JP2007313974A - Suspension device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension device which realizes the sharp improvement of riding comfort without decreasing driving stability. <P>SOLUTION: The suspension device is constituted by arranging an elastic support means to allow a working position of the resultant force of the elastic support means (front and rear springs 5) which suspends an axle 3 on the vehicle body side (frame 1 side) to be off-set in one of front and rear directions of a vehicle from a position of the center of gravity of an unsprung mass with a required interval and by allowing an unsprung pitch moment generated around the center of gravity of the unsprung mass to be accepted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a suspension device.

  5 and 6 show an example of a rear suspension device in a large vehicle such as a truck or a bus. Below the pair of left and right frames 1 extending in the front-rear direction of the vehicle body (the left-right direction in FIG. 5), An axle 3 extending in the width direction (vertical direction in FIG. 6) and supporting the tire 2 at both ends thereof is arranged, and a support beam integrally assembled on the lower surface near the end of the axle 3 An air spring 5 that absorbs vibration in the vertical direction is interposed between the front and rear end portions of 4 and the lower surface of the frame 1.

  Further, a bracket 6 extending downward is attached to the frame 1 further forward of the air spring 5 disposed on the front side, and a gap between the lower end portion of the bracket 6 and the intermediate portion of the support beam 4 is The stabilizer 7 is connected to be tiltable by a stabilizer 7 that increases the roll rigidity of the vehicle body.

  That is, the stabilizer 7 shown here is generally referred to as a lower rod-integrated stabilizer, and is a hollow pipe (hollow shaft) rotatably installed between the lower end portions of the left and right brackets 6. A stabilizer bar 8 comprising: an arm 9 having one end fixed to both ends of the stabilizer bar 8 and connected to a bracket 10 provided at the other end of the support beam 4 via a rubber bush. The left and right tires 2 are bridged in a U-shape, and when the left and right tires 2 move up and down at the same time, the stabilizer bar 8 rotates relative to the bracket 6 and the stabilizer 7 Although it does not work in particular, a torsional moment acts on the stabilizer bar 8 when the left and right tires 2 move differently due to cornering or the like, and the reaction force So that the form works like return the left and right of the tire 2 to the original.

  Here, the arm 9 in the stabilizer 7 also has a function of determining the position and angle of the axle 3 as a lower torque rod, so that it is not necessary to separately provide a lower torque rod. With the arm 9 alone, it is difficult to reliably suppress the rotational moment (braking force or driving force) around the axle 3 and the lateral displacement moment applied to the axle 3.

  Therefore, the upper surface of the central portion of the axle 3 and the inner side surfaces of the left and right frames 1 are connected by a V rod 12 that functions as an upper side torque rod. More specifically, A branch end 12a (front end) separated from the left and right sides of the V rod 12 is connected to a bracket 13 extending from the inner side surface of the left and right frames 1 via a rubber bush, and is bent at the center of the V rod 12. The end portion 12b (rear end portion) is connected to a bracket 14 provided on the upper center portion of the axle 3 via a rubber bush.

  If such a V-rod 12 is employed, it is possible to cope with input in both the front-rear direction and the left-right direction of the vehicle body, so that a parallel-link type torque rod is employed. As a countermeasure against horizontal input, there is no need to install a lateral rod separately, and because the lower arm 9 is offset upward, the rotational moment about the axle 3 is reduced. It becomes possible to suppress it reliably.

  The middle part of the support beam 4 and the frame 1 immediately above it are connected by a shock absorber 11 extending in the vertical direction, and the shock absorber 11 suppresses the back-up of vibration in the vertical direction. Vibration damping is achieved.

  The basic design concept of such a conventional suspension system is to correspond to the position of the center of gravity of the unsprung mass, which represents the mass of the portion below (the tire 2 side) of the suspension spring (air spring 5 in the illustrated example). The axle 3 is arranged, and the air spring 5 is arranged in a well-balanced position in the front-rear direction across the axle 3 so that an unsprung pitch moment does not occur as much as possible around the center of gravity of the unsprung mass. there were.

The prior art document information relating to the basic design concept of this type of suspension device includes the following.
Edited by the Japan Society of Mechanical Engineers, New Technology Fusion Series (Volume 5), “Dynamics and Control of Vehicle Systems”, Yokendo Co., Ltd., 1999, p. 27-29

  However, in such a conventional design concept, since the unsprung pitch moment is suppressed as much as possible around the center of gravity of the unsprung mass, only the vertical displacement of the axle can be allowed. There was a limit to improving the ride comfort of the suspension system based on the design concept.

  Because, in order to improve the riding comfort of the suspension device based on the existing design philosophy, the air spring 5 must be enlarged to reduce the spring constant, but the spring function can be improved by reducing the spring constant in this way. This is because if the vehicle becomes too soft, a phenomenon such as rolling is likely to occur in the vehicle body, which may cause a decrease in steering stability.

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

  The present invention provides the elastic support means such that the acting position of the resultant force of the elastic support means for suspending the axle on the vehicle body side is offset from the position of the center of gravity of the unsprung mass to either one of the vehicle longitudinal direction with a required interval. And a suspension device that is configured to allow an unsprung pitch moment generated around the center of gravity of the unsprung mass.

  Thus, in this way, the position of the resultant force of the elastic support means is offset to either one of the vehicle longitudinal direction with respect to the position of the center of gravity of the unsprung mass. An unsprung pitch moment occurs around the center of gravity of the spring, and a stroke corresponding to the pitch angle of the unsprung pitch moment (the amount of offset of the applied position of the resultant force of the elastic support means with respect to the center of gravity of the unsprung mass, The stroke is calculated by multiplying the elastic support means as a single mechanically equivalent spring, and the apparent spring constant (dynamic motion) is superimposed on the stroke corresponding to the pitch angle. The spring constant) is reduced, and the impact input from the road surface is less likely to be transmitted to the vehicle body than before, greatly improving riding comfort. It will be.

  Moreover, even if the apparent spring constant is reduced by intentionally inducing the unsprung pitch moment in this way, the relative displacement of the axle itself with respect to the vehicle body in the vertical direction can be kept small. It is possible to avoid problems such as the occurrence of a phenomenon easily, and to avoid a situation that leads to a decrease in steering stability.

  Furthermore, in the present invention, the tire is preferably arranged so that the center position of the tire pivotally supported by the axle is offset from the center of gravity position of the unsprung mass to the other in the vehicle front-rear direction with a predetermined interval.

  In this way, since the center position of the tire is offset to the side opposite to the side where the resultant position of the resultant force of the elastic support means is offset with the center of gravity position of the unsprung mass as a base point, the offset on the tire side further increases. The unsprung pitch moment is induced, and the pitch angle of the unsprung pitch moment becomes larger even for the same impact input from the road surface.

  As a result, the stroke corresponding to the increased pitch angle is superimposed on the stroke when the tire is regarded as one mechanically equivalent spring, and the apparent spring constant is further reduced. This will improve the riding comfort more effectively.

  According to the suspension device of the present invention described above, the unsprung pitch moment is adopted by adopting a novel design philosophy that allows the unsprung pitch moment generated around the center of gravity of the unsprung mass without being bound by the existing design philosophy. Since the apparent spring constant (dynamic spring constant) can be reduced by deliberately guiding the vehicle, the shock input from the road surface is less likely to be transmitted to the vehicle body than before, and the riding comfort is greatly improved. In addition, while reducing the apparent spring constant, the relative displacement of the axle itself with the vehicle body in the vertical direction can be kept small, making it difficult for rolling and other phenomena to occur in the vehicle body. It is possible to obtain an excellent effect that it is possible to avoid a situation that causes a decrease in stability.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 4 show an example of an embodiment for carrying out the present invention, and parts denoted by the same reference numerals as those in FIGS. 5 and 6 are functionally the same even if there is a difference in shape. It represents.

  As shown in FIG. 1, in the suspension device of this embodiment, air springs 5 are interposed between the front and rear ends of the support beam 4 and the lower surface of the frame 1 as in the case of the conventional FIG. The axle 3 is arranged so as to be shifted rearward from the intermediate portion of the support beam 4, and the front and rear air springs 5 are asymmetrically arranged with the axle 3 as a base point.

As a result of the asymmetrical arrangement of the front and rear air springs 5 with the axle 3 as a base point, the acting position of the resultant force of each air spring 5 is below the unsprung mass (lower than the air spring 5 forming the suspension spring [tire It is offset at a predetermined distance forward from the center of gravity of the mass of a portion of the 2 side]), also in the rear from the center of gravity position of the center position T _o spring under the weight of the tire 2 which is rotatably supported by the axle 3 It is offset by a required interval.

That is, the actual structure of FIG. 1 can be simplified as a vibration system model as shown in FIG. 2. If the front and rear air springs 5 of FIG. 2 are regarded as one mechanically equivalent spring, the equivalent spring of FIG. 5 ′, the arrangement position of the equivalent spring 5 ′ (the position where the resultant force of the air spring 5 before and after FIG. 2 acts) is the required distance L _S from the center of gravity O of the unsprung mass to the front. It is offset with a gap.

Further, when the tire 2 pivotally supported by the axle 3 in FIG. 1 is regarded as one mechanically equivalent spring, it can be expressed as an equivalent tire spring 2 ′ in FIG. 2 or FIG. The position of '(the center position T _o of the tire 2 in FIG. 1) is offset from the center of gravity O of the unsprung mass backward by a required distance L _T (see FIG. 3).

  Further, in the actual structure of FIG. 1, the arm 9 of the stabilizer 7 that functions as a torque rod on the lower side is connected so as to be tiltable at a position closer to the front side than the middle portion of the support beam 4, and the torque on the upper side. A bent end portion 12b (rear end portion) at the center of the V rod 12 functioning as a rod is connected to a bracket 14 provided at the upper center portion of the axle 3 at a position behind the axle 3.

Then, As a result of placing the arms 9 and V rod 12 of the stabilizer 7, Tore static balance which collapsed by the offset of the center position T _o of the working position and the tire 2 of the resultant force of the air springs 5 above support The horizontal posture of the beam 4 is kept stationary, and the spring 3 is unsprung when an impact is input from the road surface while suppressing the rotational moment (braking force and driving force) around the axle 3 and the lateral displacement moment. The unsprung pitch moment M (see FIGS. 2 and 3) generated around the center of mass of the mass can be allowed to follow the unsprung pitch moment M.

  If an appropriate differential pressure is set for the front and rear air springs 5 by a differential pressure valve or the like, static balance is easily achieved, and the initial load applied to the arm 9 and the V rod 12 of the stabilizer 7 is increased. It will be less.

  Here, when the arm 9 and the V rod 12 of the stabilizer 7 are simplified as a vibration system model, it becomes as shown in FIG. 2, and furthermore, the arm 9 and the V rod 12 of the stabilizer 7 are converted into one mechanically equivalent spring. From the perspective, it can be expressed as the equivalent arm spring 9 'in FIG.

  The shock absorber 11 is disposed so as to be connected vertically to the frame 1 immediately above the axle 3 in the support beam 4 so as to allow vertical movement while allowing the unsprung pitch moment M described above. Abnormal vibrations due to direction swings can be reliably suppressed.

Thus, if the suspension device is configured in this way, the position of the resultant force of the air spring 5 is offset forward with respect to the center of gravity O of the unsprung mass. An unsprung pitch moment M occurs around the center of gravity, and a stroke corresponding to the pitch angle θ of this unsprung pitch moment M (a tilt angle from a stationary state when tilted to a position indicated by a one-dot chain line in FIG. 3) ( An offset amount L _{S of the applied} position of the resultant force of the air spring 5 with respect to the center of gravity O of the unsprung mass is a stroke calculated by multiplying the pitch angle θ of the unsprung pitch moment M), and the air spring 5 is mechanically moved. The stroke corresponding to the pitch angle θ is superimposed on the stroke when considered to be one spring equivalent to (equivalent spring 5 ′). Multiplying the spring constant (dynamic spring constant) is reduced, the shock input from the road surface so that a significant improvement in ride comfort is difficult to be transmitted to the vehicle body than conventional is achieved.

  Moreover, even if the apparent spring constant is reduced by intentionally inducing the unsprung pitch moment M in this way, the relative displacement of the axle 3 itself with respect to the vehicle body side (the frame 1 side) can be kept small. Therefore, it is possible to avoid problems such as the occurrence of a phenomenon such as rolling on the vehicle body in advance, and it is possible to avoid a situation that leads to a decrease in steering stability.

Here, for convenience of explanation, the case where the pitch angle θ of the unsprung pitch moment M is all caused by the offset amount L _S is described. However, in the present embodiment, the center position of the tire 2 is described. since T _o is also from the gravity center position O of the unsprung mass is offset at a predetermined distance L _T to the rear, the additional unsprung pitch moment M is induced by the offset amount L _T of the tire 2 side Therefore, the pitch angle θ of the unsprung pitch moment M is larger for the same impact input from the road surface.

  As a result, the stroke corresponding to the increase in the pitch angle θ is superimposed on the stroke when the tire 2 is regarded as one mechanically equivalent spring (equivalent tire spring 2 ′). As a result, the apparent spring constant is further reduced, and the riding comfort is improved more effectively.

  In fact, when the present inventors verified by the analysis based on the equivalent simplified model of FIG. 3, it was confirmed that the result shown in the graph of FIG. 4 was obtained, and the horizontal axis of this graph represents the frequency of vibration ( The speed of vibration input from the road surface), the vertical axis indicates the magnitude of vibration transmitted to the vehicle body, the solid line curve in the graph indicates that the unsprung pitch moment M is allowed, and the chain line curve is unsprung. The case where the pitch moment M is not allowed is shown.

  As can be seen from the graph of FIG. 4, the magnitude of vibration transmitted to the vehicle body (the zero level on the vertical axis means that the input from the road surface is transmitted to the vehicle body as it is, and there is vibration absorption below the zero level. This means that when the unsprung pitch moment M is allowed (solid line), a better vibration absorption effect can be obtained in a wider frequency range than when the unsprung pitch moment M is allowed (solid line). It was confirmed that riding comfort can be improved by intentionally inducing the moment M.

  In addition, as described in Non-Patent Document 1 mentioned above as the prior art document, it exists in the peak (the right peak of the two peaks) formed on the higher frequency side in the graph of FIG. What is referred to as the “fixed point” is considered to be a fixed point that exists regardless of the suspension parameter selected, but the spring generated around the center of gravity of the unsprung mass as in this embodiment. If a new design concept that allows the lower pitch moment M to be adopted is adopted, this “fixed point” does not appear, and it has been confirmed that the vibration level in the vicinity of the frequency can be lowered.

  Therefore, according to the above embodiment, the unsprung pitch moment M is adopted by adopting a new design concept that allows the unsprung pitch moment M generated around the center of gravity of the unsprung mass without being bound by the existing design concept. Since the apparent spring constant (dynamic spring constant) can be reduced by deliberately guiding the vehicle, the shock input from the road surface is less likely to be transmitted to the vehicle body than before, and the riding comfort is greatly improved. In addition, while reducing the apparent spring constant, it is possible to suppress the relative displacement of the axle 3 itself with respect to the vehicle body side in the vertical direction so that a phenomenon such as rolling does not easily occur in the vehicle body. It is possible to avoid a situation that causes a decrease in steering stability.

  The suspension device of the present invention is not limited to the above-described embodiment. In the illustrated example, the acting position of the resultant force of the air spring before and after forming the elastic support means is offset forward from the center of gravity position of the unsprung mass. However, in this case, it is possible to offset backward, and in such a case, the center position of the tire may be offset forward, The elastic support means is not necessarily composed of a pair of front and rear air springs, and the position where the resultant force is applied is offset from the position of the center of gravity of the unsprung mass to either one of the longitudinal direction of the vehicle with a required interval. The type of the elastic support means is not particularly limited as long as it is adapted, and other various modifications can be made without departing from the scope of the present invention. As a matter of course.

It is a side view which shows an example of the form which implements this invention. It is the schematic diagram which simplified the suspension apparatus of FIG. 1 as a vibration system model. It is a schematic diagram which shows the equivalent simple model of the vibration system model of FIG. It is a graph which shows the analysis result based on the equivalent simple model of FIG. It is the schematic which shows a prior art example. FIG. 6 is an arrow view in the VI-VI direction of FIG. 5.

Explanation of symbols

1 frame 2 tire 3 axle 5 air spring (elastic support means)
The center position of the L _S distance L _T interval M unsprung pitch moment O centroid position T _o tire

Claims (2)

  The elastic support means is disposed so that the position of the resultant force of the elastic support means for suspending the axle on the vehicle body side is offset from the center of gravity position of the unsprung mass to either one of the vehicle longitudinal direction with a required interval, A suspension apparatus characterized by being configured to allow an unsprung pitch moment generated around the center of gravity of the unsprung mass.   2. The tire according to claim 1, wherein the tire is disposed such that a center position of the tire pivotally supported by the axle is offset from the center of gravity position of the unsprung mass to the other in the vehicle front-rear direction with a predetermined interval. Suspension device.

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