JP2007084070A - Rear wheel suspension device of automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear wheel suspension device which includes a multi-link type rear suspension A configured so that a wheel support 11 is coupled to a body of automobile through five links 6-10, and rubber bushings 26 are installed at the body side ends of the links, and generates a sharp drive feeling applicable even to a sports car while the merit of fine comfortableness owing to interposing of the rubber bushings 26 is well made use of. <P>SOLUTION: The bottom of a shock absorber device 14 where a coil spring 12 and a damper 13 are installed approximately coaxially, is pivoted at the end of a coupling part 30 extended inside the body of a wheel support 11 of each rear wheel 2, and a virtual king pin shaft K of the rear wheel 2 is set so that the vertical reaction force generated there will generate a moment in the rear wheel 2 in the toe-in direction. To the rear wheel 2 which is positioned in the rear in turning with the caster trail in a negative value, a moment in the toe-in direction is arranged to act directly by a lateral force. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automobile rear wheel suspension device, and more particularly to a multi-link suspension constituted by five I links.

2. Description of the Related Art Conventionally, as a multilink suspension, there are known five I-links each having an elastic bush at least at the end of the vehicle body (see, for example, Patent Document 1). In such a multi-link suspension composed of five I-links, each I-link is arranged so as to optimally constrain the five degrees of freedom of movement excluding the vertical stroke of the rear wheel in accordance with each requirement. Therefore, it can be said that the suspension type has a high performance potential.
JP-A-2-38106

  However, the multi-link type suspension has a problem in rigidity because of its high degree of freedom, and the problem becomes remarkable particularly in the structure in which the link is attached via the elastic bush as described above. That is, when the wheel receives a lateral force when the vehicle is turning, the elastic bush of each link is bent, so that the rigidity is lowered, and the movement of the suspension is delayed by the amount of the bending.

  In addition, the position (alignment) of the wheel determined by the geometrical arrangement of each link changes strictly by the amount of bending of the elastic bush, but what load is input because of the high degree of freedom. However, it was extremely difficult to manage the design so as to bend in the optimal direction, and it was difficult to obtain the expected suspension performance.

  For these reasons, multi-link suspensions are used in high-end sedans that place greater emphasis on ride comfort than steering stability and require higher straight-running stability at extremely high speeds than turning performance. In general, it is not used in sports cars, etc., which have strict requirements for maneuvering stability and absolute turning performance compared to requirements related to ride comfort.

  In such a multi-link suspension, when all of the suspensions are connected to the vehicle body or the like by using a ball joint without using an elastic bush, there is no elastic deformation due to bending that cannot naturally be managed by design. Needless to say, not only can the alignment accuracy be maintained, but the alignment accuracy can be maintained as well, and combined with the high potential of the base, excellent steering stability can be exhibited. However, since vibration and noise cannot be cut off at all by the elastic bush, road noise, noise generated by resonance of each I link, etc. are all transmitted to the vehicle body, and the practicality as a passenger car cannot be secured. In a sense, even though it is a sports vehicle, it is difficult to adopt five multi-link suspensions for a commercial vehicle that requires a vibration / noise blocking performance.

  In view of such a point, the object of the present invention is to provide a sporting performance that is required to be high in a multi-link type rear wheel suspension device including five links having elastic bushes at least at an end on the vehicle body side. The aim is to provide a multi-link suspension based on completely new knowledge that can obtain sufficient vibration and isolation performance as a commercial vehicle while ensuring high steering stability applicable to such vehicles.

  In order to achieve the above object, in the rear wheel suspension device according to the present invention, the moment force in the direction of the toe-in is applied to the rear wheel of the vehicle in advance using the vertical reaction force of the shock absorber, and at the time of turning of the vehicle. A moment force in the direction of toe-in is applied directly to the rear wheel located outside the turn by a lateral force.

  Specifically, in the invention of claim 1 of the present application, a support member for a rear wheel of an automobile is connected to a vehicle body by five links, and an elastic bush is disposed at least at an end portion of the vehicle body side of each link. And a multi-link type rear wheel suspension device in which the upper end side of the shock absorber generating the vertical reaction force is attached to the vehicle body side and the lower end portion is pivotally attached to the vehicle body inward side of the rear wheel support member. To do. Then, the virtual kingpin shaft of the rear wheel is set so that a moment force in the toe-in direction is generated around the virtual kingpin shaft by the vertical reaction force of the shock absorber, and the caster trail has a negative value. Is set.

  With the above configuration, first, the rear wheel suspension device of the automobile is a five-link multi-link type, so that it is possible to optimally restrain the five degrees of freedom of movement of the rear wheels. In addition to having a higher potential than that using an H-arm, it is possible to obtain an excellent ride comfort by interposing an elastic bush.

  In addition, a moment force in the direction of toe-in is applied to the rear wheel by the reaction force of the shock absorber via the support member, and the elastic bushing of each link is urged (precompressed) in the direction of the toe-in of the wheel in advance. Therefore, it becomes possible to immediately apply toe-in to the rear wheels outside the turn by eliminating the delay caused by the bending of the elastic bush when turning the automobile. As a result, the multi-link suspension has a phase lag that is unprecedented in the past, that is, a sharp driving feeling with extremely high rigidity and responsiveness.

  That is, in general, when the driver steers, a lateral acceleration is generated in the automobile, and a load movement to the outside of the turn is generated accordingly, and a cornering force is generated in each wheel. If the toe-in is applied to the rear wheels by this force at the stage of load movement that is earlier than the stage at which cornering force is generated, that is, when the vertical reaction force is generated in the shock absorber, the generation of cornering force is accelerated. As a result, the phase delay is reduced.

  Thus, in order to urge the rear wheel in the toe-in direction by the vertical reaction force of the shock absorber, it is necessary to appropriately set the direction of the reaction force and the point of action of the rear wheel on the support member with respect to the virtual kingpin axis. There is. For example, the virtual kingpin shaft of the rear wheel is tilted so that the upper end side is located at the rear of the vehicle body, and the shock absorber is positioned inward of the vehicle body with respect to the virtual kingpin shaft and the virtual kingpin shaft It is only necessary to arrange them so that they are not parallel to each other and do not intersect with each other, and the direction of the axis is closer to the vertical than the virtual kingpin axis when viewed from the side of the vehicle body.

  In the above configuration, the virtual kingpin shaft of the rear wheel is set so that the caster rail has a negative value, and when viewed from the side of the vehicle body, the intersection of the virtual kingpin shaft and the road surface is from the grounding point of the rear wheel. Is also located behind the car body. As a result, the point of application of the lateral force to the rear wheel is located in front of the vehicle body relative to the virtual kingpin shaft, and the moment force in the toe-in direction is generated directly by the lateral force. That is, toe-in by a lateral force can be applied to the rear wheel outside the turning of the automobile, and the behavior can be stabilized.

  In other words, the urging force in the direction of toe-in is given to the rear wheel in advance by the reaction force of the shock absorber, and the moment force in the direction of toe-in due to the lateral force also acts on the rear wheel outside the corner when turning, In this way, a consistent driving sensation and a high sense of stability can be obtained by being constantly biased toward the toe-in direction.

  In the rear wheel suspension device as described above, it is more preferable that the shock absorber is separated from the rear wheel inward of the vehicle body so that the vertical reaction force generates a moment force in the negative camber direction with respect to the rear wheel. In addition, the moment force in the direction of the negative camber due to the vertical reaction force is compared with the moment force in the direction of the positive camber generated by the lateral force at the rear wheel located outside the turn when the vehicle is turning. It is to set so as to increase to the limit area.

  In this way, due to the vertical reaction force of the shock absorber, a moment force in the direction of the negative camber acts on the rear wheel via its support member, and this moment force is also applied to the rear wheel outside the turning of the automobile. Since it always becomes larger than the moment force of the positive camber due to the lateral force up to the limit region of the lateral force, the urging force of a constant direction always acts on the elastic bush of each link of the rear wheel with respect to the camber change. As a result, microscopic wheel wobble does not occur, and driving feelings and unnatural behavior are eliminated, and a rear wheel suspension device with unprecedented steering stability can be realized.

  In order to apply a moment force in the direction of the negative camber to the rear wheel by the vertical reaction force of the shock absorber, the lower end of the shock absorber is pivoted to the inside of the rear wheel support member, The vertical reaction force may be applied to a position below the center of the rear wheel, but on the other hand, the moment of the positive camber direction is applied directly to the rear wheel, which is located outside the turn when the vehicle is turning, by the lateral force. Force is generated. At this time, the roll of the vehicle body becomes larger in proportion to the increase of the lateral force acting on the rear wheel, and the reaction force increases by compressing the coil spring of the shock absorber, so the moment force of the negative camber also increases. Eventually, at the rear wheel outside the turn, the moment force of the positive camber due to the lateral force increases as the lateral acceleration of the vehicle increases, and the moment force of the negative camber due to the vertical reaction force of the shock absorber increases.

  Therefore, the load of the rear wheel outside the vehicle's turning, the maximum grip force of the rear wheel, the hardness of the coil spring of the shock absorber (spring constant), or the arm of moment force generated on the rear wheel by the shock force of the shock absorber If the length of the motor is appropriately set in relation to each other, a sufficiently large negative camber moment force can be applied to the rear wheel by the vertical reaction force of the shock absorber. The moment force of the positive camber due to the lateral force can be increased to the limit region.

  More specifically, the moment force in the direction of the negative camber acting on the rear wheel due to the vertical reaction force of the shock absorber is the distance from the axis of the shock absorber to the center of the rear wheel (the length of the arm of the moment). Expressed as the product of the shock absorber reaction force. Here, the vertical reaction force of the shock absorber itself is determined on the basis of the shared load on the rear wheels and the hardness of the coil spring, that is, the roll characteristics of the automobile, so the moment force in the direction of the negative camber should be sufficiently increased. Then, it is necessary to increase the length of the arm substantially. Therefore, for example, assuming a limit region where the maximum lateral acceleration is generated in the rear wheel when the vehicle is turning, the shock absorber reaction force is greater than the moment force of the positive camber acting on the rear wheel due to the limit lateral force at that time. Therefore, the length of the arm of the moment may be set so that the moment force of the negative camber due to.

  In the rear wheel suspension device having the above-described configuration, it is more preferable that the lower end portion of the shock absorber is pivotally attached to the front end of a connecting portion that is integrally formed so as to extend inward from the rear wheel support member. It is. That is, in order to apply a large moment force to the rear wheel by the vertical reaction force of the shock absorber, it is preferable to extend the connecting portion from the support member of the rear wheel to the inside of the vehicle body. By integrally molding, it is possible to reduce the weight while securing the strength, and it is possible to suppress an increase in so-called unsprung weight.

  Preferably, the connecting portion is viewed from the front and rear direction of the vehicle body, and extends from the upper and lower ends of the support member body of the rear wheel toward the inner side of the vehicle body, and is integrated with the upper arm portion and the lower arm portion at the front end portion. And an intermediate arm portion extending in the vertical direction so as to connect the upper arm portion and the lower arm portion at each intermediate portion in the vehicle width direction, and a support shaft constructed from the intermediate arm portion to the tip of the connecting portion. The end portion of the shock absorber is protruded inward of the vehicle body, and the lower end portion of the shock absorber is attached thereto.

  In this configuration, first, the connecting portion is made of a substantially A-shaped sideways composed of an upper arm portion, a lower arm portion, and an intermediate arm portion, thereby reducing the weight while ensuring sufficient rigidity against the load in the vertical direction. Can do. Then, by attaching the shock absorber to the support shaft attached at two points with a sufficiently large distance from the A-shaped horizontal bar (intermediate arm) to the tip, the vertical reaction force of the shock absorber Can be reliably transmitted to the rear wheels.

  Further, it is preferable that the shock absorber is arranged so that the urging force in the longitudinal direction of the vehicle body acting on the rear wheel by the vertical reaction force is minute or zero.

  In this way, even if the vertical reaction force acting on the rear wheel support member from the shock absorber is very large, the force in the vehicle longitudinal direction acting on the rear wheel can be made minute by this force. As a result, the displacement of the rear wheels in the front-rear direction is not restricted excessively while the automobile is running, and a good riding comfort can be obtained against road surface irregularities and the like. In other words, the inclination angle of the shock absorber shaft center and the distance in the longitudinal direction of the vehicle body from the center of the rear wheel are set so that the longitudinal force on the rear wheel generated by the vertical reaction force of the shock absorber is sufficiently small. What is necessary is just to set experimentally according to requirements, such as comfort.

  Specifically, the shock absorber is preferably arranged so that its axial center extends in a substantially vertical direction when viewed from the side of the vehicle body. In this way, even if the vertical reaction force of the shock absorber is extremely large, it does not directly apply the longitudinal force to the rear wheel. Further, the shock absorber may be inclined so that the upper end side of the shock absorber is positioned inward of the vehicle body when viewed in the longitudinal direction of the vehicle body, and disposed at a predetermined distance from the vehicle wheel inward side of the rear wheel support member. .

  Or you may arrange | position a buffering device so that a rear wheel may be urged | biased by the vehicle body front by the vertical reaction force. That is, the most important point in the present invention is that the vertical reaction force of the shock absorber acts on the rear wheel in the toe-in direction in the multilink type rear wheel suspension device as described above. Although the longitudinal force acting on the rear wheel can be reduced by the reaction force of the shock absorber, it may not be reduced to zero.

  Therefore, if the direction of the longitudinal force acting on the rear wheel is directed toward the front of the vehicle, the urging force toward the front of the vehicle acts on the elastic bush of each link of the rear wheel. . In this state, when a shock due to road surface irregularities or the like is input to the rear wheel, the direction of the force acting on the elastic bush is reversed and the elastic bush is bent in the opposite direction, so that the rear wheel is displaced rearward and the shock is applied. You will be able to escape. Therefore, it is possible to obtain a good ride comfort.

  Preferably, the shock absorber is disposed such that its axial center is positioned rearward of the rear wheel center when viewed from the side of the vehicle body, and the elastic bush of the lower link of the five links is disposed on the upper link. It is to be soft compared to the elastic bush.

  In this way, a moment force around the rear wheel shaft center is generated in the support member by the vertical reaction force of the shock absorber, and this moment force is applied to the upper link and the lower link supporting the rear wheel in the longitudinal direction of the vehicle body, respectively. Will be granted. That is, for example, when the rear wheel is viewed from the left side of the vehicle body, the vertical reaction force of the shock absorber acts on the support member from the substantially vertical upper side on the right side (rear side of the vehicle body) from the rear wheel center. As a result, a clockwise moment force is generated. This moment force biases the upper link toward the right side (rear side of the vehicle body) and exerts a biasing force toward the rear side of the vehicle body on the elastic bush, while the lower link is biased toward the left side (front side of the vehicle body). A biasing force toward the front of the vehicle body acts on the elastic bush.

  And, by making the elastic bush of the lower link relatively soft, when a shock due to road surface irregularities or the like is input to the rear wheel, the elastic bush of the lower link bends in the reverse direction due to the reversal of force, thereby Displacement toward the rear of the vehicle body is allowed, and this makes it possible to obtain a good riding comfort.

  Such an action is particularly effective when the rear wheel is a driving wheel of an automobile. That is, as described above, when the elastic bushing of the predetermined link of the rear wheel is urged in front of the vehicle body in advance by the vertical reaction force of the shock absorber, if the rear wheel is a driving wheel, the acceleration of the automobile, etc. This is because when a driving force (a forward force) is applied to the vehicle, the delay due to the bending of the elastic bushing is reduced, and the acceleration response of the automobile to the accelerator operation is improved.

  In addition, when the vehicle is accelerated, the bump amount of the rear wheel suspension is increased by the squat of the vehicle body, thereby compressing the coil spring of the shock absorber, so that the shock absorber according to the increase in the bump amount, that is, according to the increase in driving force. The vertical reaction force increases. Therefore, the urging force to the elastic bush increases as the acceleration accelerates, and a high acceleration response can be obtained without delay even for a large driving force.

  On the other hand, if the elastic bushing is urged in front of the vehicle body in advance as described above, when braking force (backward force) is applied from the road surface to the rear wheel during braking of the automobile, this braking force is applied to the urging force. The braking force is transmitted to the vehicle body only after it has been overcome and the direction of bending of the elastic bushing is reversed, so there is a risk that braking of the vehicle body will be delayed and the brake feeling will deteriorate.

  However, when the vehicle is braked, the nose dive of the vehicle body increases the amount of rebound of the rear wheel suspension device, and accordingly, the vertical reaction force of the shock absorber decreases as the braking force increases. The urging force to the elastic bush due to the reaction force is also reduced, and the direction of the bending of the elastic bush is quickly reversed by that amount. Consequently, it is considered that the deterioration of the brake feeling is not a problem.

  It should be noted that, depending on the arrangement of the links and the shock absorbers, the shaft center of the shock absorber may be separated from the center of the rear wheel when the suspension is bumped. When the bump amount of the wheel suspension increases, the urging force to the elastic bush can be increased at a faster rate than the proportional relationship with respect to the increase in the bump amount. Similarly, if the shock absorber shaft center is configured to approach the center of the rear wheel at the time of rebound, the urging force to the elastic bush can be reduced at a rate that is steeper than the inverse proportion with respect to the increase in the rebound amount. Therefore, by doing so, it becomes possible to enhance the effect of the invention.

  Preferably, at least two of the five links are lower links, and the two lower links are arranged so as to approach each other toward the outer side of the vehicle as viewed from above the vehicle. That is, in the rear wheel suspension device, as described above, the elastic bushing of the rear wheel is urged in front of the vehicle body in advance by the vertical reaction force of the shock absorber, so that the braking force applied to the vehicle body during braking is reduced. Transmission may be delayed and brake feeling may deteriorate.

  On the other hand, in the present invention, the arrangement of the two lower links is such that a toe-in is geometrically given by the displacement of the rear wheel to the rear of the vehicle body at the time of braking. As a result, the brake force transmission delay due to the bending of the elastic bush described above can be compensated for, and deterioration of the brake feeling can be prevented.

  In addition, it is preferable that the toe-in amount of the rear wheel located outside the turn increases due to roll steer at the time of bumping and also increases due to compliance steer due to lateral force. In this configuration, the toe-in amount increases in accordance with the increase in the lateral force due to the roll steer and the lateral force compliance steer on the rear wheel outside the turning of the automobile, so that the behavior of the automobile during the turning can be stabilized.

  Preferably, a bump stopper that regulates the proximity displacement of the rear wheel with respect to the vehicle body is arranged coaxially with the shock absorber, and the moment force in the direction of the toe-in acting on the rear wheel is exerted by the vertical reaction force of the shock absorber. The buffer stopper is configured to increase as the reaction force of the shock absorber increases due to the action of the bump stopper.

  That is, in general, in order to stabilize the behavior of the automobile when turning, it is preferable to increase the toe-in amount of the rear wheel so that it is substantially proportional to the increase in lateral acceleration. If it changes, there is a possibility that a big change will occur in the behavior of the car at that time. However, when the bump stopper is provided, it is inevitable that the degree of increase in the toe-in amount due to, for example, roll steer is suddenly reduced by restricting the stroke of the suspension. This has been the cause of the unfavorable nature of many automobiles that cause the rear wheels to lose grip near the limit of lateral force when turning, leading to significant behavioral changes.

  On the other hand, when configured as described above, the coil spring of the shock absorber is compressed during the bump of the suspension, and the reaction force increases substantially in proportion to the lateral force, and the bump stopper provided coaxially therewith. As a result, the spring constant of the entire shock absorber increases further, the vertical reaction force of the shock absorber increases rapidly, and the moment force of the toe-in due to this reaction force increases synergistically. As a result, the sudden change in the toe-in amount due to the roll steer described above can be offset, the behavior change in the limit region of the automobile can be suppressed, and the running stability can be improved.

  Preferably, the end of the five links on the vehicle body side is attached to the subframe, and the subframe is attached to the vehicle body by a total of six elastic mounts, three on each of the left and right sides of the vehicle body. It is the composition which is done.

  In other words, the rear wheel suspension device for an automobile according to the present invention is a multi-link type device composed of five links, and a moment force in the direction of toe-in is applied to the rear wheels in advance using the vertical reaction force of the shock absorber. However, since the elastic bushing of each link is urged in a predetermined direction along with this, the ride comfort may be somewhat deteriorated.

  Therefore, all the five links are attached to the vehicle body via the subframe, and this subframe is attached to the vehicle body by a total of six elastic mounts, thereby improving the ride comfort without reducing the steering stability. Can do. That is, when compared with the more general four elastic mounts of the subframe, by using six elastic mounts, the shared load of the individual mounts is reduced correspondingly, and relatively soft mounts. Therefore, the vibration and the like are absorbed between the subframe and the vehicle body, and the riding comfort is improved. In this case, even if the entire sub-frame is displaced with respect to the vehicle body, all five links are attached to the sub-frame. It does not change and therefore has little adverse effect on handling stability.

  As described above, according to the rear wheel suspension device of an automobile according to the invention of the present application, in the multi-link type rear wheel suspension device including at least five links having elastic bushes at the end on the vehicle body side, The moment force in the direction of toe-in is applied to the rear wheel in advance by actively utilizing the vertical reaction force of the device, and the moment force in the direction of toe-in is directly applied to the rear wheel located outward during turning by a lateral force. Therefore, a sharp and natural driving feeling and a high stability feeling can be obtained while ensuring a good riding comfort through the elastic bushing.

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

  1 and 2 show an embodiment in which a rear wheel suspension apparatus A (hereinafter simply referred to as a rear suspension) according to the present invention is applied to rear wheels on both the left and right sides of the automobile, and the automobile of this embodiment is not shown. However, while the engine is mounted in the engine room at the front part of the vehicle body, the differential 1 (shown only in FIG. 2) is disposed at the rear part of the vehicle body to drive the rear wheel 2 (shown only on the right side of the vehicle body in FIG. 1). This is a rear-wheel drive vehicle. FIG. 1 is a perspective view of a rear suspension assembly composed of a pair of left and right rear suspensions A, A and a subframe 3 as viewed obliquely from the front right side of the vehicle body. FIG. 2 is a top view of the rear suspension assembly when a power transmission system such as a differential 1 is assembled. Reference numeral 4 denotes a propeller shaft that transmits rotational output from the transmission to the differential 1. Reference numerals 5 and 5 denote drive shafts for transmitting the rotational output from the differential 1 to the rear wheels 2 and 2.

  The suspension apparatus A of this embodiment is a multi-link type in which the wheel support 11 (support member) of the rear wheel 2 is connected to the vehicle body so as to be capable of stroke by five independent I links 6 to 10. Two upper links 6, 7 on the vehicle body front side and rear side constituting the upper arm, two lower links 8, 9 on the vehicle body front side and rear side constituting the lower arm, and the virtual upper arm and lower arm And a toe control link 10 for restricting the rotational displacement of the rear wheel 2 around the virtual kingpin axis K determined by the arrangement. The upper links 6 and 7 and the lower links 8 and 9 swing up and down around the end on the vehicle body side, so that the wheel support 11 and the rear wheel 2 stroke up and down along a predetermined locus. It has become.

  Further, a shock absorber 14 including a coil spring 12 and a damper 13 is disposed so as to allow an appropriate biasing force and damping force at the same time while allowing such a stroke of the rear wheel 2. In this shock absorber 14, the coil spring 12 and the damper 13 are arranged substantially coaxially and generally have a cylindrical shape that is long in the vertical direction, and a cylindrical bracket 15 disposed on the upper end side thereof is attached to a vehicle body (not shown). The lower end portion of the damper 13 (the lower end portion of the shock absorber 14) is pivotally attached to the vehicle body inner side of the wheel support 11. Accordingly, the reaction force of the coil spring 12 corresponding to the rearward load of the rear part of the vehicle body and the stroke of the rear wheel 2 (the vertical reaction force of the shock absorber) acts directly on the wheel support 11.

-Subframe configuration-
The sub-frame 3 is roughly composed of four steel plate members combined in a substantially rectangular frame shape in plan view, and front and rear cross members 17 and 18 extending in the vehicle width direction, and their left and right ends. It consists of a pair of side cross members 19 and 20 extending in the front-rear direction on both the left and right sides of the vehicle body so as to connect the parts. The front cross member 17 extends substantially straight in the vehicle width direction when viewed from above the vehicle body, and both end portions in the vehicle width direction are joined to the front end sides of the left and right side cross members 19 and 20, respectively. When viewed in the longitudinal direction of the vehicle body, the arch shape is largely curved so that the center portion in the longitudinal direction is located above the left and right end portions. Further, mounting seats (not shown) that project downward in the vicinity of the joints with the side cross members 19 and 20 are disposed on the left and right ends of the front cross member 17, respectively. The end of the toe control link 10 on the vehicle body side is attached to each.

  On the other hand, the rear cross member 18 extends substantially straight in the vehicle width direction when viewed from above the vehicle body, and both ends in the vehicle width direction are joined to the rear end sides of the left and right side cross members 19 and 20, respectively. In addition, when viewed in the longitudinal direction of the vehicle body, the length of the upper edge is an inverted trapezoid that is larger than the lower edge, and the rear lower link 9 extends downward from the left and right ends of the lower edge. , 9 are provided with attachment portions 18a, 18a for attaching end portions on the vehicle body side. Further, mounting seats 18b and 18b are disposed on the upper edge of the rear cross member 18 at positions corresponding to the mounting portions 18a and 18a of the rear lower link 9, and elastic mounting is provided on the mounting seats 18b. The differential 1 is suspended by a bracket 22 (shown only in FIG. 2) attached via 21.

  Further, the left and right side cross members 19 and 20 each bend gently so that the center portion in the longitudinal direction is located inward of the vehicle body as compared to the both end sides, and is substantially centered from the rear end portion in the vehicle body side view. The front part extends obliquely downward toward the front of the vehicle body, and the front part relative to the center is lower than the rear part. And the 1st attachment seats 19a and 20a are arrange | positioned in the front part of each side cross member 19 and 20 so that it may protrude below near the front side of the junction part with the front cross member 17. The end portions on the vehicle body side of the front lower link 8 are attached to the first attachment seats 19a and 20a, respectively, and the second attachment is provided so as to protrude upward in the vicinity of the rear side of the joint portion. Seats 19b and 20b are provided, and end portions on the vehicle body side of the front upper link 6 are attached to the second mounting seats 19b and 20b, respectively. On the other hand, third attachment seats 19c and 20c for attaching the end portions of the rear upper links 7 on the vehicle body side are disposed on the rear portions of the side cross members 19 and 20, respectively.

  Further, the side cross members 19 and 20 are provided with elastic mounts 23, 23,... For elastically supporting the entire sub frame 3 with respect to the vehicle body. And three points at the rear end. The substantially central elastic mount 23 is disposed on the upper surface of the mount mounting portion extending inward of the vehicle body from the substantially central portion of the side cross members 19 and 20, and is viewed from above the vehicle body. 23 and the elastic mount 23 at the rear end are positioned so as to be substantially parallel to a center line L (shown only in FIG. 2) in the front-rear direction of the vehicle body. On the other hand, the elastic mount 23 at the front end is located on the outer side of the vehicle body as compared with the elastic mounts 23 and 23 at the center and rear ends.

  In other words, the sub-frame 3 is connected to the vehicle body by a total of six elastic mounts 23, 23,... On each of the left and right sides of the vehicle body. The three elastic mounts 23, 23, 23 arranged at the rear end are arranged so as not to be aligned in a straight line in a plan view. When the sub-frame 3 is attached to the vehicle body by a total of six elastic mounts 23, 23,... In this way, the shared load of the individual elastic mounts 23 is reduced compared to the case of four general mounts. Since the characteristic can be made soft, the ride quality can be improved. Moreover, since the virtual plane is defined by the three elastic mounts 23, 23,... On both the left and right sides, the entire subframe 3 swings effectively when a lateral force is input to the rear wheel 2. , And the alignment change of the rear wheels 2, 2,.

  Reference numeral 24 shown in FIGS. 1 and 3 and the like is a reinforcing member that extends from the left and right ends of the front cross member 17 to the front portions of the side cross members 19 and 20, and reference numeral 25 denotes the reinforcing member. This is a reinforcing member constructed in a bracing manner from the lower end of the members 24, 24 to the lower edge of the rear cross member 18.

-Configuration of suspension device-
Next, with reference to FIGS. 3 to 5, the arrangement configuration of the links 6 to 10 of the suspension device A on the right side of the vehicle body will be described in detail. First, as seen from above the vehicle body, the front upper link 6 is connected to the second mounting seat 19b of the side cross member 19 through the rubber bush 26 (elastic bush) as shown in FIG. From there, the vehicle is extended rearwardly so as to be located rearwardly toward the outside of the vehicle body, and the end on the wheel side is connected to the wheel support 11 by a ball joint 27. The rear upper link 7 has substantially the same length as the front upper link 6, and an end of the vehicle body side is connected to the third mounting seat 19 c of the side cross member 19 via a rubber bush 26. As the vehicle heads outward from the vehicle body, it gradually tilts forward so as to be positioned forward, and the end on the wheel side is connected to the wheel support 11 by a ball joint 27.

  Further, the front lower link 8 is longer than the upper links 6 and 7, and an end on the vehicle body side is connected to the first mounting seat 19 a of the side cross member 19 via the rubber bush 26, while the end on the wheel side The portion is connected to the wheel support 11 by a ball joint 27, and is inclined rearward more greatly than the front upper link 6 as viewed from above the vehicle body. Further, the rear lower link 9 is longer than the front lower link 8, and the end of the vehicle body side is connected to the mounting portion 18a of the rear cross member 18 via the rubber bush 26, and from there to the outside of the vehicle body. The end of the wheel side is connected to the wheel support 11 by a ball joint 27.

  In other words, the two lower links 8 and 9 are arranged so as to approach each other toward the outer side of the vehicle body when viewed from above the vehicle body, and this arrangement causes the rear wheel 2 to move toward the rear of the vehicle body. A toe-in is applied geometrically with displacement (front-rear force compliance steer). That is, for example, when braking force from the road surface acts on the rear wheel 2 in the rear of the vehicle body, for example, during braking of an automobile, the two lower links 8 and 9 are each bent by the rubber bush 26 as schematically shown in FIG. As a result, it is slightly rotated around the end portion on the vehicle body side, so that the end portion on the wheel side is displaced rearward of the vehicle body. At this time, if the front lower link 8 is tilted rearward toward the vehicle body outward and the rear lower link 9 is tilted forward toward the vehicle body outward, a broken line is shown in the figure along with the rotational displacement of each link. As shown, the wheel side end portion of the front lower link 8 is displaced inward of the vehicle body, and the wheel side end portion of the rear lower link 9 is displaced outward of the vehicle body. It changes in the direction.

  In order to obtain the compliance steer as described above, it is not necessary to tilt the front link backward and the rear link forward as in this embodiment. What is necessary is just to arrange | position so that it may mutually approach, so that it goes to the vehicle body outer side. Alternatively, even when the two links are parallel, if the lengths thereof are made different, for example, if the front link is shorter than the rear link, it is possible to obtain a longitudinal force compliance steer in the toe-in direction. . Further, in the configuration of the above embodiment, the two upper links 6 and 7 are arranged in the same manner as the lower links 8 and 9, but the rubber bushes 26 and 26 of the upper links 6 and 7 are very different as will be described later. It is hard and its deflection is so small that compliance steer on the upper link side can be substantially ignored.

  As shown in FIG. 3, the toe control link 10 has an end on the vehicle body side connected to a mounting seat 17a of the front cross member 17 via a rubber bush 26 as viewed from above the vehicle body. The end on the wheel side is connected to the wheel support 11 by a ball joint 27. Further, as shown in FIG. 5, when viewed from the rear of the vehicle body, the upper links 6 and 7 are inclined slightly upward from the side cross member 19 toward the wheel support 11 outside the vehicle body. Further, the front lower link 8 is inclined slightly downward toward the outside of the vehicle body, and the rear lower link 9 and the toe control link 10 both extend substantially horizontally.

  The virtual kingpin axis K is the instantaneous center of rotation of the rear wheel 2 in the steering direction (toe direction), as seen from above the vehicle body as shown in FIG. This is an imaginary axis that passes through the intersection of the axes of the two upper links 6 and 7 and the intersection of the axes of the two lower links 8 and 9. In this embodiment, the virtual kingpin axis K of the rear wheel 2 is slightly rearwardly inclined so as to be located rearward of the vehicle body as seen from the side of the vehicle body as seen from the side of the vehicle body, and viewed in the longitudinal direction of the vehicle body. The upper end is slightly inclined so as to be located outward of the vehicle body (see FIG. 5).

  Further, the intersection k1 (see FIG. 4) with the road surface of the virtual kingpin axis K viewed from the side of the vehicle body is further away from the ground contact point G of the rear wheel 2 and the caster trail of the rear wheel 2 is negative. It has become. As a result, the lateral force acting on the ground contact point G with the road surface of the rear wheel 2 when the vehicle is turning crosses the front of the vehicle body of the virtual kingpin axis K, and this lateral force directly causes the toe-in to the rear wheel 2. Directional moment force acts. Thereby, the rubber bushes 26, 26 of the two lower links 6, 7 are mainly bent, and the toe-in amount of the wheel 2 is increased (lateral force compliance steer).

  That is, in the case of the rear suspension A of this embodiment, the toe-in amount of the left and right rear wheels 2 and 2 is increased by the longitudinal force compliance steer when braking the vehicle, and the toe-in of the rear wheel 2 outside the corner is turned when the vehicle is turning. The amount is increased by lateral force compliance steer. Although a detailed description is omitted, in the rear suspension A, the toe-in amount of the rear wheel 2 is increased by the roll steer at the time of bumping due to the arrangement configuration of the links 6 to 10.

  As shown in FIG. 3, the shock absorber 14 is disposed so as to vertically pass through the middle between the front links 6 and 8 and the rear links 7 and 9 when viewed from above the vehicle body, and its axis X is When viewed from the side of the vehicle body, it extends substantially vertically (see FIG. 4), and when viewed from the rear of the vehicle body, the upper end side is inclined so as to be located inside the vehicle body (see FIG. 5). In the upper end portion of the shock absorber 14, as shown by a broken line only in FIG. 4, the upper end portion of the rod 13a of the damper 13 is fixed to the upper end portion of the cylindrical bracket 15 via a rubber bush or the like. A cylindrical resin bump stopper 28 is disposed concentrically with the rod 13a so as to extend downward therefrom. The bump stopper 28 abuts against the upper end portion of the outer cylinder of the damper 13 when the coil spring 12 is contracted by a predetermined amount or more when the suspension device A is bumped. Therefore, the proximity displacement of the rear wheel 2 toward the vehicle body is restricted.

  The lower end portion of the bracket 15 of the shock absorber 14 is provided with an unusually shaped flange portion 29 that is long in the longitudinal direction of the vehicle body, and its upper surface is joined and fastened to the lower frame of the vehicle body. . On the other hand, an upper sheet for holding the upper end portion of the coil spring 12 is formed on the lower surface of the flange portion 29, and the lower end portion of the coil spring 12 disposed so as to surround the outer cylinder of the damper 13 is the lower end of the outer cylinder of the damper 13. It is held by a lower sheet portion 13b provided on the side. Further, an annular mounting portion 13 c is projected from the lower end portion of the damper 13, and is pivotally attached to the end portion of the connecting portion 30 that extends from the wheel support 11 of the rear wheel 2 to the inside of the vehicle body.

  Specifically, the connecting portion 30 of the wheel support 11 is integrally formed inside the main body of the wheel support 11 through which the axle of the rear wheel 2 passes, and when viewed in the vehicle longitudinal direction as shown in FIG. An upper arm portion 31 and a lower arm portion 32 that extend from the upper and lower end sides of the wheel support 11 body toward the inside of the vehicle body and are integrated at the front end portion, and the upper arm portion 31 and the lower arm portion 32 are respectively intermediate in the vehicle width direction. It has an intermediate arm portion 33 extending in the vertical direction so as to be connected at the portion, and has a substantially A-shape in the horizontal direction as a whole. Then, from the intermediate arm portion 33 that is the A-shaped horizontal bar to the tip portions of the upper arm portion 31 and the lower arm portion 32 that are the upper ends of the A shape (tip portions inside the vehicle body of the connecting portion 30). The support shaft 34 is disposed, and the end of the support shaft 34 protrudes inward of the vehicle body from the end of the connecting portion 30, and is inserted into the lower end mounting portion 13 c of the damper 13. It is fixed through. Thus, by making the connecting part 30 substantially A-shaped, the weight of the connecting part 30 and thus the wheel support 11 as a whole can be reduced while securing sufficient rigidity against the load in the vertical direction. The increase in unsprung weight due to the provision of the can be suppressed, and deterioration of the exercise performance can be prevented.

  By attaching the upper end of the shock absorber 14 to the lower frame of the vehicle body via the bracket 15 as described above, most of the force input from the rear wheel 2 to the shock absorber 14 is only transmitted to the lower frame of the vehicle body. And hardly transmitted to the upper part of the vehicle body. Therefore, in order to ensure the rigidity of the vehicle body, it is only necessary to reinforce the lower frame, which improves the degree of freedom in designing the automobile. Further, the load sharing at the rear of the vehicle body and the vertical reaction force of the shock absorber 14 directly act on the rear wheel 2 via the connecting portion 30 of the wheel support 11, but as described above, the A-shaped horizontal bar ( Since the lower end portion of the damper 13 is attached to the support shaft 34 attached at two points with a sufficiently large distance from the intermediate arm portion 33) to the tip end portion, the vertical reaction force of the shock absorber 14 is ensured. Be transmitted.

  The main feature of the present invention is to optimize the alignment of the rear wheel 2 by urging the wheel support 11 in a predetermined direction in advance using the reaction force acting from the shock absorber 14 as described above. Further, the rubber bushes 26, 26,... Of the links 6 to 10 are respectively given an urging force in an optimum direction, that is, the rubber bushes 26 are pre-compressed in an optimum direction by the vertical reaction force of the shock absorber 14. In the multi-link type suspension, a sharp driving sensation applicable to a sports car can be obtained. Specifically, due to the vertical reaction force of the shock absorber 14, 1) a moment force in the direction of the negative camber is applied to the rear wheel 2 so as to overcome the lateral force during turning, and 2) during turning A moment force in the direction of toe-in is applied before the lateral force acts, and 3) A biasing force in the front of the vehicle body is applied to the rubber bushes 26 and 26 of the lower links 8 and 9 that have a particularly large influence on the ride comfort. Like to do.

  Hereinafter, each of the three characteristic points will be described. First, as schematically shown in FIG. 7, when the rear suspension A on the right side of the vehicle body is viewed from the rear, the shock absorber 14 is arranged in the direction of its axis X. The reaction force Fc causes the rear wheel 2 to generate a sufficiently large moment force Mn in the direction of the negative camber via the wheel support 11, in other words, the length of the arm of the moment force Mn due to the vertical reaction force of the shock absorber 14. Is arranged relatively far away from the inside of the vehicle body so as to be sufficiently large. Specifically, for example, the length d (the length of the arm of the moment force Mn of the negative camber due to the reaction force of the shock absorber 14) of the perpendicular line dropped from the center C of the rear wheel 2 to the axis X of the shock absorber 14 is set. It is preferable that the ratio be equal to or larger than a predetermined ratio set in advance with respect to the radius D of the rear wheel 2 (the arm length of the moment force Mp of the positive camber due to the lateral force).

  Here, the setting of the predetermined ratio will be described. First, the magnitude of the moment force Mn in the direction of the negative camber acting on the rear wheel 2 by the vertical reaction force Fc of the shock absorber 14 depends on the axis of the shock absorber 14. It is expressed as the product of the distance from the center X to the rear wheel center C (the length of the moment arm) and the shock absorber reaction force Fc. However, in general, in the rear suspension A of an automobile, a shared load and a buffer on the rear wheel 2 outside the turn are obtained so as to obtain a target turning performance of the automobile, for example, a maximum target lateral acceleration during turning. The hardness of the coil spring 12 of the device 14, the maximum grip force of the rear wheel 2, and the like are set, so that the shock absorber reaction force Fc itself is generally determined.

  Therefore, in order to increase the moment force Mn in the negative camber direction sufficiently, it is necessary to substantially increase the length of the arm of the moment. For example, assuming a limit region in which the maximum lateral acceleration is generated in the rear wheel when the vehicle is turning, the shock absorber reaction is less than the moment force Mp of the positive camber acting on the rear wheel 2 by the limit lateral force Fs at that time. The length of the arm of the moment may be set so that the moment force Mn of the negative camber due to the force Fc increases. In other words, the arm length d and the moment Mp of the moment force Mn are set so that the moment force Mn of the negative camber acting on the rear wheel 2 in the limit region of the lateral force Fs is larger than the moment force Mp of the positive camber. The ratio with the arm length D may be set by experiment or the like.

  More specifically, generally, a moment force Mp in the direction of the positive camber acts directly on the rear wheel 2 outside the turn by the lateral force Fs when the vehicle is turning, and this moment force Mp increases with the lateral force Fs. On the other hand, when the moment force Mn in the negative camber direction is applied to the rear wheel 2 by the vertical reaction force Fc of the shock absorber 14 as described above, when the lateral acceleration increases and the roll of the vehicle body increases when the vehicle turns, The reaction force Fc increases as the coil spring 12 of the shock absorber 14 is compressed, and the moment force Mn of the negative camber due to the reaction force Fc also increases.

  Accordingly, the shock absorber 14 is disposed as in this embodiment, and the initial value of the moment force Mn of the negative camber due to the vertical reaction force Fc of the shock absorber 14 (when the vehicle is stopped or traveling straight at a constant speed). If the positive camber moment force Mp due to the lateral force Fs increases at the time of turning, the negative camber moment force Mn that overcomes this will be reduced to the lateral force limit region of the rear wheel 2. It can be generated. Thus, in the rear wheel 2 outside the turn, the direction of the camber change, that is, the lateral direction of the vehicle body in the rubber bushes 26, 26,. Thus, a biasing force in a certain direction is applied (pre-compression), thereby eliminating the microscopic wobbling of the rear wheel 2 and obtaining a sharp driving feeling.

  Secondly, in the rear suspension A of this embodiment, as shown in FIG. 4, the axis X of the shock absorber 14 is set with respect to the virtual kingpin axis K of the rear wheel 2 slightly tilted backward as viewed from the side of the vehicle body. The shock absorber axis X is positioned so as to extend substantially in the vertical direction, and is positioned so as to be non-parallel to the virtual kingpin axis K and not to intersect with the virtual kingpin axis K (see FIG. 5) inward of the virtual kingpin axis K. . Thus, when the rear wheel 2 on the right side of the vehicle body is viewed from above the vehicle body as schematically shown in FIG. 8, the vertical reaction force Fc of the shock absorber 14 is counterclockwise moment force around the virtual kingpin axis K, that is, A moment force Mt in the toe-in direction is generated. In other words, the vertical reaction force of the shock absorber 14 is used to urge the wheels 2 and 2 in the direction of toe-in after the lateral acceleration or posture change occurs in the vehicle (initial state). When a toe-in is applied by applying a lateral force to the rear wheel 2 at the beginning of turning, a delay due to the bending of the rubber bushes 26, 26,... Of the links 6 to 10 does not occur. A sharp driving feeling with high rigidity and responsiveness can be obtained.

  Third, in the rear suspension A of this embodiment, as schematically shown in FIG. 9, the shock absorber 14 has a shaft center X at the rear side of the rear wheel 2 relative to the center C of the rear wheel 2 at the inner side of the rear wheel 2. And is arranged so as to extend in a substantially vertical direction. Thus, as shown in the figure, when viewed from the left side of the vehicle body, the vertical reaction force Fc of the shock absorber 14 acts on the wheel support 11 from the substantially vertical upper side behind the center C of the rear wheel 2 (right side in the figure). A clockwise moment force Mw is generated. As a result, the upper links 6 and 7 are urged to the rear of the vehicle body, and the urging force to the rear of the vehicle body acts on the rubber bushes 26 and 26 of the links 6 and 7, respectively. The urging force toward the front of the vehicle body acts on the rubber bushes 26, 26 of the links 8, 9 respectively.

  Thus, the rubber bushes 26 and 26 of the upper links 6 and 7 are all extremely hard, while the rubber bush 26 of the lower links 8 and 9 is relatively soft. That is, the rubber bush 26 is made relatively soft for each of the lower links 8 and 9 that have a relatively great influence on the ride comfort, and the rubber bush 26 is pre-compressed ahead of the vehicle body by the vertical reaction force of the shock absorber 14. It is doing. In this state, the rubber bush 26 has almost no allowance for bending forward of the vehicle body, so that when the force (for example, driving force) forward of the vehicle body acts on the rear wheel 2, the rubber bush 26 hardly bends. The transmission of force to the vehicle body is performed.

  On the other hand, when a force (for example, shock from an irregular road surface) is input to the rear wheel 2 with the rubber bush 26 pre-compressed in front of the vehicle body as described above, the input acts on the rubber bush 26 by this input. When the force to be applied becomes larger than the urging force and the direction of the resultant force is reversed, the rubber bush 26 is bent backwards, contrary to the initial state, and the rear wheel 2 is displaced rearward of the vehicle body. In other words, the backward input is delayed or absorbed from the rear wheel 2 to the vehicle body.

-Effect-
Next, the operation and effect of the rear suspension A of the present embodiment configured as described above will be described. First, when the automobile is stopped or goes straight at a constant speed, the left and right rear suspensions A, A The force corresponding to the shared load at the rear of the vehicle body acts on the wheel support 11 of the rear wheel 2 from the shock absorber 14, and the moment force in the negative camber direction and the toe-in direction acts on the rear wheel 2. Yes (initial state). When the driver is steered in the vehicle that is traveling straight, a lateral force is generated on the front wheel and the rear wheel of the vehicle and the vehicle is turned to the turning state. At this time, the lateral force is applied to the rear wheel 2 outside the turning. A toe-in is given by the above, and a toe-in is also given by a roll of the vehicle body with a slight delay. As a result, the behavior of the automobile is stabilized.

  At this time, since the rear wheel 2 is urged in the negative camber and toe-in direction in advance even in the straight traveling state, the rubber bushes 26 and 26 of the links 6 to 10 are applied when the toe-in is applied to the rear wheel 2 by a lateral force or a roll. ,... Will not cause a delay, and a multi-link suspension has a sense of rigidity that is unparalleled in the past and a sharp driving feeling with little phase delay. Moreover, since the rear wheels 2 outside the turning of the automobile are consistently biased in the negative camber and toe-in directions from the straight running state to the beginning of turning, a natural driving feeling and high stability can be obtained. .

  Subsequently, when the lateral acceleration of the turning vehicle increases and the lateral force acting on the rear wheel 2 increases, the toe-in amount due to the lateral force and roll steer increases, and the bump amount of the rear suspension A increases. The reaction force of the shock absorber 14, that is, the coil spring 12 is increased approximately proportionally, and the moment force in the direction of the toe-in is thereby increased. When the bump amount is further increased and the upper end portion of the outer cylinder of the damper 13 comes into contact with the bump stopper 28, the spring constant of the shock absorber 14 as a whole is further increased, and the reaction force of the shock absorber 14 increases rapidly. Thus, the moment force in the direction of the toe-in increases synergistically. As a result, even if the amount of toe-in due to roll steer decreases suddenly due to the action of the bump stopper 28, this is offset by a sudden increase in the moment force of toe-in due to the reaction force of the shock absorber 14. Since the toe-in amount of the wheel 2 does not change suddenly, it is possible to suppress the behavior change in the limit region of the automobile and improve the running stability.

  Further, as the lateral acceleration increases during the turning, the moment force in the direction of the positive camber acting on the rear wheel 2 due to the lateral force increases, but the vertical reaction force of the shock absorber 14 also increases as the lateral acceleration increases. As a result, the moment force in the direction of the negative camber acts on the rear wheel 2 outside the turn to the limit region of the lateral force. That is, an urging force of a constant direction always acts on the rubber bushes 26, 26,... Of the links 6 to 10 of the rear wheel 2 outside the turning, in the direction of camber change, that is, in the lateral direction of the vehicle body. Since the microscopic wobbling of the rear wheel 2 does not occur, an unprecedented sharp driving feeling can be obtained as a multi-link suspension.

  In this regard, the rubber bushes 26 of the suspension links 6 to 10 on the rear wheels 2 outside the turn until the vehicle speed is gradually increased while the steering angle of the vehicle is kept substantially constant and the vicinity of the grip limit is reached. The experimental results obtained by measuring the urging force acting on each of 26,. First, the graph of FIG. 10 shows (a) a change in vehicle speed and (b) a change in lateral acceleration with respect to the passage of time. In this experiment, the vehicle speed was increased relatively abruptly, and thereafter Slightly increased to the specified vehicle speed. At this time, the lateral acceleration also rises relatively fast in response to the increase in vehicle speed, and then rises moderately, reaching the grip limit of the rear wheel 2 at about 0.8 G (gravity acceleration). Yes.

  Corresponding to such changes in vehicle speed and lateral acceleration, the front upper link 6, the rear upper link 7, the front lower link 8, the rear lower link 9 and the toe control link 10 are respectively shown in the graphs of FIGS. The urging force acting on each rubber bush 26 changes. That is, as shown in FIG. 11 (a), the front upper link 6 is negative in the lateral direction in the initial state, that is, an urging force of about 200 N toward the outside of the vehicle body is acting. When the acceleration increases, the absolute value of the urging force temporarily increases and then increases to about 1600 N outside the vehicle body near the grip limit. Further, as shown in FIG. 5B, the urging force in the front-rear direction is substantially zero in the initial state, and increases toward the rear of the vehicle body as the vehicle speed and lateral acceleration increase.

  In the case of the rear upper link 7 shown in FIG. 12, in the initial state, an extremely large urging force of 3000 N or more acts inward in the lateral direction and an urging force of about 100 N acts on the rear side of the vehicle. is doing. As the vehicle speed and lateral acceleration increase, the lateral urging force decreases and becomes approximately 1900 N inward of the vehicle body near the grip limit.

  Similarly, in the front lower link 8 shown in FIG. 13, an urging force of about 800 N acts on the vehicle body inward in the lateral direction in the initial state, and an urging force of about 2.5 N acts on the front of the vehicle body. As the vehicle speed and lateral acceleration increase, the lateral urging force increases to approximately 2300 N inward of the vehicle body near the grip limit. Further, in the rear lower link 9 shown in FIG. 14, an urging force of about 4000 N acts on the outer side of the vehicle in the lateral direction in the initial state, and an urging force of about 25 N acts on the front of the vehicle, As the vehicle speed and lateral acceleration increase, the lateral urging force decreases and becomes substantially zero near the grip limit.

  Considering the above experimental results, in the initial state, the moment force Mn in the direction of the negative camber acts on the wheel support 11 by the vertical reaction force of the shock absorber 14 (see FIG. 7), and clockwise when viewed from the left side of the vehicle body Moment force Mw is acting (see FIG. 9), and the moment force Mn in the camber direction is mainly received by the rear upper and lower links 7, 9 close to the point of action of the shock absorber 14 reaction force. Therefore, a compression axial force acts on the rear upper link 7 and a tensile axial force acts on the rear lower link 9. Moreover, in the rear links 7 and 9, the moment force Mw also becomes an axial force of compression and tension, respectively. As a result, a very large compressive force acts on the rear upper link 7 in the axial direction. A very large urging force (3000 N or more) is applied to the rubber bush 26 toward the inside of the vehicle body in the lateral direction. Further, a very large tensile force acts on the lower lower link 9 in the axial direction, and a very large urging force (about 4000 N) acting on the rubber bush 26 toward the outside of the vehicle body acts on the rubber bush 26 in the lateral direction. Become.

  On the other hand, in the front links 6 and 8 that have a greater degree of inclination in the front-rear direction than the rear links 7 and 9, the influence of the moment force Mn in the camber direction is reduced, and two moment forces Mn, Mw acts in the opposite direction in the axial direction to cancel each other. As a result, a relatively small tensile force acts on the front upper link 6 in the axial direction, and a relatively small urging force (about 200 N) acting on the outer side of the vehicle body acts on the rubber bush 26 in the lateral direction. The urging force for the direction is substantially zero. A relatively small compressive force acts on the front lower link 8 in the axial direction, and an urging force (about 800 N) directed inward of the vehicle body acts on the rubber bush 26 in the lateral direction. Only a slight urging force (about 2.5 N) is applied.

  When the vehicle speed and lateral acceleration increase during turning of the automobile, the urging force of each rubber bush 26, 26,... Changes accordingly as shown in the experimental data. In each of the rubber bushes 26, 26,... Of the four links 6 to 9, the lateral biasing force does not cross the origin (0), and is always the same from the initial state to the limit region of the lateral force of the rear wheel 2. Acts in the direction. From this, it can be seen that in the rear suspension A of the automobile used in the experiment, the rear wheels 2 and 2 are always urged in the negative camber direction to the vicinity of the grip limit while the automobile is turning. .

  For the toe control link 10, as shown in the graph of FIG. 15, an urging force of about 300 N is applied in the lateral direction toward the inside of the vehicle body in the initial state, and the urging force in the longitudinal direction of the vehicle body is substantially zero. As the vehicle speed and lateral acceleration increase, the lateral urging force increases to approximately 1000 N inward of the vehicle body near the grip limit. From this, it is understood that the urging force in the direction of the toe-in acts on the rear wheel 2 from the initial state to the vicinity of the grip limit.

  Further, in the rear suspension A of this embodiment, the rubber bushes of the front and rear lower links 8 and 9 that have a particularly great influence on the riding comfort among the five links 6 to 10 are made relatively soft. As is apparent from the experimental data, the rubber bushes 26, 26 of the two lower links 8, 9 are given a weak urging force to the front of the vehicle body in the initial state by the vertical reaction force of the shock absorber 14. ing. As a result, even when a shock due to road surface irregularities (impact force toward the rear of the vehicle body) is input to the rear wheel 2 while the vehicle is running, the shock is absorbed by the bending of the rubber bushes 26 and 26, and the riding comfort is good. Can be obtained. Moreover, as is apparent from the graphs of FIGS. 13 and 14, the urging forces acting on the rubber bushes 26 and 26 of the lower links 8 and 9 in the initial state are both small, and particularly the front lower link 8 having a great influence on the ride comfort. Since only a small urging force (about 2.5 N) is acting on the, the urging force does not hinder the bending of the rubber bush 26, and shock absorption is performed extremely effectively.

  In addition, since the rubber bushes 26 and 26 of the relatively soft lower links 8 and 9 are pre-compressed to the front of the vehicle body in the initial state as described above, for example, when a driving force acts on the rear wheel 2 during acceleration of the automobile, The bending allowance remaining in the rubber bushing 26 is small, and the transmission delay of the force to the vehicle body is reduced, and the acceleration response of the automobile to the accelerator operation is sufficiently increased. In addition, during acceleration, the urging force to the rubber bush 26 increases as the vehicle accelerates due to the squat of the vehicle body, so that a high acceleration response can be obtained without delay even for a large driving force.

  On the contrary, when the vehicle is braked, the transmission of the braking force from the rear wheel 2 to the vehicle body is delayed due to the bending of the rubber bush 26. However, during braking, the rebound amount of the rear suspension A increases and the vertical reaction force of the shock absorber 14 increases. And the urging force to the rubber bush 26 is reduced, so that the direction of the bending is reversed relatively quickly. In this embodiment, the toe-in of the rear wheel 2 is caused by the longitudinal force compliance steering during braking. Since the amount of the braking force is increased to accelerate the generation of the braking force with the road surface, even if the transmission of the braking force to the vehicle body is delayed due to the bending of the rubber bush 26, the braking force of the vehicle as a whole is increased. The start-up delay is negligible and the brake feeling is not substantially deteriorated.

  Furthermore, in this embodiment, the rear suspensions A and A having the above-described configuration are attached to the vehicle body by a subframe 3 via a total of six elastic mounts 23, 23,. By making the mount 23 have a soft characteristic, the ride comfort can be further improved. Moreover, even if the entire sub-frame 3 is displaced with respect to the vehicle body, this does not change the mutual positional relationship of the suspension links 6 to 10 or the positional relationship with respect to the road surface, so there is almost no adverse effect on steering stability. Absent.

(Other embodiments)
In addition, the structure of this invention is not limited to the thing of the said embodiment, Various other structures are included. That is, in the above-described embodiment, the left and right rear suspensions A and A are attached to the vehicle body by the subframe 3. However, the present invention is not limited to this, and the rear suspensions A and A may be directly attached to the vehicle body.

  Further, in the rear suspension A of the above-described embodiment, the rubber bush 26 is disposed at the vehicle body side connection portion of each of the five links 6 to 10, while the wheel side end portion is connected to the wheel via the ball joint 27. Although it is made to attach to the support 11, it is not restricted to this, You may make it arrange | position rubber bushs to the both ends of either link, respectively. Further, the elastic bushing is not limited to the rubber bushing 26 and may be made of resin having a required elasticity.

1 is a perspective view of a rear suspension assembly of an automobile to which a rear wheel suspension device of an automobile according to the present invention is applied. It is a top view of the rear suspension assembly to which a power transmission system path is attached. It is a top view of the rear suspension on the right side of the vehicle body. FIG. 4 is a left side view of the rear suspension of FIG. 3. FIG. 4 is a rear view of the rear suspension of FIG. 3. It is explanatory drawing of the longitudinal force compliance steer by arrangement | positioning of a lower link. It is explanatory drawing of the moment force of the direction of a negative camber by the vertical reaction force of a buffering device. It is explanatory drawing of the moment force of the direction of toe-in by the vertical reaction force of a buffering device. It is explanatory drawing of the moment force around the axle shaft by the vertical reaction force of the shock absorber. FIG. 4 is a graph showing (a) change in vehicle speed and (b) change in lateral acceleration over time in a turning test of an automobile. It is a graph which shows the change of the force of (a) lateral direction and (b) front-back direction which acts on the rubber bush of a front side upper link in the turning test of a motor vehicle. FIG. 12 is a view corresponding to FIG. 11 for the rear upper link. FIG. 12 is a view corresponding to FIG. 11 for the front lower link. FIG. 12 is a view corresponding to FIG. 11 for the rear lower link. FIG. 12 is a view corresponding to FIG. 11 for a toe control link.

Explanation of symbols

A Rear suspension (rear wheel suspension device)
K virtual kingpin shaft X axis of shock absorber 2 rear wheel 3 subframe 6, 7 upper link 8, 9 lower link 10 toe control link 11 wheel support (supporting member)
12 Coil spring 13 Damper 14 Shock absorber 23 Elastic mount 26 Rubber bush (elastic bush)
28 Bump stopper 30 Wheel support connecting portion 31 Upper arm portion 32 Lower arm portion 33 Intermediate arm portion 34 Support shaft

Claims (2)

The support member of the rear wheel of the automobile is connected to the vehicle body by five links, and an elastic bush is provided at least at the end of the vehicle body side of each link, and the upper end side of the shock absorber that generates the vertical reaction force In the multi-link type rear wheel suspension device in which the lower end is pivotally attached to the vehicle body inward side of the rear wheel support member,
The rear wheel's virtual kingpin shaft is set so that the moment force in the toe-in direction is generated around the virtual kingpin shaft by the vertical reaction force of the shock absorber, and the caster rail is set to a negative value. A rear wheel suspension device for an automobile. In claim 1,
A rear wheel suspension device for an automobile, wherein the rear wheel virtual kingpin shaft is set to be tilted rearward so that the upper end side of the rear wheel is positioned rearward of the vehicle body when viewed from the side of the vehicle body.

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