JP2019069710A - Leaf suspension device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leaf suspension device capable of improving durability as compared with the conventional case without causing deterioration of ride quality. SOLUTION: Regarding a leaf suspension device in which a plurality of leaf springs 2A and 2B are laminated and their respective intermediate portions in the longitudinal direction are mutually fixed, the plate thickness of the first-stage leaf spring 2A from the top is the portion forward from the intermediate portion. Is relatively increased relative to the rear part to form an asymmetrical shape, and for the second stage leaf spring 2B, the plate thickness of the rear part from the middle part is relatively reduced with respect to the front part, and the entire leaf springs 2A and 2B are formed. The front and rear spring constants are configured to be the same. [Selection diagram] Fig. 1

Description

  The present invention relates to a leaf suspension device.

  There are various types of suspensions used to suspend vehicle axles to the side rails. Among them, a leaf suspension device formed by laminating a plurality of leaf springs has a simple structure. It is characterized by low cost, high strength and high durability, and has been widely used in vehicles such as trucks.

  FIG. 5 shows an example of a conventional leaf suspension apparatus formed by laminating a plurality of leaf springs. In FIG. 5, 1 denotes a pair of left and right side rails 2A which extend in the longitudinal direction of the vehicle and form a part of a chassis frame. , 2B show leaf springs installed in the longitudinal direction of the vehicle in two layers along the side rails 1, and the leaf springs 2A, 2B have plate thickness in the middle so that they have equal stress in the longitudinal direction. It is thick and has a tapered shape which becomes thinner toward the front and rear end portions, and the respective longitudinal middle portions are fixed to each other by the center bolt 3 and the axle 5 is coupled to the lower surface of the middle portions via the U bolt 4 It is supposed to be

  Here, the front end portion of the first stage leaf spring 2A from the top is wound upward to form an eye 2x, which can be tilted relative to the horizontal pin 7 mounted on the front bracket 6 on the side rail 1 side. On the other hand, the rear end of the first stage leaf spring 2A is wound upward similarly to the front end to form an eye 2y, and the eye 2y is used as a rear bracket on the side rail 1 side. The shackle 9 is mounted on the horizontal pin 10 of the shackle 9 so as to be able to tilt freely, and expansion and contraction in the front-rear direction due to bending of the leaf springs 2A and 2B is absorbed by the swing of the shackle 9 It has become so.

  In addition, there exist following patent document 1 grade | etc., As a prior art literature information relevant to this invention.

Unexamined-Japanese-Patent No. 2003-267019

  However, in the conventional leaf suspension device as described above, when the reduction of the spring constant is advanced to improve the riding comfort, the first stage leaf spring 2A is generated due to the rotational moment around the axis at the time of driving or braking. For example, as shown by a two-dot chain line in FIG. 5, a large driving torque is applied at the time of start, so that the front part curves upward from the middle part of the first stage leaf spring 2A. S-shaped deformation is likely to occur in which the rear part is curved downward from the middle part, but local stress may be applied to the front part of the first leaf spring 2A curved upward to cause premature breakage. I was sorry.

  That is, since the leaf springs 2A and 2B originally form the initial state of the bow shape which is entirely curved downward, they are set so as to be flatly deformed and approach the horizontal state in the constant storage state. When 2A and 2B are in the upward curved state opposite to the initial state, a large local stress is generated in the front portion curved upward by the first stage leaf spring 2A whose front end is restrained to the side rail 1 side. If this happens, breakage may occur in this upward curved front part, and if the front part of the first stage leaf spring 2A is broken, the positioning function of the axle 5 is impaired and the vehicle can not travel. There is also concern that

  The second stage leaf spring 2B is only along the lower surface of the first stage leaf spring 2A, and there is no restriction on the side rail 1 side of the front and rear end portions, so local stress that causes breakage occurs. There is no concern that the rotational moment around the axis generated in the axle 5 is mainly borne by the leaf spring 2A of the first stage.

  However, in the case of the example illustrated here, an eye 2x 'surrounding the horizontal pin 7 in a distant winding is formed at the front end of the second stage leaf spring 2B from the top. Even if the front part of 2A is broken, the eye 2x 'at the front end of the second stage leaf spring 2B is prevented from being caught by the horizontal pin 7 and the entire leaf springs 2A and 2B falling off. It is

  Further, in the illustration of the two-dot chain line in FIG. 5, the case where a large driving torque is applied at the time of start is illustrated, but as shown by the one-dot chain line in FIG. In the opposite direction, an S-shaped deformation occurs in which the front part curves downward from the middle part of the leaf springs 2A and 2B and the rear part curves upward from the middle part. There is a risk of breakage at the rear part of the

  For this reason, it is a fact that measures have been taken to suppress windup deformation by increasing the thickness of the first stage leaf spring 2A having a fear of breakage as a countermeasure in the related art, but the first stage leaf When the plate thickness of the spring 2A is increased, the spring constant of the entire leaf springs 2A and 2B is increased, and there is a problem that the ride comfort is deteriorated.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a leaf suspension device capable of improving the durability without causing the deterioration of the riding comfort.

  The present invention is a leaf suspension apparatus in which a plurality of leaf springs are stacked and their respective longitudinal middle portions are fixed to each other, and a front portion and a rear portion sandwiching the middle portion of the first leaf spring from the top Among them, the plate thickness on the side where the local stress is to be reduced is relatively increased to form front and rear asymmetry, and the leaf spring on the second and subsequent stages from the top is the side on which the plate thickness is relatively increased by the first stage leaf spring It is characterized in that the plate thickness is relatively reduced so that the front and back spring constants of the whole leaf spring are equal.

  In this way, among the front and rear portions of the first stage leaf spring from the top, the plate thickness on the side where the local stress is to be reduced is relatively increased to suppress the amount of deformation, thereby the portion In the second stage leaf springs from the top, it is possible to reduce the plate thickness relatively by increasing the plate thickness relatively with the first stage leaf spring to reduce deformation. By controlling the amount of deformation of the first stage leaf spring by increasing the amount, it is possible to keep the spring constant of the whole leaf spring equal before and after, thereby suppressing the increase of the spring constant of the whole leaf spring. It is possible to avoid local early breakage in advance.

  In order to more specifically practice the present invention, the thickness of the front portion of the first stage leaf spring is increased relative to the rear portion, and the thickness of the front portion of the second and subsequent leaf springs is set to the rear To reduce relative to the part so that the spring constant of the whole leaf spring becomes equal, or to increase the thickness of the rear part of the first stage leaf spring relative to the front part, It is possible to reduce the thickness of the rear portion of the leaf spring after the step relative to the front portion so that the spring constant of the entire leaf spring becomes equal.

  According to the above-described leaf suspension device of the present invention, the following various excellent effects can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the thickness of the front side and the rear side of the first stage leaf spring from the top is relatively increased by decreasing the local stress, and the amount of deformation is increased. Even if it is suppressed, the amount of suppression of deformation in the first stage leaf spring can be adjusted by the second and subsequent leaf springs, and the front and rear spring constants of the entire leaf spring can be kept equal. A local early breakage can be avoided in advance while suppressing an increase in the spring constant, and the durability can be improved as compared to the conventional art without causing a deterioration in the ride comfort.

  (II) According to the invention described in claim 2 of the present invention, when local stress in the front portion of the first stage leaf spring causes a problem, local premature breakage of the front portion is avoided in advance. The present invention can be effectively applied to vehicles in which windup deformation at the time of start-up is regarded as a particular problem.

  (III) According to the invention described in claim 3 of the present invention, when local stress in the rear portion of the first stage leaf spring causes a problem, local premature breakage of the rear portion can be avoided in advance. It can be effectively applied to vehicles in which windup deformation during braking is regarded as a particular problem.

It is a side view of the constant storage state which shows an example of the form which implements this invention. It is a side view which shows the example of FIG. 1 in the state of the windup deformation at the time of start-up. It is a side view of a constant volume state shown about another embodiment of the present invention. FIG. 4 is a side view showing the example of FIG. 3 in a windup deformation state at the time of braking. It is a side view which shows a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show an example of the embodiment for implementing the leaf suspension device of the present invention, and the portions given the same reference numerals as in FIG. 5 represent the same things, and the conventional example described above in FIG. In the same manner, the front bracket 6 and the rear bracket 8 are disposed at the front and rear positions sandwiching the axle 5 of the side rail 1, the two leaf springs 2A and 2B are stacked, and the longitudinal middle portions are They are fixed to each other by bolts 3, and the front end of the first leaf spring 2A from the top is pivotally attached to the front bracket 6, and the rear end is pivotally attached to the rear bracket 8 via a shackle 9 swingable back and forth. The axle 5 is suspended via a U-bolt 4 at an intermediate portion of the leaf springs 2A and 2B, but the front portion of the leaf spring 2A at the first stage from the upper side than the intermediate portion Plate thickness is relatively increased with respect to the rear portion to form front and rear asymmetry, and for the second stage leaf spring 2B, the plate thickness of the rear portion with respect to the middle portion is reduced relative to the front portion to form leaf spring 2A, It is characterized in that it is configured such that the front and rear spring constants of the entire 2B are equal.

  That is, the example shown in FIG. 1 and FIG. 2 shows the case where windup deformation (see FIG. 2) at the time of start-up is applied to a vehicle particularly regarded as a problem. In the case of a high-power running vehicle, there is a concern that wind-up deformation may become large due to the rotational moment around the axis generated on the axle 5 at the start of the vehicle and the vertical stroke due to the unevenness of the road. There is less friction on the road surface, so windup deformation does not increase. However, in such a vehicle, local stress acts on the front part of the first stage leaf spring 2A from the middle part of the first stage leaf spring and it is easily broken. Therefore, the thickness of the front portion of the first stage leaf spring 2A is paired with that of the rear portion in order to reliably avoid a situation where the positioning function of the axle 5 is impaired. So that relatively increase.

  However, simply increasing the plate thickness of the front part of the leaf spring 2A relative to the rear part raises the overall spring constant and makes the ride worse, so the second stage leaf spring 2B from the top The reduction of the amount of deformation in the first stage leaf spring 2A is adjusted by relatively reducing the thickness of the side where the thickness is relatively increased by the first stage leaf spring 2A and increasing the amount of deformation, The conventional ride comfort is secured by making the spring constant equal on the front and back.

  Thus, in this way, the thickness of the front portion of the first stage leaf spring 2A from the top is increased relative to the rear portion to suppress the amount of deformation, thereby reducing the stress value in that portion In the first stage leaf spring 2A, the plate thickness of the rear portion from the middle portion is reduced relative to the front portion by the second stage leaf spring 2B from the top to increase the deformation amount. Since it is possible to adjust the amount of suppression of deformation and keep the front and back spring constants of the entire leaf springs 2A and 2B equal, local early breakage while suppressing the increase of the spring constants of the entire leaf springs 2A and 2B. Can be avoided in advance.

  Therefore, according to the above embodiment, even if the thickness of the front portion of the first stage leaf spring 2A is increased relative to the rear portion to suppress the amount of deformation, the deformation of the first stage leaf spring 2A Since the amount of suppression can be adjusted by the second and subsequent leaf springs 2B and the spring constants of the entire leaf springs 2A and 2B can be kept equal, the increase in the spring constants of the entire leaf springs 2A and 2B can be suppressed. However, local early breakage can be avoided in advance, and durability can be improved as compared to the conventional one without causing deterioration in ride comfort.

  Further, although the above description is directed to a case where windup deformation at start is considered to be a particular problem, in the example shown in FIGS. 3 and 4, windup deformation at braking ( Fig. 4) shows a case where the present invention is applied to a vehicle that is particularly regarded as a problem, for example, when braking for a vehicle intended to travel at high speed with a large load load on a paved road with high friction on the road surface. Wind-up deformation is a particular problem, and local stress acts on the rear part of the first stage leaf spring 2A from the middle part to make it easy to break, so the positioning function of the axle 5 is impaired. To make the plate thickness of the rear part of the first stage leaf spring 2A relatively to the front part to form a front-back asymmetry, and the second stage leaf spring May be configured to spring leaves 2A the thickness of the rear portion from the middle portion to reduce relatively with respect to the front portion, the front and rear of the spring constant of the whole 2B becomes equal for 2B.

  The leaf suspension device of the present invention is not limited to the above-described embodiment, and in the illustrated example, a two-layered leaf spring is described, but a type in which three or more leaf springs are stacked is used. In this case, it is necessary to relatively reduce the plate thickness on the side where the plate thickness is relatively increased by the leaf spring of the first stage with the leaf springs of the second stage from the top to increase the deformation amount In the first stage leaf spring, the amount of suppression of deformation is adjusted so that the spring constant as a whole is equal before and after, and various changes can be made without departing from the scope of the present invention. Of course.

2A leaf spring 2B leaf spring

Claims (3)

  A leaf suspension device in which a plurality of leaf springs are stacked and respective longitudinal middle portions are fixed to each other, wherein local stress is applied to the front portion and the rear portion across the middle portion of the first leaf spring from the top The plate thickness on the side where it is desired to reduce is relatively increased to form an anteroposterior asymmetry, and for the leaf springs in the second and subsequent stages from the top, the plate thickness on the side on which the plate thickness is relatively increased by the first stage leaf spring is relative A leaf suspension device characterized in that the front and rear spring constants of the entire leaf spring are equal to each other.   The thickness of the front portion of the first stage leaf spring is increased relative to the rear portion, and the thickness of the front portion of the second and subsequent leaf springs is decreased relative to the rear portion to reduce the thickness of the entire leaf spring. The leaf suspension device according to claim 1, wherein the spring constant is configured to be equal.   The thickness of the rear portion of the first stage leaf spring is increased relative to the front portion, and the thickness of the rear portion of the second and subsequent leaf springs is decreased relative to the front portion to obtain front and rear leaf springs. The leaf suspension device according to claim 1, wherein the spring constant is configured to be equal.

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