CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. JP2020-044413 filed on Mar. 13, 2020, the content of which is hereby incorporated by reference in its entirety into this application.

BACKGROUND

1. Technical Field

The present disclosure relates to a three-row wheel vehicle that has a front wheel group, a center wheel group and a rear wheel group and in which at least one of the front wheel group, center wheel group and rear wheel group includes a pair of wheels spaced laterally.

2. Description of the Related Art

As a self-propelled vehicle, various special vehicles with excellent traversability on rough terrain, steps, etc. are known. In order for a vehicle to travel on rough terrain, it is necessary for the wheels to have better performance over an protrusion or the like than a general vehicle such as an automobile. A vehicle such as a self-propelled trolley that transports luggage also needs to have excellent performance of wheels riding on a step, as in a case of riding on a sidewalk from a general road.

As a means for easily passing over a protrusion and climbing on a step, it is conceivable to raise a front wheel group when the front wheel group approaches a protrusion and a step. For example, in Japanese Patent Application Laid-open Publication No. 2012-228996, a vehicle having a front wheel, center wheels, and a rear wheel is described, which is configured so that the front wheel can easily be raised to pass over a protrusion or climb on a step by adjusting lengths of the links connecting the front wheel and the center wheels and an offset angle in the lateral direction of the links.

In the vehicle described in Japanese Patent Application Laid-open Publication No. 2012-228996, when the front wheel approaches a step or the like, the front wheel can be easily lifted, but since the front wheel is not actively raised, the front wheel cannot get over a step when a height of the step is high. Further, by adjusting the lengths of the links connecting the front wheel and the center wheels and the offset angle in the lateral direction of the links, a position of a center of gravity of the vehicle is inevitably changed, so that running stability of the vehicle tends to deteriorate.

SUMMARY

The present disclosure provides a three-row wheel vehicle which is improved so as to easily ride on a step or the like by effectively utilizing not only an upward force but also a rearward force received by a front wheel group from a step or the like to move the front wheel group upward.

According to the present disclosure, a three-row wheel vehicle is provided which has a front wheel group, a center wheel group and a rear wheel group that are arranged in a front-rear direction of the three-row wheel vehicle, and at least one of the front wheel group, the center wheel group and the rear wheel group includes a pair of laterally spaced wheel.

The three-row wheel vehicle has a pair of laterally spaced leading arms, a pair of laterally spaced swing arms and a pair of laterally spaced connecting links.

Each leading arm is connected at a rear end portion to a vehicle body so as to pivot in a vertical direction around a first lateral pivot axis; each swing arm is connected to a front end portion of the leading arm so as to swing in the front-rear direction around a second lateral pivot axis and rotatably supports the corresponding wheel of the front wheel group at a lower end portion; and each connecting link is attached at one end to the swing arm so as to pivot around a third lateral pivot axis and is attached at the other end to the vehicle body so as to pivot around a fourth lateral pivot axis.

Heights of the third and fourth lateral pivot axes are different from each other when the three-row wheel vehicle is on a horizontal flat traveling road, and each connecting link is arranged to apply a reaction force including an upward component to the swing arm when a rearward force acts from the corresponding wheel of the front wheel group to the one end via the swing arm.

According to the above configuration, the vehicle has a pair of laterally spaced leading arms, a pair of laterally spaced swing arms and a pair of laterally spaced connecting links. Each leading arm is connected at the rear end to the vehicle body so as to pivot in the vertical direction around the first lateral pivot axis. Each swing arm is connected to the front end portion of the leading arm so as to swing in the front-rear direction around the second lateral pivot axis and rotatably supports the corresponding wheel of the front wheel group at the lower end portion. Each connecting link is attached at one end to the swing arm so as to pivot around the third lateral pivot axis and is attached at the other end to the vehicle body so as to pivot around the fourth lateral pivot axis.

When the front wheel group reaches a step, each front wheel receives not only an upward force but also a rearward force from the step. The upward force is transmitted to the leading arm by the swing arm, so that the leading arm is pivoted upward around the rear end portion. Furthermore, the heights of the third and fourth pivot axes are different from each other when the three-row wheel vehicle is on a horizontal flat traveling road. When a rearward force acts from the front wheel to the one end of the connecting link via the swing arm, a reaction force including an upward component is applied to the swing arm by the connecting link and transmitted to the leading arm. Therefore, this also causes the leading arm to be pivoted upwards around the rear end portion.

Accordingly, as compared to where the connecting link arranged as described above is not provided, the leading arm can be efficiently pivoted upward around the rear end portion, so that the front wheel can be actively moved upward through the swing arm. Therefore, since the front wheel can be moved upward by effectively utilizing not only the upward force received by the front wheel from a step or the like but also a reaction force of the rearward force, the front wheel can easily ride on the step or the like.

In particular, as will be described in detail later, when a height of a step or the like is equal to or larger than a radius of the front wheel, the upward force becomes 0 and only the rearward force is applied. Even in such a situation, the front wheel can be moved upward by the above-mentioned action of the link mechanism. Therefore, even if the height of the step or the like is equal to or larger than the radius of the front wheel, the front wheel can ride on the step or the like as long as the height is not excessive.

Even if the leading arm and the like are pivoted when the front wheel ride on a step or the like, a center of gravity of the vehicle does not substantially change in the front-rear direction or the lateral direction, so that running stability of the vehicle does not deteriorate.

In one aspect of the present disclosure, the third lateral pivot axis is located below the second lateral pivot axis, and the fourth lateral pivot axis is located behind and below the third lateral pivot axis when the three-row wheel vehicle is on the horizontal flat traveling road.

According to the above configuration, when a rearward force acts on the one end of the connecting link from the front wheel via the swing arm, the connecting link receives a compressive load, and as a result, a reaction force in the direction from the other end to the one end is generated. The third axis is located below the second axis, and the fourth axis is behind and below the third axis when the three-row wheel vehicle is on a horizontal flat traveling road. Therefore, since the reaction force includes an upward component, an upward force can be applied to the swing arm.

In one aspect of the present disclosure, the third lateral pivot axis is located below the second lateral pivot axis, and the fourth lateral pivot axis is located anterior to and above the third lateral pivot axis when the three-row wheel vehicle is on the horizontal flat traveling road.

According to the above configuration, when a rearward force acts on the one end of the connecting link from the front wheel via the swing arm, the connecting link receives a tensile load, and as a result, a reaction force in the direction from the other end to the one end is generated. The third axis is located below the second axis, and the fourth axis is anterior to and above the third axis when the three-row wheel vehicle is on a horizontal flat traveling road. Therefore, since the reaction force includes an upward component, an upward force can be applied to the swing arm.

In one aspect of the present disclosure, each leading arm supports the corresponding wheel of the center wheel group rotatably around a rotation axis at a position below the first lateral pivot axis.

According to the above aspect, there is no need for a dedicated link to rotatably support the corresponding wheel of the center wheel group. In addition, since the leading arm rotatably supports the center wheel below the first pivot axis, when the center wheel is in a situation of riding on a step and a rear force acts on the center wheel, the leading arm receives a moment in the direction of lowering the front end portion around the first pivot axis. Therefore, the leading arm tries to push down the swing arm and the front wheel downward, but if the front wheel has already climbed on the step, it does not descend, so that the center wheel is lifted by a reaction force of the moment. Therefore, the center wheel can be easily driven onto a step.

Further, in another aspect of the present disclosure, the rotation axis of the corresponding wheel of the center wheel group is located directly below the first lateral pivot axis when the three-row wheel vehicle is on the horizontal flat traveling road.

According to the above aspect, when the leading arm pivots around the first lateral pivot axis, the rotation axis of the center wheel moves around the first lateral pivot axis, so that a height of the center wheel rises slightly and does not descend. Therefore, even if a load of the three-row wheel vehicle is high and a ground contact load of each wheel is high, it is possible to avoid hindering the pivotal movement of the leading arm due to an increase in the force with which the center wheel pushes the traveling road downward.

In the present application, all terms indicating the positional relationship and direction between members such as “front”, “rear”, “front and back”, “forward”, “rearward”, and “lateral” mean front, rear, front-back, forward, rearward, and lateral directions about the vehicle unless otherwise specified. Further, in the present application, a pair of front wheels, a pair of center wheels and a pair of rear wheels are collectively referred to as a front wheel group, a center wheel group and a rear wheel group, respectively, as necessary.

Other objects, other features and attendant advantages of the present disclosure will be readily understood from the description of the embodiments of the present disclosure described with reference to the following drawings.

