JP5056235B2 - Suspension device for auxiliary steering wheel for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension device of an auxiliary steered wheel for a vehicle in which demanded driving force of an actuator to steer the auxiliary steered wheel has small suspension geometry. <P>SOLUTION: A first lower link member 3 and a second lower link member 4 are arranged on this suspension device so that a caster trail &epsi;<SB>0</SB>between a grounding point of a king pin axis Kp connecting a virtual pivot point 0 provided by the first lower link member 3 and the second lower link member 4 and an axle member side mounting point of an upper arm member to each other and an auxiliary steered wheel rotating center as seen from the side of the vehicle becomes the same as the occurrence probability maximum pneumatic trail occurring most frequently under and in a common-sense and general travelling condition and travelling state. Consequently, the king pin axis Kp passes through a point of application of lateral force in the travelling state and under the travelling condition occurring most frequently where the pneumatic trail becomes the occurrence probability maximum pneumatic trail, and it is possible to minimize the demanded driving force of the auxiliary steered wheel steering actuator. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a suspension device for a vehicle auxiliary steering wheel for suspending the auxiliary steering wheel so as to be vertically displaceable (suspension stroke is possible) with respect to a vehicle body.

In order to improve vehicle steering responsiveness and steering stability, and improve vehicle turning performance at low vehicle speeds, the rear wheels are slightly angled in the same or opposite phase when turning the front wheels, which are the main steering wheels. The technology to steer only is known and is used in some vehicles.
As a suspension device for suspending a rear wheel (sub-steering wheel) on a vehicle body in a four-wheel steering vehicle that also steers the rear wheel as described above, a rear suspension device as described in Patent Document 1, for example, is conventionally known. It has been.

This vehicle auxiliary steering wheel suspension system uses a number of I-type link members to suspend a rear wheel (sub-steering wheel) from the vehicle body so that the rear wheel (sub-steering wheel) can be steered. Suspension device.
JP 2005-096552 A

  However, conventional suspension devices for vehicular auxiliary steering wheels represented by the above do not take into account the driving force of the actuator required when turning the auxiliary steering wheels, causing the following problems. It was.

  In other words, there is a limit to the output possible driving force of the actuator that steers the auxiliary steering wheel due to restrictions on the installation space of the actuator, etc., and there is no consideration for reducing the required driving force of the actuator. In the case of a vehicle using a suspension device, the problem arises that the sub-steering wheel cannot be steered as required under all conditions where the steering of the sub-steering wheel is required.

  In view of the above situation, the present invention can turn the auxiliary steering wheel as required under all conditions where the steering of the auxiliary steering wheel is required even with the limited output possible driving force of the actuator. An object of the present invention is to propose a suspension device for a sub-steering wheel that has been devised to reduce the required driving force of an actuator, thereby eliminating the problems of the conventional device.

To this end, the vehicle auxiliary steering wheel suspension device according to the present invention is constructed as described in claim 1.
First, the suspension device which is the premise of the present invention is:
An axle member having a shaft portion that rotatably supports the auxiliary steering wheel is suspended from the vehicle body in a manner that can be displaced in the vehicle vertical direction by a plurality of links extending inward in the vehicle width direction from the axle member. is there.

The present invention, as the plurality of links constituting such a suspension device for a vehicle auxiliary steering wheel,
An upper arm member extending between a position above the axle portion of the axle member and the vehicle body;
Three first lower link member extending between the lower portion and the vehicle body than the shaft portion of the axle member, and a second lower link member and the third lower link member is provided,
When viewed from the side of the vehicle, the first lower link member and the virtual pivot point provided by the first lower link member and the second lower link member are located rearward of the axle member side attachment point of the upper arm member and Arranging the second lower link member; and
Similarly, when viewed from the side of the vehicle, a caster rail between a grounding point of the kingpin axis connecting the virtual pivot point and the attachment point on the axle member side of the upper arm member and a grounding point of a vertical line passing through the center of the auxiliary steering wheel. The first lower link member and the second lower link member are arranged so as to be the same as the occurrence probability maximum pneumatic trail having the highest occurrence probability density with respect to the pneumatic trail of the auxiliary steering wheel ,
The third lower link member is characterized in that the vehicle body side attachment point far from the axle member is connected to a steering actuator so as to control the steering wheel .

In the vehicle auxiliary steering wheel suspension apparatus of the present invention,
To arrange the first lower link member and the second lower link member that suspend the axle member on the vehicle body in cooperation with the upper arm member as follows,
That is, when viewed from the side of the vehicle, the first lower link is such that the virtual pivot point provided by the first lower link member and the second lower link member is located behind the axle member attachment point of the upper arm member. Arranging the member and the second lower link member; and
Similarly, when viewed from the side of the vehicle, a caster rail between a grounding point of the kingpin axis connecting the virtual pivot point and the attachment point on the axle member side of the upper arm member and a grounding point of a vertical line passing through the center of the auxiliary steering wheel. In order to arrange the first lower link member and the second lower link member so as to be the same as the maximum occurrence probability pneumatic trail having the highest occurrence probability density with respect to the pneumatic trail of the auxiliary steering wheel,
Under the most frequently occurring driving conditions and conditions where the pneumatic trail of the secondary steering wheel is the maximum probability of occurrence, the kingpin axis of the secondary steering wheel will pass the lateral force point, and the steering actuator will it is possible to reduce the required driving force of the steering actuator required when 3 via the lower link member to steer the sub steering wheel.

Therefore, even with the limited output possible driving force of the actuator, the sub steered wheels can be steered as required under all conditions where the steered wheels are required to be steered.
The vehicle steering response improvement effect, the steering stability improvement effect, and the small turning performance improvement effect at low vehicle speeds can always be achieved as intended by turning the auxiliary steering wheel.

Hereinafter, embodiments of the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 shows a vehicle auxiliary steering wheel suspension apparatus according to an embodiment of the present invention, W _L is a left auxiliary steering wheel (left rear wheel), W _R is a right auxiliary steering wheel (right rear wheel), These left and right auxiliary steered wheels W _L and W _R are rotatably supported by shaft portions (not shown) of the respective axle members 1 and are provided by a plurality of links extending inward in the vehicle width direction from these left and right axle members 1. Suspended from a vehicle body (not shown) so as to be displaceable in the vertical direction of the vehicle (suspension stroke is possible).

Hereinafter, the plurality of links will be described in detail, and the suspension structure of the axle member 1 using these links will be described in detail.
The plurality of links include an upper arm member 2 that extends above the auxiliary steering wheel support shaft portion of the axle member 1 and between the vehicle body, and
Three first lower link members 3, a second lower link member 4, and a third lower link for turning the auxiliary steering wheel, which extend below the auxiliary steering wheel support shaft portion of the axle member 1 and between the vehicle bodies. It shall consist of the member 5.

The upper arm member 2 is an A-type arm, and is disposed so that the bifurcated base ends 2a and 2b are positioned in the vehicle front-rear direction and the front end 2c is directed outward in the vehicle width direction.
The bifurcated base ends 2a and 2b of the upper arm member 2 are attached to the vehicle body through an elastic bush so as to be swingable in the vertical direction, and provide a vehicle body side attachment point of the upper arm member 2.
The tip 2c of the upper arm member 2 is connected to the upper end of the rod 6 provided to extend upward from the axle member 1 via a joint, and between the tip 2c of the upper arm member 2 and the upper end of the rod 6 The joint node is an attachment point of the upper arm member 2 on the axle member side.

As described above, the first lower link member 3 extends inward in the vehicle width direction from the axle member 1, but at this time, the first lower link member 3 is directed to extend forward of the vehicle.
And the extending direction front-end | tip 3a of the 1st lower link member 3 shall be attached to a vehicle body so that a rocking | fluctuation to an up-down direction is possible via an elastic bush, and shall provide a vehicle body side attachment point.
The end portion 3b on the opposite side of the first lower link member 3 is articulated via an elastic bush at the tip of a rod 7 provided to extend downward from the axle member 1, and the end portions of these first lower link members 3 The joint node between 3b and the tip of the rod 7 is the axle member side attachment point of the first lower link member 3.

The second lower link member 4 is arranged behind the first lower link member 3 in the vehicle.
The second lower link member 4 extends from the axle member 1 inward in the vehicle width direction as described above, and the extending direction tip 4a is attached to the vehicle body so as to be vertically swingable via an elastic bush. Suppose that the attachment point on the vehicle body side is provided.
The end portion 4b on the opposite side of the second lower link member 4 is articulated via an elastic bush at the tip of a rod 8 provided to extend downward from the axle member 1, and the end portions of these second lower link members 4 A joint node between 4b and the tip of the rod 8 is an attachment point on the axle member side of the second lower link member 4.

As described above, the third lower link member 5 for turning the sub-steering wheel extends from the axle member 1 inward in the vehicle width direction, and the extending direction tip 5a meshes with the pinion 11a of the rear wheel steering actuator 11. The rack is connected to both ends of a steering member (not shown) such as a rack via bushes, and is attached to the vehicle body through the steering member so as to be swingable in the vertical direction.
Therefore, the tip 5a of the third lower link member 5 serves as a vehicle body side attachment point of the third lower link member 5.
An end portion 5b on the opposite side of the third lower link member 5 is articulated via a bush to the tip of a rod 9 provided to extend rearward from the axle member 1, and the end portions of the third lower link member 5 The joint node between 5b and the tip of the rod 9 is the attachment point on the axle member side of the third lower link member 5.

  Thus, when the actuator 11 is actuated to rotate the pinion 11a, the left and right auxiliary steered wheels ( The left and right rear wheels can be steered in the same direction.

  With the suspension link structure described above, the axle member 1 is suspended so as to be able to move in the vertical direction of the vehicle together with the left and right auxiliary steering wheels rotatably supported by these, and the vertical vibration of the axle member 1 (left and right auxiliary steering wheels) in the stroke direction is suspended. A shock absorber 10 for damping is installed between the vehicle body and the suspension link structure.

In the present embodiment, as shown in FIG. 2, the first lower link member 3 extends from the axle member 1 inward in the vehicle width direction and the vehicle front, and the second lower link member 4 extends from the axle member 1 in the vehicle width direction. In this case, the virtual pivot point O of the lower link mechanism provided by the first lower link member 3 and the second lower link member 4 as shown in FIGS. As shown in FIG. 4 when viewed from the side, the first lower link member 3 and the second lower link member 4 are arranged so as to be located behind the axle member side attachment point 2c of the upper arm member 2,
Accordingly, as shown in FIG. 4, the kingpin axis Kp set to pass through the virtual pivot point O and the axle member side attachment point 2c of the upper arm member 2 as shown in FIGS. than the ground point of the vertical line passing through the center of rotation of the auxiliary steering wheel W _L eggplant to ground at the rear of the vehicle.

Then, as viewed from the side of the vehicle as in Figure 4, the ground point of the king pin axis Kp, is the caster trail epsilon ₀ is less than the distance between the ground point of the vertical line passing through the center of rotation of the auxiliary steering wheel W _L The first lower link member 3 and the second lower link member 4 have the following special arrangement so as to achieve such a configuration.

  The lateral force applied point of the auxiliary steering wheel during vehicle travel moves from the ground contact point of the vertical line passing through the center of rotation of the auxiliary steering wheel to the rear of the vehicle, and the amount of movement depends on the vehicle traveling state such as the vehicle speed, tire pressure, etc. The pneumatic trail ε, which is the distance in the vehicle longitudinal direction from the ground contact point of the vertical line passing through the center of rotation of the auxiliary steering wheel to the lateral force application point of the auxiliary steering wheel, varies depending on the vehicle running conditions. It depends on the vehicle running conditions and vehicle running conditions such as tire pressure.

However, if the tire pressure is the design reference value and the vehicle running state is also within the normal range, that is, if it is a common sense and general running condition or running state, the pneumatic trail ε 5 has an occurrence probability density distribution as shown in FIG. 5, for example, and the occurrence probability is highest in a certain pneumatic trail εmax, and the occurrence probability tends to be lower as the pneumatic trail ε deviates from εmax.
This means that the most frequent traveling is such that the pneumatic trail ε has the maximum occurrence probability of the pneumatic trail εmax.

On the other hand, as shown in FIG. 6, the pneumatic trail ε becomes the arm length of the lateral force (cornering force) F acting on the side force applied point of the auxiliary steering wheel from the road surface, and the auxiliary steering wheels W _L and W _R are not rotated. Since the self-aligning torque M that returns to the rudder neutral position is generated, the relationship of the following equation is established among these three elements.
M = ε ・ F
The self-aligning torque M acts against the turning of the auxiliary steering wheels W _L and W _R , and increases the required driving force of the turning actuator 11 that controls the turning as described above.

Therefore, in order to achieve the object of the present invention to reduce the required driving force of the steering actuator 11, the self-aligning torque M needs to be zero, but the lateral force F cannot be reduced due to the steering characteristics. Therefore, in the end, there is no choice but to reduce the pneumatic trail ε.
Incidentally, since the caster rail ε ₀ described above with reference to FIG. 4 represents the dynamic tire contact point of the auxiliary steered wheel, if the caster rail ε ₀ is a suspension geometry that is the same as the pneumatic trail ε, self- The aligning torque M can be set to 0 to minimize the driving force required for the steering actuator 11 of the auxiliary steered wheel.

However, as described above, the pneumatic trail ε varies depending on the traveling state and traveling conditions and cannot be a fixed value.
Therefore, in this embodiment, the occurrence probability maximum pneumatic trail εmax that occurs most frequently in the case of common-sense and general driving conditions and driving conditions is used as the pneumatic trail ε,
Caster trail epsilon ₀ is to place the first lower link member 3 and second lower link member 4 to be the same as the probability maximum pneumatic trail .epsilon.max.

According to the auxiliary steering wheel suspension apparatus of the present embodiment having the above-described configuration, as clearly shown in FIG.
When viewed from the side of the vehicle, the virtual pivot point O provided by the first lower link member 3 and the second lower link member 4 is positioned so as to be located rearward of the axle member side attachment point 2c of the upper arm member 2. 1 lower link member and second lower link member are disposed, and
Similarly, when viewed from the side of the vehicle, a caster rail ε ₀ between the ground point of the kingpin axis Kp connecting the virtual pivot point O and the axle member side attachment point 2c of the upper arm member 2 and the auxiliary steering wheel rotation center is In order to arrange the first lower link member 3 and the second lower link member 4 to be the same as the occurrence probability maximum pneumatic trail εmax that occurs most frequently in the case of common-sense and general driving conditions and driving conditions,
Under the most frequently occurring driving conditions and driving conditions where the pneumatic trail ε of the secondary steered wheel has the maximum probability of occurrence of the pneumatic trail εmax, the kingpin axis Kp of the secondary steered wheel passes the lateral force point, The required driving force of the steering actuator 11 necessary for steering the steered wheels can be reduced.

Therefore, even with the limited output possible driving force of the steering actuator 11, the secondary steering wheel can be steered as required under all conditions where the steering of the secondary steering wheel is required.
The vehicle steering response improvement effect, the steering stability improvement effect, and the small turning performance improvement effect at low vehicle speeds can always be achieved as intended by turning the auxiliary steering wheel.

As shown in FIG. 4, when viewed from the side of the vehicle, the virtual pivot point O is located not only behind the axle member side attachment point 2c of the upper arm member 2, but also the center of rotation of the auxiliary steering wheel (rear wheel). It is better to place it directly below.
According to the arrangement of the virtual pivot point O, in addition to the above-described effect of reducing the required driving force of the actuator 11 at the time of turning of the auxiliary steering wheel, “Securing lateral force compliance steer amount” and “ The two performances of "improving rigidity" can be achieved at a high level.

Further, in the above arrangement of the first lower link member 3 and the second lower link member 4, as clearly shown in FIG. 2, the axle member side attachment point 3b and the second lower link of the first lower link member 3 are viewed from above the vehicle. The first lower link member 3 and the second lower link member 4 are preferably arranged so that the axle member side attachment point 4a of the link member 4 is as close as possible in design.
In this case, when the auxiliary steering wheel (rear wheel) is steered via the third lower link member 5 by the steering actuator 11, the axle member side attachment points 3b of the first lower link member 3 and the second lower link member 4 are provided. It is possible to minimize the twisting of the elastic bushing in 4b and to avoid an increase in the turning force of the auxiliary steered wheel (rear wheel) due to the twisting of the elastic bushing. it can.

In the above arrangement of the first lower link member 3 and the second lower link member 4, as clearly shown in FIG. 2, the first lower link member 3 is more than the second lower link member 4 than the axle member 1 as viewed from above the vehicle. The first lower link member 3 and the second lower link member 4 are preferably arranged so as to be largely inclined with respect to the auxiliary steering wheel support shaft portion.
In this case, the second lower link member 4 having a small inclination angle is more largely responsible for the lateral force than the first lower link member 3 having a large inclination angle. Securing can be assigned to the second lower link member 4, and
The first lower link member 3 having a larger inclination angle is more responsible for securing the lateral force compliance steer than the second lower link member 4 having the smaller inclination angle, and the securing of the lateral force compliance steer is the first. 1 can be assigned to the lower link member 3,
It is possible to achieve both the contact point lateral rigidity and the lateral force compliance steer that are in a trade-off relationship.

Here, as shown in FIGS. 3 and 4, the third lower link member 5 is arranged such that the axle member side attachment point 5b is located above the vehicle body side attachment point 5a.
According to the arrangement of the third lower link member 5, the roll steer characteristic during turning of the suspension device can be made appropriate.

Also, as shown in FIGS. 3 and 4, in arranging the first lower link member 3 and the second lower link member 4,
The first lower link member 3 and the second lower link member 4 are arranged so that the axle member side attachment point 4b of the second lower link member 4 is located above the axle member side attachment point 3b of the first lower link member 3. Deploy.
According to the arrangement of the first lower link member 3 and the second lower link member 4, the roll center height during turning and the rotation center locus of the auxiliary steering wheel can be made appropriate.

Further, when arranging the first lower link member 3 and the second lower link member 4, as shown in FIG. 2, the first lower link member 3 is more of the axle member 1 than the second lower link member 4 as viewed from above the vehicle. The first lower link member 3 and the second lower link member 4 are arranged so as to be largely inclined with respect to the auxiliary steering wheel support shaft portion.
According to the arrangement of the first lower link member 3 and the second lower link member 4, it is possible to increase the anti-lift angle that suppresses the rearward rise amount during braking of the vehicle, and to reduce the change in the vehicle body posture during braking. it can.

The upper arm member 2 is an A-type arm as shown in FIGS. 1 to 4, the bifurcated base ends 2a and 2b of the A-type arm are attached to the vehicle body side, and the axle member 1 is attached to the distal end 2c.
The use of such an A-type upper arm member 2 is advantageous in that the upper arm member 2 can be formed of a pressed part, which is advantageous in terms of cost and increases the longitudinal rigidity of the suspension device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall perspective view showing a vehicle auxiliary steering wheel suspension device according to an embodiment of the present invention as viewed from above a left auxiliary steering wheel. It is a top view which shows the suspension apparatus of the auxiliary steering wheel for vehicles which becomes the same Example seeing from the upper direction of a vehicle regarding a left auxiliary steering wheel. It is a front view which shows the suspension apparatus of the auxiliary steering wheel for vehicles which becomes the same Example seeing from the front of a vehicle regarding a left auxiliary steering wheel. It is a side view which shows the suspension apparatus of the auxiliary steering wheel for vehicles which becomes the same Example seeing from the left side of a vehicle. It is a distribution diagram which illustrates generation probability density distribution about a pneumatic trail of a sub steering wheel. It is explanatory drawing which shows the relationship between the pneumatic trail of a sub-steering wheel, lateral force, and self-aligning torque.

Explanation of symbols

W _L Left side steering wheel
W _R Right side steering wheel 1 Axle member 2 Upper arm member
2a, 2b Car body side attachment points
2c Axle member side attachment point 3 First lower link member
3a Car body side attachment point
3b Axle member side attachment point 4 Second lower link member
4a Car body side attachment point
4b Axle member side attachment point 5 Third lower link member for steering
5a Mounting point on the vehicle body
5b Axle member side attachment point 6 Upper arm member articulating rod 7 First lower link member articulating rod 8 Second lower link member articulating rod 9 Third lower link member articulating rod
10 Shock absorber
11 Steering actuator

Claims (6)

A vehicle in which an axle member having a shaft portion that rotatably supports the auxiliary steering wheel is suspended from the vehicle body in a manner that can be displaced in the vehicle vertical direction by a plurality of links extending inward in the vehicle width direction from the axle member. In the auxiliary steering wheel suspension device,
As the plurality of links,
An upper arm member extending between a position above the axle portion of the axle member and the vehicle body;
Three first lower link member extending between the lower portion and the vehicle body than the shaft portion of the axle member, and a second lower link member and the third lower link member is provided,
When viewed from the side of the vehicle, the first lower link member and the virtual pivot point provided by the first lower link member and the second lower link member are located rearward of the axle member side attachment point of the upper arm member and Arranging the second lower link member; and
Similarly, when viewed from the side of the vehicle, a caster rail between a grounding point of the kingpin axis connecting the virtual pivot point and the attachment point on the axle member side of the upper arm member and a grounding point of a vertical line passing through the center of the auxiliary steering wheel. The first lower link member and the second lower link member are arranged so as to be the same as the occurrence probability maximum pneumatic trail having the highest occurrence probability density with respect to the pneumatic trail of the auxiliary steering wheel ,
The third lower link member is constructed and arranged to control the steering of the auxiliary steering wheel by connecting a vehicle body side attachment point far from the axle member to the steering actuator. . In the vehicle auxiliary steering wheel suspension device according to claim 1,
When viewed from above the vehicle, placing the first lower link member of the axle-member-side attaching point and a second lower link member of the axle member side by the Hare first lower attachment point is proximity to each other link member and the second lower link member A suspension device for a vehicular auxiliary steering wheel, characterized by comprising: The suspension device for a secondary steering wheel for a vehicle according to claim 1 or 2,
The first lower link member and the second lower link member are arranged so that the first lower link member is inclined more largely with respect to the shaft portion of the axle member than the second lower link member when viewed from above the vehicle. A suspension device for the auxiliary steering wheel for a vehicle. The suspension device for a vehicle auxiliary steering wheel according to any one of claims 1 to 3,
The third lower link member is disposed such that an axle member side attachment point of the third lower link member is positioned above a connection point with respect to the steering actuator, which is a vehicle body side attachment point. Suspension device. The suspension device for a secondary steering wheel for a vehicle according to any one of claims 1 to 4,
The first lower link member and the second lower link member are arranged such that the axle member side attachment point of the second lower link member is located above the axle member side attachment point of the first lower link member. Suspension device for auxiliary steering wheel for vehicle. In the suspension device for the auxiliary steering wheel for a vehicle according to any one of claims 1 to 5 ,
A suspension device for a sub-steering wheel for a vehicle, wherein the upper arm member is an A-type arm, a bifurcated proximal end of the A-type arm is attached to the vehicle body side, and an axle member is attached to the tip.

Images