drum rotates, the guide 63 moves along the axis X2 of the drum 61 to synchronize with its rotation. Thus, the main thread 2 is wound onto the drum 61 with a predetermined pitch.

[0069] The following comparative examples 1, 2, 3, and 4 describe helical springs having nonlinear characteristics, including an effective portion with a circular cross-section, a circular conical portion, and a small cross-section. In contrast, Examples 1, 2, 3, and 4 respectively have... Figure 1 The helical spring shown has the same nonlinear characteristics as the circular cross-section 30, square cross-section 31, and tapered section 32 as the helical spring 1 shown.

[0070] [Compare with Example 1]

[0071] The diameter of the wire in the circular section of the helical spring in Example 1 is 18 mm, the diameter of the wire in the small section is 13 mm, the total number of turns is 8.5, and the weight is 7.0 kg.

[0072] [Example 1]

[0073] The helical spring of Example 1 has a circular cross-section portion 30 with a wire diameter of 18 mm, a square cross-section portion 31 with a side length of 7 mm, and a total of 8.5 turns. One side length of the square cross-section portion 31 is 40% of the wire diameter of the circular cross-section portion 30. The spring characteristics (load-deflection relationship) of Example 1 are the same as those of Comparative Example 1. The helical spring of Example 1 weighs 5.2 kg, which is approximately 24% lighter than the helical spring of Comparative Example 1.

[0074] [Compare with Example 2]

[0075] The diameter of the wire in the circular section of the helical spring in Example 2 is 15 mm, the diameter of the wire in the small section is 11 mm, the total number of turns is 8.5, and the weight is 7.0 kg.

[0076] [Example 2]

[0077] The helical spring of Example 2 has a circular cross-section portion 30 with a wire diameter of 15 mm, a square cross-section portion 31 with one side length of 7 mm, and a total number of turns of 9.0. The side length of one side of the square cross-section portion 31 is 47% of the wire diameter of the circular cross-section portion 30. The spring characteristics of Example 2 are the same as those of Comparative Example 2. The helical spring of Example 2 weighs 4.0 kg, which is approximately 23% lighter than the helical spring of Comparative Example 2.

[0078] [Compare with Example 3]

[0079] The diameter of the wire in the circular section of the helical spring in Example 3 is 22 mm, the diameter of the wire in the small section is 17 mm, the total number of turns is 8.0, and the weight is 8.5 kg.

[0080] [Example 3]

[0081] The helical spring of Example 3 has a circular cross-section portion 30 with a wire diameter of 22 mm, a square cross-section portion 31 with one side length of 7 mm, and a total number of turns of 8.0. The side length of one side of the square cross-section portion 31 is 32% of the wire diameter of the circular cross-section portion 30. The spring characteristics of Example 3 are the same as those of Comparative Example 3. The helical spring of Example 3 weighs 6.5 kg, which is approximately 22% lighter than the helical spring of Comparative Example 3.

[0082] [Compare with Example 4]

[0083] The diameter of the wire in the circular section of the helical spring in Example 4 is 16 mm, the diameter of the wire in the small section is 12 mm, the total number of turns is 10.0, and the weight is 6.0 kg.

[0084] [Example 4]

[0085] The helical spring of Example 4 has a circular cross-section portion 30 with a wire diameter of 15 mm, a square cross-section portion 31 with one side length of 7 mm, and a total number of turns of 9.0. The side length of one side of the square cross-section portion 31 is 47% of the wire diameter of the circular cross-section portion 30. The spring characteristics of Example 4 are the same as those of Comparative Example 4.

[0086] The weight of the helical spring in Example 4 is 5.0 kg, which is about 18% lighter than that in Comparative Example 4.

[0087] In the helical springs of Examples 1-4, the side length of one side of the square cross-section 31 is less than 50% of the generatrix diameter of the circular cross-section 30. While the side length of the square cross-section 31 may fluctuate slightly during its formation, it is possible to reduce its weight by nearly 20% compared to conventional helical springs by setting the side length of the square cross-section to be less than the square root of the generatrix diameter of the circular cross-section.

[0088] Figure 10 A helical spring 1A according to the second embodiment is shown. Figure 11 This is a perspective view showing a cross-section of a portion of the coil spring 1A (near the coil section 11). The coil spring 1A has a square cross-section portion 31 with two or more coils and a tapered portion 32 with one or more coils. The cross-section of the main wire of the second coil section 12 is circular. The diameter of the main wire of the second coil section 12 is the same as the diameter of the main wire of the circular cross-section portion 30. The second coil section 12 has a small-diameter winding portion 90 whose coil diameter decreases toward the other end 2b of the main wire 2. The diameter of the main wire of the second coil section 12 can be smaller than the diameter of the main wire of the circular cross-section portion 30.

[0089] The square cross-section 31 of the first winding portion 11 of the helical spring 1A has at least a first winding portion 41 and a second winding portion 42. The outer coil diameter r4 of the second winding portion 42 is smaller than the inner coil diameter r3 of the first winding portion 41. When the helical spring 1A is compressed, the second winding portion 42 can enter the inner side of the first winding portion 41, such as... Figure 11 The two dots are shown by the line Z1.

[0090] Regarding structures and functions other than those described above, since the helical spring 1A of the second embodiment is the same as the helical spring 1 of the first embodiment, it is given the same reference numerals and the description is omitted.

[0091] Industrial availability

[0092] The helical spring of the present invention can be applied to helical springs used in various devices, including vehicle suspension systems.

Claims

1. A coil spring, the coil spring composed of a wire (2) having one end and the other end, having a first seat coil (11) including the one end of the wire (2), a second seat coil (12) including the other end of the wire (2), an effective portion (13) having a plurality of winding portions (13a) formed between the first seat coil (11) and the second seat coil (12), and a gap (Gl) between the winding portions (13a) adjacent to each other, the wire (2) having, a circular cross-sectional portion (30) having a first cross-sectional surface (SI) at right angles to a length direction of the wire (2) being circular, a square cross-sectional portion (31) having a length from the one end of the wire (2) exceeding the first seat coil (11), a second cross-sectional surface (S2) at right angles to the length direction being substantially square, and a side length of the second cross-sectional surface (S2) being less than or equal to one half of a square root of a diameter of the wire (2) of the circular cross-sectional portion (30), and the second cross-sectional surface (S2) being constant in the length direction, a tapered portion (32) having 1.0 or more turns between the circular cross-sectional portion (30) and the square cross-sectional portion (31), a third cross-sectional surface (S3) at right angles to the length direction changing from circular to substantially square and decreasing in cross-sectional area from the circular cross-sectional portion (30) toward the square cross-sectional portion (31).

2. The coil spring according to claim 1, the square cross-sectional portion (31) including a first face (31a) and a second face (31b) on an outer side and an inner side of a central axis (Cl) of the coil spring, and a third face (31c) and a fourth face (31d) at right angles to and parallel to each other of the first face (31a) and the second face (31b).

3. The coil spring according to claim 2, the square cross-sectional portion (31) having at least a first winding portion (41) and a second winding portion (42), and in a state where the coil spring is compressed, a contact portion (43) where the third face (31c) of the first winding portion (41) and the fourth face (31d) of the second winding portion (42) contact each other.

4. The coil spring according to claim 2, the tapered portion (32) having a first flat portion (32a) connected to the first face (31a) of the square cross-sectional portion (31), a second flat portion (32b) connected to the second face (31b), a third flat portion (32c) connected to the third face (31c), a fourth flat portion (32d) connected to the fourth face (31d), a first arc portion (32e) between the first flat portion (32a) and the third flat portion (32c), a 2nd arcuate portion (32f) between the 1st planar portion (32a) and the 4th planar portion (32d), a 3rd arcuate portion (32g) between the 2nd planar portion (32b) and the 3rd planar portion (32c), a 4th arcuate portion (32h) between the 2nd planar portion (32b) and the 4th planar portion (32d).

5. The coil spring according to claim 1, wherein a cross section of the wire (2) of the 2nd seat winding portion (12) is circular, and a diameter of the wire (2) of the 2nd seat winding portion (12) is the same as a diameter of the wire (2) of the circular cross section portion (30).

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