JPH0321511A - Strut type wheel suspension - Google Patents

Abstract

PURPOSE:To reduce bending moment generated at a strut part consisting of a cylinder and a rod by displacing an intersection between a line of action of ground load of a wheel and a line connecting the both end fitting parts of a lower arm to each other against the center line of the cylinder. CONSTITUTION:A cylinder 1 is installed on a supporting member 4 of a wheel 5, and a piston 2 is slidably inserted into the cylinder 1. A manifold block 6 extending toward the inside of a car body is fixed on the upper end of a piston rod 3. Also a sub rod 7 in parallel with the piston rod 3 is fixed in the neighborhood of the upper end part of the car body inside of the manifold block 6. The upper end of the sub rod 7 is mounted on a car body member through a strut mount 8 made of an elastic material. An intersection Po between a line of action of ground load of the wheel 5 and a line connecting the both end fitting parts of a lower arm 11 to each other is displaced against the center line of the cylinder 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a strut type wheel suspension system for automobiles. BACKGROUND OF THE INVENTION A strut-type wheel suspension system used as a wheel suspension system for automobiles includes a cylindrical strut body whose lower end is attached to a housing that supports the wheel, and a strut body fitted into the strut body so as to be expandable and contractible in the axial direction. It is composed of a rod whose upper end is attached to the vehicle body via an elastic material, and a coil spring interposed between the strut body and the rod, and the contraction movement of the strut body and rod as the wheel moves up and down. However, in a strut-type suspension system like the one described above, the line of action of the wheel's ground load is connected to the axis of the strut, and the attachment points at both ends of the lower arm are Since the intersection with the line is deviated, the ground load causes a bending moment in the strut, and the rod does not extend or contract smoothly with respect to the strut body, increasing wear on the sliding parts.
This causes problems such as reduced lifespan.

Conventionally, in order to deal with the above problems, the center line of the coil spring is offset laterally and outwardly from the center line of the strut, or the center line of the coil spring is inclined relative to the center line of the strut. Measures are being taken (for example, see Utility Model Application Publication No. 58-76406)
．． Problems to be Solved by the Invention In strut-type wheel suspension systems using coil springs as described above, it is not possible to reduce the bending moment generated in the strut due to the offset or inclination between the coil spring center line and the strut center line. However, the oil chamber of the gas spring section, in which the oil chamber and the sealed gas chamber are separated by a diaphragm, and the oil chamber of the oil cylinder are communicated via an orifice, and one end of the oil cylinder (for example, the bottom surface of the cylinder) is connected to the oil chamber of the oil cylinder through an orifice. part) to the housing that supports the wheels, and the other #
A (for example, a piston rod) is connected to each member on the vehicle body side, and oil flows between the oil cylinder and each oil chamber of the gas spring part through an orifice to generate an appropriate damping force against the vertical load. In a strut-type hydropneumatic suspension, which obtains a spring action by the volumetric elasticity of gas sealed in a gas chamber via a diaphragm, a springing moment occurs between the piston rod and the oil cylinder due to the ground load of the wheels. No reduction can be expected at all.

The present invention relates not only to hydropneumatic suspensions but also to strut-type wheel suspension systems that obtain a spring action using compressive elasticity of air sealed in coil springs or air chambers. The purpose of this is to provide a mechanism that can reduce the bending moment that occurs between the cylinder and the oil cylinder. Means for Solving the Problems The present invention provides a strut type wheel suspension device that includes a cylindrical member whose lower part is attached to a wheel side member, a rod slidably fitted into the cylindrical member, and an upper end of the rod. a sub-rod that is fixed to the upper part of the bracket on the inner side of the vehicle body so as to be parallel to the rod and whose upper part is attached to the vehicle body side member via a rubber mount; It is characterized by an object that is interposed between the member and the rod and that provides a spring action. Action According to the above, coil springs are used as members that provide spring action.
In all types of strut type wheel suspension systems that use air springs or hydropneumatic springs, etc., the intersection of the line of action of the wheel's ground load and the line connecting the attachment points at both ends of the lower arm deviates from the center line of the cylindrical member. Therefore, it is possible to reduce the bending moment generated in the strut section composed of the cylindrical member and the rod, and to achieve smooth expansion and contraction between the cylindrical member and the rod. Examples Examples of the present invention will be explained below with reference to the accompanying drawings. In Fig. 1.2, l is a cylinder whose lower part is attached to a wheel support member 4 that rotatably supports a wheel 5, 2 is a piston slidably fitted in the cylinder l, and 3 is a piston rod. , 6 is a manifold block that is fixed to the upper end of the piston rod 3 and extends inward of the vehicle body, 7 is a sub-rod that is fixed to the vicinity of the upper end of the manifold block 6 on the inner side of the vehicle body and runs parallel to the piston rod 3; The seventh end is attached to a vehicle body member (not shown) via a strut mount 8 made of an elastic material such as rubber.

Two upper and lower chambers in the cylinder 1 defined by the piston 2 are filled with oil, and the two upper and lower chambers communicate with each other through an orifice 2a provided in the piston 2 that does not generate damping force.

Moreover, the piston rod 3 has a hollow shape, and the hollow part 3
One end of a is connected to the cylinder 1 by the opening 2b of the piston 2.
The other end communicates with the oil chamber of the gas spring section (not shown) through a communication path 6a of the manifold block 6, a union block 9 swingably attached to the manifold block 6, and a hose 10. The strut consisting of the cylinder 1, piston 2, and piston rod 3 can be compressed by the oil flowing in and out through the communication passage, thereby changing the vehicle height. Reference numeral 7a is a bleeder passage provided on the sub-rod 7 and communicated with the communication passage 6a of the manifold block 6 for bleeding air during oil filling, and is covered with a cap (not shown) to prevent oil from flowing out when the air bleeding operation is completed. ．． l1 is the lower arm. First, the third example shows the case where the strut axis is not offset.
In the figure, the bending moments that cause friction occurring between the oil cylinder l and the piston 2 and between the rod guide la of the oil cylinder l and the piston rod 3 are determined.

Since the shaft attachment point FA of the lower arm 11 with the wheel support member 4 and the shaft attachment point Pa with the vehicle body side member are both pin-coupled so that they can swing in the vertical direction, the lower arm 1l
The force fa acting on can only be generated in the straight line direction connecting point P^ and point Pa. Therefore, the direction of the force fS that the piston rod 3 receives from the shaft attachment point Ps with the vehicle body side member is determined by the intersection point Po between the line of action of the wheel reaction force R and the extension line connecting the shaft attachment point P^ and Pa and the axis A force f acts on the lower arm 11 from a triangle of force balance, which is on a straight line connecting the landing point PS and with the road reaction force R as a reference.
a and the force fs exerted on the piston rod 3 are found. Or a wheel or wheel support member centered on the shaft attachment point FA. The rotational moment M^ of the strut system is determined by lr, which is the horizontal distance between the grounding point of the wheel 5 and the pivot point P^ of the wheel support member 4 of the lower arm 11, and the intersection point PG with the pivot point FA, the pivot point PS, and the pivot point P^ of the wheel support member 4 of the lower arm 11. If the distance from the straight line connecting is no, then M^=R
Represented by lr-fs Jio. However, force R and force f
The resultant force of s is force fa, and the line of action of force f1 passes through the intersection P^. Therefore, Ma = Rlr - fs fLo = f
1XO=0 On the other hand, the line of action of the force fa that pulls the lower arm 11 at the shaft attachment point P8 also passes through the shaft attachment point P^. From the above, this suspension system is stable due to the above forces R, fs, and fa. Next, find the forces f5 and fa. If the angle between the straight line connecting the intersection point Po and the axis attachment point P^ and the horizontal line is α, and the angle between the straight line connecting the intersection point Po and the axis attachment point Ps and the vertical line is β, then from the force balance condition, R= fscosβ-fa sin a --------
---(1) f5s:nβ= f a cos a
=(2) stands out. From this force f (S). (a
), we get . Force fs acting on the piston rod 3 at the shaft attachment point Ps
can be divided into a force fs^ in the axial direction of the piston rod 3 and a force fSP in the direction perpendicular to the axis of the piston rod 3. The bending moment of the piston rod 3 at the rod guide portion Pau due to the force fSP is fspXn, where n is the distance between the shaft attachment point PS and the rod guide PBU.
In order to support the piston rod 3 against this bending moment, a reaction force fBLl*fBL is generated in the rod guide part Pou and the contact part PBL between the cylinder l and the piston 2 in the direction shown by the arrow in FIG. 4, respectively. do. If the distance between the contact part PBL and the rod guide part Peu is m, and the angle between the straight line that connects the shaft attachment point Ps and the intersection Po and the 3rd axis of the 7 piston rod is 6, then fSp = fs sin e. The bending moment becomes. These reaction forces fau
, fo (by which piston rod 3 becomes oil cylinder 1
When the strut moves in and out and expands and contracts, sliding resistance of μfBU and Jif[]L occurs at the rod guide part F'ou and the abutment part pet of the piston 2 against the oil cylinder l, respectively (however, the (friction coefficient). Next, when offset from the strut shaft 3 of the sub-hydraulic 7 by Jls toward the inside of the vehicle body, the rod guide portion PB
u and oil cylinder 1 and piston 2 stop contact part PB
Let us consider the influence on the reaction forces fBLl and fsc generated at L. In FIG. 1, which shows the layout of the device of the present invention and the forces acting on various parts, a bending moment M=fS^●US is generated in the piston rod 3 by the axial force fS^ of the sub-rod 7 at the shaft attachment point PS, As a result, the rod guide portion PBU and the abutting portion pat between the oil cylinder 1 and the piston 2 have a size expressed by f. On the other hand, the influence of fsP is the same as in equations (5) and (6) when the strut axis is not offset. The sliding resistance at the rod guide portion Pal and the contact portion Pot is obtained by multiplying the magnitude of the force perpendicular to the piston rod 3 by the friction coefficient R, and the sliding resistance at the rod guide portion PBU and the contact portion Pot is calculated by multiplying the magnitude of the force perpendicular to the piston rod 3 by the friction coefficient The reaction force is obtained by superimposing the reaction forces shown in Figures 4 and 5. Therefore, the sliding resistance at the rod guide part Pou and the contact part Pet is {l feu-fMl +l fM-fetl} u-
Therefore, to minimize the sliding resistance, {l
It is sufficient to generate a bending moment M that produces a reaction force fM that minimizes feu−fH l + I fM−fetl}. The horizontal axis represents the reaction force fH generated in the rod guide portion P8U and the contact portion T'et when the axis of the sub-rod 7 is offset with respect to the strut axis 3, and the reaction force fH generated in the rod guide portion Pau and the contact portion PBL when not offset. Reaction force fe
In Figure 6, where u and fBL are taken on the vertical axis, Ifaυ
-fs I and lfH -feshil are respectively represented by a dashed line and a dashed double dotted line, so {I fou-fM l + l fM-foLl}
is shown as a solid line. Therefore, when f8υ≦fM≦fBL, the sliding resistance has the minimum value (
feυ-faL)g, it is possible to significantly reduce the sliding resistance (fau+fai)g when the strut axis is not offset. The reaction force fN generated by offsetting the strut axis in the above can be achieved by appropriately selecting the distance is between the strut axis 3 and the sub-rod axis 7. In the above embodiments, an example was described in which the application was applied to a hydro-pneumatic suspension device, but it goes without saying that the application can also be applied to a hydro-pneumatic active suspension device, and it can also be applied to a strut-type suspension device using a coil spring or an air chamber. Of course, it can also be applied. Effects of the Invention According to the present invention, a strut-type wheel suspension device includes a cylindrical member whose lower portion is attached to a wheel side member, a rod slidably fitted in the cylindrical member, and an upper end of the rod. a bracket that is fixed and extends inward of the vehicle body; a Zabro rod that is fixed to the upper part of the bracket on the inner side of the vehicle body so as to be parallel to the rod, and whose upper part is attached to the vehicle body side member via a rubber mount; and the cylindrical member. and an object that provides a spring action interposed between the rod and the rod.
In all types of strut-type wheel suspension systems that use coil springs, air springs, or oil-pneumatic springs as members that provide spring action, the line of action of the ground load of the wheel and the attachment points at both ends of the lower arm are connected to the center line of the cylindrical member. Since the intersection with the connecting line is offset, the bending moment generated in the strut section consisting of the cylindrical member and the rod can be reduced, and smooth expansion and contraction can be achieved between the cylindrical member and the rod. Combined with its simple structure, it can bring great practical effects.

[Brief explanation of drawings]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a sectional view of the main part of Fig. 1, and Fig. 3 is an explanation showing the situation of loads and reaction forces acting on each part when no sub-rod is provided. Fig. 4 is a bending moment diagram when no sub-rod is provided, Fig. 5 is a bending moment diagram when a sub-rod is provided, and Fig. 6 is a bending moment diagram when the sub-rod is provided. FIG. 3 is an explanatory diagram showing the influence on the reaction force fBU or fBL generated between DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Piston, 3... Piston rod, 4... Wheel support member, 5... Wheel, 6...
・・Manifold block, 7・・Sub rod, 8・
...Strut mount, 9...Union block,
1O...Hose, 1L...Lower arm. 21XJ Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A cylindrical member whose lower part is attached to the wheel side member, a rod slidably fitted into the cylindrical member, a bracket fixed to the upper end of the rod and extending inward of the vehicle body, and the vehicle body of the bracket. A sub-rod that is fixed to the inner upper part in parallel with the rod and whose upper part is attached to the vehicle body side member via a rubber mount, and an object that provides a spring action that is interposed between the cylindrical member and the rod. A strut type wheel suspension system comprising: (2) A patent claim characterized in that the object that provides the spring action is a fluid such as air in an air spring or oil in a hydropneumatic spring, and the rod and bracket are provided with a flow path for the fluid. The strut type wheel suspension system according to item 1.