JP2005226673A - Coil spring and suspension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil spring having a load axis offset with respect to a geometric center axis and a vehicle suspension system using such a coil spring.
A coil spring is wound so that a winding diameter is larger in an intermediate portion than an end portion in the axial direction, and at one side position, the outline of the coil is aligned substantially in a straight line in the axial direction. On the other hand, at the other side position 9, the outline of the coil bulges outward to form a convex shape. That is, the coil outline forms a D shape when viewed from a specific side direction. This realizes a coil spring having a load axis that is offset in parallel to the axis without receiving a buckling displacement.
[Selection] Figure 1

Description

  The present invention relates to a coil spring having a load axis that is offset with respect to a geometric central axis, and a vehicle suspension system using such a coil spring.

  2. Description of the Related Art Conventionally, for example, in a strut type suspension device used in an automobile or the like, a cylindrical shock absorber having a cylinder filled with oil and a piston received therein, and a compression provided to surround the cylinder type shock absorber There is an assembly in which an assembly including a coil spring is assembled so as to connect a vehicle body and a wheel carrier. However, since the input from the tire does not necessarily coincide with the axis of the shock absorber and is accompanied by a lateral load, a lateral load and a moment act on the sliding portion between the cylinder and piston of the shock absorber, resulting in a sliding resistance. As a result, the ride comfort of the car is impaired and the life of the shock absorber is shortened.

  In view of this, conventionally, the coil spring is offset to the axis of the shock absorber, and the lateral load and moment generated in the sliding portion between the shock absorber cylinder and the piston due to the lateral load and moment generated by the coil spring are reduced. Methods for reducing the moment are known. However, the offset amount is limited by the diameter of the coil spring, the installation space, and the like, and the lateral load and moment sufficient to completely cancel the lateral load and moment received by the input from the tire cannot be generated.

  Japanese Laid-Open Patent Publication No. 1-156119 proposes to reduce a lateral load and a moment generated in a sliding portion between a cylinder and a piston of a shock absorber by using a coil spring whose axis is curved in a free state. Has been. However, it is not clear how a bending coil spring can be held in the straightened state, and a bending coil spring suitable for a wheel suspension cannot be manufactured at low cost. In addition, since such a coil spring is subjected to a large buckling displacement during use, it has been practically impossible to apply to a use with a limited installation space, particularly a wheel suspension device.

  In view of this, Japanese Patent Laid-Open No. 2000-562229 by the same applicant proposed a coil spring having a load axis inclined with respect to the axis and a wheel suspension using such a coil spring. Accordingly, the load axis can be inclined with respect to the axis with almost no buckling displacement, and the lateral load and moment generated in the sliding portion between the cylinder and the piston of the shock absorber can be reduced. According to the research by the inventor thereafter, if the distribution of the coil diameter is appropriately determined, a coil spring having a load axis offset in parallel to its axis cannot be realized without receiving a buckling displacement. I got the knowledge. In particular, it has been found that if a coil spring having a load axis that is inclined with respect to the axis of the coil spring and that is offset in parallel can be realized, the lateral load and moment can be reduced more suitably.

  In view of the problems of the prior art and the inventor's knowledge, the main object of the present invention is to have a load axis that is offset substantially parallel to the mounting axis or the geometric axis, and that is An object of the present invention is to provide a coil spring that is not subjected to bending displacement.

  A second object of the present invention is to provide a vehicle suspension device using such a coil spring.

  According to the present invention, such an object is a coil spring wound such that a winding diameter is larger in an intermediate portion than in an end portion with respect to the axial direction, and the projection is orthogonal to the axial direction. When viewed on a plane, the coil wires are aligned with each other on one side over their entire length (ie, the line connecting the outer diameters of the coil springs is substantially parallel to the central axis of the coil) A coil spring (hereinafter referred to as a “D-type compression coil spring”) characterized in that a coil wire in the middle portion of the coil spring extends outward most on the other side facing the one side. Achieved by providing.

  Moreover, according to this invention, the suspension apparatus for vehicles using such a compression coil spring is provided.

  By doing so, the attachment axis or the geometric axis and the load axis can be offset substantially in parallel. Therefore, when such a coil spring is used, in the vehicle suspension system or the like, the problem caused by the fact that the axis of attachment of the coil spring does not coincide with the axis of the load applied to the coil can be solved. In particular, if such a coil spring is used in a strut type vehicle suspension system, the lateral force acting between the piston and cylinder of the shock absorber is minimized, so The sliding resistance due to the generated lateral force can be suitably reduced, the riding comfort of the vehicle can be improved, and the durability of the shock absorber can be improved.

  Further, since the coil wire is wound so that the winding diameter gradually increases from the end portion to the intermediate portion, it is possible to avoid a sudden change in the winding diameter between adjacent windings. If the winding diameter changes abruptly, buckling displacement is likely to occur, and the application of the coil spring is limited. Furthermore, the intermediate portion does not need to be positioned at the midpoint in the axial direction, and the intermediate portion may be biased upward or downward with respect to the midpoint in the axial direction in accordance with a request for a mounting space.

  Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

  Figures 2a and 2b show a compression coil spring 2 with a conventional type of end turn. Generally, it is formed by winding the coil wire 4 around the central axis 5, but since the number of turns is finite and not completely symmetric around the central axis 5, the load axis 6 is slightly relative to the central axis 5. Inclined. The load axis 6 can be considered as the direction of the reaction force generated in the spring 2 when a load is applied in the direction of the center axis 5.

  1a and 1b show a D-type compression coil spring 1 according to the invention. One side position 8 is set as a reference position for changing the winding diameter, and a straight line 8 'connecting the one side position 8 is substantially parallel to the central axis (attachment axis connecting the central positions of both seating surfaces) 5. Yes. Furthermore, the winding diameter of the coil wire 3 is sequentially increased from each end in the axial direction of the D-type compression coil spring 1 to an intermediate position in the axial direction. Accordingly, at the other side position 9 opposite to the one side position 8, the coil wire 3 is located along a curved line 9 'that protrudes outward most from the central axis 5 and has an outwardly convex shape. It will be.

  FIG. 3 is a graph showing the winding diameter of the coil wire with respect to the axial position of the compression coil springs 1 and 2 in terms of the number of turns. In the conventional compression coil spring 2, the winding diameter is small at the end winding portion, but the winding diameter is constant at the remaining portion. In the D-type compression coil spring 2, the winding diameter of the coil wire 3 is sequentially increased from each end in the axial direction to an intermediate position in the axial direction. Also, as shown in FIG. 1a, when viewed from the direction perpendicular to the plane connecting the one side position 8 and the other side position 9, the coil outline is Are aligned in a straight line in the axial direction, while the other side position 9 bulges so that the contour of the coil is convex outward. That is, the coil outline is D-shaped when viewed from a specific side direction.

In the D-type compression coil spring 1, since a large portion of the coil wire 3 is biased toward the other side position 9 with respect to the axial direction connecting the center positions of the seating surfaces, It is considered that the resultant force of the reaction force generated at each point of the coil wire 3 is offset from the central axis in the direction of the other side position 9. That is, the load axis 6 of the conventional compression coil spring is displaced to the position indicated by the load axis 7 in the D-type compression coil spring 1. The D-type compression coil spring can be manufactured by various methods.
(1) In a state where one side position 8 of a normal coil spring is constrained by a jig, using a pig tailor for forming the end winding portion, each end of the coil wire is gripped and tightened. Finish to the desired shape.
(2) Using a coiling machine, a barrel-shaped coil spring is formed, bent and deformed, and finished in a desired shape.
(3) Using a mandrel that can be expanded and contracted, the coil wire is wound around a mandrel that has been expanded cold or hot, and after finishing to a desired shape, the mandrel is contracted and pulled out of the coil.
(4) Finish in a desired shape by cold forming using pins or rolls.

  In such a coil spring, it is desirable to minimize the amount of buckling deformation at the same time that the attachment axis of the coil spring and the load axis are offset from each other. This is because the coil spring is often installed at a position where the installation space is limited. In the case of a curved coil spring based on the prior art, the bending of the coil spring increases as it is compressed and deformed. In the case of the D-type compression coil spring, the coil wire does not protrude in any direction even if it is compressed and deformed.

  4 and 5 show the state when the D-shaped coil spring and the curved coil spring are compressed and deformed, and the amount of overhang of the coil wire is indicated by ΔR. FIG. 6 is a graph showing the extension amount ΔR of the coil wire with respect to the load axis offset amount achieved for these two types of springs. In the case of a curved coil spring, an attempt is made to increase the load axis offset amount. The wire extension amount ΔR also increases, and the installation space is limited. On the other hand, with the D-type compression coil spring, even if the load axis offset amount is increased, the coil wire hardly protrudes outward. It can be seen that there is no space restriction.

  FIG. 7 is a partially cutaway front view schematically showing the main part of the vehicle suspension device to which the present invention is applied. The tire 19 is attached to the wheel carrier 12, the lower end of the wheel carrier 12 is swingably attached to the lower part of the vehicle body 11 via the link member 13, and the upper end of the wheel carrier 12 is attached to the upper part of the vehicle body via the strut assembly 14. It is pivotally attached. The strut assembly 14 includes a shock absorber 15 formed of a cylindrical oil damper, and a compression coil spring 16 held by spring seats 17 and 18 between a cylinder of the shock absorber 15 and an upper end of a piston rod. The upper spring seat 17 is pivotally attached to the vehicle body 11 via a rubber bushing or the like together with the upper end of the piston rod of the shock absorber 15, and the lower spring seat 18 is integrally coupled to the outer periphery of the cylinder of the shock absorber 15. Has been.

  Here, the central axis 21 of the compression coil spring 16 does not coincide with the load axis 22 as the road surface reaction force acting between the road surface and the vehicle body. This is because the road surface reaction force 22 from the road surface side is received from the tire 19 spaced outward from the wheel carrier 12, whereas the compression coil spring 16 must be attached to the wheel carrier 12. Therefore, when a normal compression coil spring is used, a lateral load and a moment act on the sliding portion between the cylinder and piston of the shock absorber, causing various problems. However, if the D-type compression coil spring according to the present invention is used, the load axis can be offset in parallel to the central axis as indicated by reference numeral 23, and the occurrence of such a lateral load and moment is minimized. can do.

  In particular, the length along the strand of the spring at a certain winding direction angular position for each winding along the vertical axis as proposed in Japanese Patent Application Laid-Open No. 2000-562229 by the same applicant. Coil springs wound so that the pitch angle given as the amount of change in the height of the corresponding point on the strand with respect to the variation of the length becomes the maximum and the minimum only once over the entire length of the coil, By holding it so that it can expand and contract in the vertical axis direction, the characteristics of the D-type compression coil spring can be combined with the compression coil spring that is adapted to generate a lateral force between the two ends as it expands and contracts. For example, the offset amount and the inclination amount of the load axis can be controlled independently, and the occurrence of a lateral load and a moment can be minimized in every scene.

  Although the preferred embodiment of the present invention has been described above, those skilled in the art will be able to make various modifications without departing from the scope of the present invention.

It consists of a and b, a is a side view of D type compression coil spring based on this invention, b is the bottom view. It consists of a and b, a is a side view of the normal compression coil spring based on a prior art, and b is the bottom view. It is a graph which shows distribution of the winding diameter of the normal compression coil spring based on the prior art of the D type compression coil spring based on this invention. It is a side view which shows a mode that the compression deformation of the D-type compression coil spring based on this invention is received. It is a side view which shows a mode that the bending compression coil spring based on a prior art receives a compression deformation. 6 is a graph showing the amount of lateral extension of the coil with respect to the amount of offset of the lateral load axis achieved with the compression deformation of the compression coil spring shown in FIGS. It is a typical front view showing a wheel suspension device to which a D type compression coil spring based on the present invention was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 D type compression coil spring 2 Conventional compression coil spring 3, 4 Coil wire 5 Center axis 6, 7 Load axis 8 One side position 9 Other side position 11 Car body 12 Wheel carrier 13 Link member 14 Strut assembly 15 Shock absorber 16 Compression coil springs 17 and 18 Spring seat 19 Tire 21 Center axis 22 Load axis 23 (for road reaction force) Load axis (for D-shaped coil spring)

Claims (4)

A coil spring wound in such a manner that the winding diameter is larger in the middle portion than in the end portion in the axial direction;
When viewed on the projection plane orthogonal to the axial direction, the coil wires are aligned with each other on one side and over the entire length, on the other side facing the one side, A coil spring characterized in that a coil wire at an intermediate portion of the coil spring extends outward most. The coil spring according to claim 1, wherein the coil wire is wound so that a winding diameter gradually increases from the end portion to the intermediate portion. A suspension system for a vehicle having a cylindrical shock absorber and a compression coil spring surrounding the shock absorber between a vehicle body and a wheel,
The compression coil spring is wound so that its winding diameter is larger in the middle than in the end in the axial direction, and when viewed on a projection plane orthogonal to the axial direction, the coil The wires are aligned with each other on one side over almost the entire length, and the coil wire in the middle portion of the coil spring extends outward most on the other side facing the one side. A vehicle suspension system characterized by the above. The suspension system for a vehicle according to claim 4, wherein the coil wire is wound so that a winding diameter gradually increases from the end portion to the intermediate portion.

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