JPS623282Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tandem suspension system used for heavy-load trucks and the like.

BACKGROUND OF THE INVENTION Tandem suspension systems have been used for many years on heavy-duty trucks that are used only on the road or on heavy-duty trucks that are used off-road. This suspension system is equipped with equalization means that distribute the load evenly over the axle and reduce the effects of bumps and irregularities on the road surface, according to the "lever" principle. Torque rods help absorb torque. Torque here is the force that causes the axle to rotate its neutral shaft forward or backward due to driving force or braking force.
The ends of the equalizing beams are usually provided with resilient supports, such as rubber bushings, which connect them to the axle bracket. A central bushing is also provided in the central portion of each equalizing beam to connect a spring saddle or frame bracket to each beam. If these bushings are used, there is no need to attach lubricating parts to these locations.

A central bushing for mounting the equalizing beam for movement relative to a spring saddle or frame bracket has an inner sleeve and an outer sleeve. An elastomer insert is provided between these sleeves to provide a damping effect between the equalizing beam and the frame bracket when the road surface that the tandem wheels encounter is uneven. In this way, when one of the wheels encounters a bump or hole in the road surface and is located at a different height than the other wheel, the elastomeric insert is subjected to torsional loads. The elastomeric insert is also subjected to shear stresses when the sleeves move in opposite directions, such as when the vehicle turns. Furthermore, under certain conditions, such as when the vehicle is turning, a conical deflection occurs in the beam center bushing. Conical deflection refers to a phenomenon in which the axes of the inner and outer sleeves are no longer aligned with each other and follow conical trajectories. During such movements, the sliding movement between the metal sleeve and the elastomeric insert is minimized so that heat generation occurs within the elastomeric insert rather than at the interface between the sleeve and the elastomeric insert. I can do it. Continuous excessive relative movement between the sleeve and the elastomeric insert will cause friction, wear, and failure of the pair.

Problems with the Prior Art An improvement in the durability of beam center bushings is described in U.S. Pat. No. 3,666,335 to Arthur Mundy. This patent includes a wear-resistant sleeve at the end of the elastomeric insert between a pair of rigid sleeves coaxially and spaced apart from each other, one inside the other. It is provided so as to be in contact with one of the two, and usually to be separated from the other rigid sleeve. One drawback of this device is that the elastomer insert does not occupy all of the available space between the rigid sleeves. Therefore, the contact area between the metal and the elastomeric insert is reduced, which increases the radial stress applied to the elastomer insert. Furthermore, since the wear-resistant sleeve is stiffer than the elastomeric insert, the radial or conical damping effect is reduced, defeating one of the purposes of the bushing, and the rigid sleeve and semi-rigid wear-resistant bushing The shock effect is caused by the sudden contact with the

Tandem suspension systems for trucks are sometimes subjected to conditions that impose a conical load on the central bushing of the beam. When this conical load is repeatedly applied, the bushing flexes and the elastomeric insert is released from compression at its axial end. The elastomer insert therefore begins to wear out and
The degree of compression becomes smaller and smaller. Repeated wear and reduced compression cause failure of the elastomeric member.

SUMMARY OF THE INVENTION In order to overcome the problems of the prior art mentioned above, it is an object of the present invention to provide a tandem suspension system having a central bushing configured to rapidly reduce the movement of the elastomeric insert of the bushing relative to the inner and outer sleeves. Our goal is to provide the following.

[Means for Solving the Problems] As shown in FIGS. 1 to 5 showing embodiments of the present invention, the tandem suspension system of the present invention has a pair of parallel equalizing beams 11, 12, support means for supporting the ends of each equalizing beam 11, 12, and end brackets 15, 16 mounted on a pair of isolated parallel transverse axles connected to each support means. , a central bushing 19 located in the center of each equalizing beam 11,12, and frame bracket means connected to the equalizing beams 11,12 by the central bushing 19. Each central bushing 19 has an inner cylindrical sleeve 24, an outer cylindrical sleeve 30, and a cylindrical elastomer insert 31 inserted between and bonded to both sleeves.
It consists of In the present invention, the elastomer insert 31 is exposed in the axial direction from both sides of the space, with the first part occupying almost the entire space between the two cylindrical sleeves and being in a radially compressed state. and a second portion having an annular end that extends in the same direction and is unrestricted in the axial and radial directions under any load condition.

[Operation of the invention] In the tandem suspension system of the invention, the elastomer insert 31 is placed in a compressed state, and the surface of the elastomer insert 31 is adhesively bonded to the surface of each sleeve 24, 30, so that a compressive force acts. No wear occurs when not in use. Since loss of elastomer material due to wear etc. is thus avoided, the durability of the bushing is significantly improved. The contact area between the elastomeric insert 31 and the sleeves 24, 30 is maintained at a maximum. More specifically, the present invention includes an inner sleeve 24 and an outer sleeve 30.
It includes a tandem suspension having a central bushing 19 including a central bushing 19.

According to one embodiment of the invention, a cylindrical elastomeric insert 31 is arranged between the two sleeves 24, 30 and adhesively bonded thereto. One or both of the outer and inner sleeves 24, 30 are deformed by forging, such as swaging, to compress the elastomeric insert 31.

According to another embodiment of the invention, the elastomeric insert 31 has a thickness greater than the space between the inner and outer sleeves 24, 30. A heat-activated adhesive is applied to the inner surface of the outer sleeve 30 and the outer surface of the inner sleeve 24, and the elastomeric insert 31 is pushed between each sleeve, activating the adhesive and attaching the elastomeric insert 31 to the sleeve. is glued to. The elastomer insert 31 is approximately 45% to 55% thicker than its uncompressed thickness.
It is desirable that it be compressed to a thickness of . In many applications, it is desirable that the axial length of the elastomeric insert 31 be greater than or equal to twelve times its thickness.

[Example] An example of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a tandem suspension system 10 is shown which is particularly suitable for heavy duty trucks and the like. Tandem suspension 10 has a pair of equalizing beams 11 and 12. Each equalized beam 11 and 1
Bushings 13 and 14 are supported at the ends of 2. The ends of each bushing 13 and 14 are connected by end brackets 15 and 16 to a pair of spaced parallel transverse axles 17 and 18. A central bushing 19 is provided in the center of each of the equalizing beams 11 and 12. Each central bushing 19 is connected to a spring saddle 20 in a manner that will be clear from the description below.
Each of the spring saddles 20 carries a leaf spring 21. Each leaf spring 21 is provided with a spring hanger 22 which supports the body of the truck. In the illustrated example,
Although leaf springs 21 are used, other types of spring means for supporting the truck body may be used, such as air bags, rubber shears, or rubber pads. A torque rod 23 is provided to prevent rotation of the vehicle due to driving or braking forces. To explain the central bushings 19 in more detail, each central bushing 19 has a cylindrical sleeve 24 inside. sleeve 24
has an end plate 25 provided so as to close one end thereof. A transverse tube 34 (FIG. 1) is housed in a sleeve inside the central bushing 19 and connects the equalization beams 11 and 12. The ends of the inner sleeve 24 are attached to each other in openings 28 and 29 provided in the suspension legs 28 and 29 of each spring saddle 20 in mutual alignment. Each central bushing 19 also includes a tubular or cylindrical elastomeric insert 31 disposed between the outer cylindrical sleeve 30 and the inner sleeve 24.

Elastomeric insert 31 is stressed by movement of inner and outer sleeves 24 and 30 and the parts connected thereto. An example of a phenomenon that usually occurs is as shown in Figures 3 and 4.
This is a phenomenon in which the imaginary planes 32 and 33 perpendicular to the inner and outer sleeves 24 and 30 are no longer aligned with each other and a conical stress is applied. Such a misalignment can occur when the vehicle encounters a bump in the road surface, as shown in FIG. It happens sometimes. Greater cone stresses occur when the vehicle turns.

The durability of the bushing of the present invention is such that the elastomeric insert 31 is connected to the inner and outer sleeves 24 and 30.
This is a significant improvement over the conventional method. According to one embodiment of the invention, the elastomeric insert 31 is forged into the outer sleeve 30.
The inner sleeve 24 is compressed by either radially inwardly deforming the inner sleeve 24 or expanding the inner sleeve 24 radially outwardly, or both.

The bushing of this aspect of the invention is manufactured by applying adhesive to the outer surface of the inner sleeve 24. Both sleeves 24, 30 are placed in a mold and rubber is injected between the sleeves. A bond can be obtained by curing the injected rubber. During curing, the rubber expands and bonds to the surface of the sleeve when heated. When cooled, shrinkage occurs, but the bond prevents the rubber from shrinking, creating tensile stress within the rubber. In order to eliminate tensile stresses and create compressive stresses within the rubber, the outer sleeve 30 is swaged to radially contract or the inner sleeve 24 is radially expanded. Accordingly, depending on the final desired dimensions, the dimensions of the outer sleeve 30 may be increased or the dimensions of the inner sleeve 24 may be reduced. Furthermore, if the conical stress is large, it is desirable that the axial length of the elastomer insert be at least 12 times its thickness. Elastomer insert 3
The annular axial end of 1 protrudes from the space between the inner and outer sleeves 24 and 30 and is exposed to the outside of this space. As shown in FIGS. 2, 3 and 4, these ends are not limited axially by legs 28 and 29 and radially by an outer sleeve 30. do not have.

These annular ends, which thus constitute the second part of the elastomeric insert 31, are connected to the sleeve 24.
and 30 in a radially compressed state. As shown in FIGS. 3 and 4, when sleeves 24 and 30 are no longer in a coaxial relationship and a conical stress is applied to elastomeric insert 31, the gap on one side of the space will widen. At this time, if there is no annular end portion extending in the axial direction as in the present invention, a large tensile stress will occur at the joint between the sleeves 24 and 30 and the elastomer insert 31 on the side where the gap has widened. As a result, the joint between the two will be destroyed, and in the worst case, the central bushing 19 will break. However, in the present invention, since the elastomer material in one axial end is drawn into the space, the tensile stress acting on the joint can be reduced.
The bond between the sleeve and the elastomer insert 31 can be prevented from being destroyed.

According to another embodiment of the invention, known techniques such as those shown in U.S. Pat. used. The elastomeric insert is preformed to have a thickness that is greater than the space between the inner and outer sleeves by a thickness corresponding to the desired degree of compression. A heat-activated adhesive is applied to the outer surface of the inner sleeve and the inner surface of the outer sleeve, and then an elastomeric insert is press-fitted between the sleeves, and the insert, with the adhesive heat-activated, is bonded to the sleeve. be done.

The elastomeric insert of the prior art central bushing is in a compressed state but is not adhesively bonded to the sleeve. Conventional bushings were tested by subjecting the elastomeric insert to accelerated forces similar to those encountered during actual use, as well as stresses due to movement of the inner and outer sleeves and their connected components, and no failure was observed. The embodiment showed a similar pattern as in actual use. On the other hand, similar tests conducted on the central bushing of the present invention revealed that the central bushing of the present invention
It has been found that it has a lifespan three to four times longer in actual use than conventional unbonded bushings.

[Effect on the invention] According to the invention, the elastomer insert is bonded to the inner and outer cylindrical sleeves and has annular ends that are not restricted in the axial and radial directions under any load condition. Therefore, if one of the wheels mounted on a tandem suspension encounters a bump or pothole in the road and becomes located at a different height than the other wheels, subjecting the elastomer insert to a torsional load. Also, under certain conditions, such as when the vehicle is turning, the inner cylindrical sleeve and the outer cylindrical sleeve are no longer in a coaxial relationship and a conical stress is applied to the elastomer insert. Wear, abrasion and destruction of the elastomer insert can be prevented. In particular, the annular end projecting axially from the space between the two cylindrical sleeves serves as a reservoir for the elastomeric insert, such that the inner and outer cylindrical sleeves are no longer in a coaxial relationship. This occurs at the joint between the cylindrical sleeve and the elastomeric insert because the elastomeric material in the annular end on one side is drawn into the space between the cylindrical sleeves when This has the advantage that the tensile stress caused by the elastomeric insert can be reduced and the bond between the cylindrical sleeve and the elastomer insert can be prevented from breaking.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of a tandem suspension system according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a central bushing according to the present invention showing the bushing in an unloaded state, and FIG. 3 is a conical suspension according to an embodiment of the present invention. FIG. 4 is a cross-sectional view similar to FIG. 2 showing the bushing under stress; FIG. 4 is a cross-sectional view showing another embodiment of the bushing under conical stress; FIG. 1 is a schematic diagram of a tandem suspension showing an axle and a wheel riding on a bump; FIG. 11, 12...equalized beam, 15, 16...
End bracket, 19...Central bushing, 24
...Inner sleeve, 30...Outer sleeve,
31...Insert body.

Claims (1)

[Claims for Utility Model Registration] (1) (a) a pair of parallel equalizing beams, (b) supporting means for supporting the ends of each of the equalizing beams, and (c) each of the supporting means. end brackets mounted on a pair of connected isolated parallel transverse axles;
(d) a central bushing disposed in the center of each said equalizing beam; and (e) frame bracket means connected to said equalizing beam by said central bushing, each said central bushing comprising: It consists of an inner cylindrical sleeve, an outer cylindrical sleeve, and a cylindrical elastomer insert inserted between and bonded to the two cylindrical sleeves, the elastomer insert being a first portion that occupies almost the entire space between the two cylindrical sleeves and is in a radially compressed state; and a second portion having an annular end that is directionally and radially unrestricted. (2) A utility model registration claim characterized in that one of the cylindrical sleeves is radially deformed over its entire axial length to place the elastomer insert in a radially compressed state. The tandem suspension system according to claim 1. (3) The tandem suspension system according to claim 1, wherein the elastomer insert is compressed in the direction of its wall thickness at least to the extent that shrinkage stress is removed. (4) The tandem suspension device according to claim 1, wherein the axial length of the elastomer insert is at least 12 times the thickness of the elastomer insert. (5) The tandem according to claim 1, wherein the inner cylindrical sleeve is stretched to a tensioned state, and the elastomer insert is in a compressed state. Suspension system. (6) The tandem suspension system according to claim 5, wherein the elastomer insert is compressed in the direction of its wall thickness at least to the extent that shrinkage stress is removed. (7) The tandem suspension system according to claim 5, wherein the axial length of the elastomer insert is at least 12 times the thickness thereof.