1. A work vehicle automatic traveling system for a plurality of work vehicles that carry out work travel cooperatively in a work site while exchanging data, the system comprising: an area setting unit that sets the work site to an outer peripheral area, and an area to be worked on an inner side of the outer peripheral area; a host vehicle position calculating unit that calculates a host vehicle position; a route managing unit that manages a travel route element set and a circling route element set so as to be capable of readout, the travel route element set being an aggregate of multiple travel route elements constituting a travel route that covers the area to be worked, and the circling route element set being an aggregate of circling route elements constituting a circling route that goes around the outer peripheral area; a route element selecting unit that, on the basis of state information, sequentially selects a next travel route element, on which the work vehicle is to travel next, from the travel route element set, or a next circling route element, on which the work vehicle is to travel next, from the circling route element set; and an autonomous travel controlling unit that executes autonomous travel on the basis of the next travel route element and the host vehicle position, wherein the route element selecting unit includes a cooperative route element selection rule employed when the plurality of work vehicles carry out work travel cooperatively in the area to be worked, and an independent route element selection rule employed when one of the work vehicles acts as an independent work vehicle and carries out independent work travel in the area to be worked; and when the independent work vehicle is carrying out independent work travel in the area to be worked, and a work vehicle aside from the host vehicle is carrying out circling travel based on the circling route element or is stopped, the route element selecting unit of the independent work vehicle selects the next travel route element on the basis of the independent route element selection rule.

2. The work vehicle automatic traveling system according to claim 1, wherein the travel route element set is a mesh line set constituted by mesh lines that divide the area to be worked into a mesh; points where the mesh lines intersect are set as route changeable points where the route of the work vehicle is permitted to be changed; under the cooperative route element selection rule, the next travel route element is selected so that a compound spiral-shaped travel trajectory created by a plurality of spiral-shaped travel trajectories made by the work vehicle covers the area to be worked; and under the independent route element selection rule, the next travel route element is selected so that the spiral-shaped travel trajectory made by the independent work vehicle covers the area to be worked.

3. The work vehicle automatic traveling system according to claim 1, wherein the travel route element set is a parallel line set constituted by mutually-parallel lines that divide the area to be worked into rectangular shapes; movement from one end of one travel route element to one end of another travel route element is executed through U-turn travel by the work vehicle; under the cooperative route element selection rule, the travel route element where a work vehicle aside from the host vehicle is located, and a travel route element adjacent to the stated travel route element, are excluded from being selected as the next travel route element; and under the independent route element selection rule, the travel route element moving toward the work vehicle aside from the host vehicle, located in the outer peripheral area, is excluded from being selected as the next travel route element.

4. A work vehicle automatic traveling system for a plurality of work vehicles that carry out work travel cooperatively in a work site while exchanging data, the system comprising: a host vehicle position calculating unit that calculates a host vehicle position; a route managing unit that calculates a travel route element set, the travel route element set being an aggregate of multiple travel route elements constituting a travel route covering the area to be worked, and stores the travel route element set so as to be capable of readout; and a route element selecting unit that selects a next travel route element, which is to be traveled next, sequentially from the travel route element set, on the basis of the host vehicle position and a work travel state of another vehicle.

5. The work vehicle automatic traveling system according to claim 4, wherein an other vehicle positional relationship indicating a positional relationship between the host vehicle and another vehicle is included in the work travel state of the other vehicle; and the system further comprises an other vehicle positional relationship calculating unit that calculates the other vehicle positional relationship.

6. The work vehicle automatic traveling system according to claim 5, wherein the other vehicle positional relationship calculating unit calculates an estimated contact position between the work vehicles on the basis of the other vehicle positional relationship; and when the estimated contact position has been calculated, the work vehicle that will pass the estimated contact position at a later time is temporarily stopped.

7. The work vehicle automatic traveling system according to claim 6, wherein the other vehicle positional relationship calculating unit calculates the estimated contact position on the basis of the other vehicle positional relationship, and the travel route elements where the plurality of work vehicles are traveling.

WE CLAIM:
1. A work vehicle automatic traveling system for a plurality of work
vehicles that carry out work travel cooperatively in a work site while exchanging data, the system comprising:
an area setting unit that sets the work site to an outer peripheral area, and an area to be worked on an inner side of the outer peripheral area;
a host vehicle position calculating unit that calculates a host vehicle position;
a route managing unit that manages a travel route element set and a circling route element set so as to be capable of readout, the travel route element set being an aggregate of multiple travel route elements constituting a travel route that covers the area to be worked, and the circling route element set being an aggregate of circling route elements constituting a circling route that goes around the outer peripheral area;
a route element selecting unit that, on the basis of state information, sequentially selects a next travel route element, on which the work vehicle is to travel next, from the travel route element set, or a next circling route element, on which the work vehicle is to travel next, from the circling route element set; and
an autonomous travel controlling unit that executes autonomous travel on the basis of the next travel route element and the host vehicle position,
wherein the route element selecting unit includes a cooperative route element selection rule employed when the plurality of work vehicles carry out work travel cooperatively in the area to be worked, and an independent route element selection rule employed when one of the work vehicles acts as an independent work vehicle and carries out independent work travel in the area to be worked; and
when the independent work vehicle is carrying out independent work travel in the area to be worked, and a work vehicle aside from the host vehicle is carrying out circling travel based on the circling route element or is stopped, the route element selecting unit of the independent work vehicle selects the next travel route element on the basis of the independent route element selection rule.

2. The work vehicle automatic traveling system according to claim 1,
wherein the travel route element set is a mesh line set constituted by
mesh lines that divide the area to be worked into a mesh;
points where the mesh lines intersect are set as route changeable points where the route of the work vehicle is permitted to be changed;
under the cooperative route element selection rule, the next travel route element is selected so that a compound spiral-shaped travel trajectory created by a plurality of spiral-shaped travel trajectories made by the work vehicle covers the area to be worked; and
under the independent route element selection rule, the next travel route element is selected so that the spiral-shaped travel trajectory made by the independent work vehicle covers the area to be worked.
3. The work vehicle automatic traveling system according to claim 1,
wherein the travel route element set is a parallel line set constituted
by mutually-parallel lines that divide the area to be worked into rectangular shapes;
movement from one end of one travel route element to one end of another travel route element is executed through U-turn travel by the work vehicle;
under the cooperative route element selection rule, the travel route element where a work vehicle aside from the host vehicle is located, and a travel route element adjacent to the stated travel route element, are excluded from being selected as the next travel route element; and
under the independent route element selection rule, the travel route element moving toward the work vehicle aside from the host vehicle, located in the outer peripheral area, is excluded from being selected as the next travel route element.
4. A work vehicle automatic traveling system for a plurality of work
vehicles that carry out work travel cooperatively in a work site while
exchanging data, the system comprising:
a host vehicle position calculating unit that calculates a host vehicle position;
a route managing unit that calculates a travel route element set, the travel route element set being an aggregate of multiple travel route elements

constituting a travel route covering the area to be worked, and stores the travel route element set so as to be capable of readout; and
a route element selecting unit that selects a next travel route element, which is to be traveled next, sequentially from the travel route element set, on the basis of the host vehicle position and a work travel state of another vehicle.
5. The work vehicle automatic traveling system according to claim 4,
wherein an other vehicle positional relationship indicating a
positional relationship between the host vehicle and another vehicle is included in the work travel state of the other vehicle; and
the system further comprises an other vehicle positional relationship calculating unit that calculates the other vehicle positional relationship.
6. The work vehicle automatic traveling system according to claim 5,
wherein the other vehicle positional relationship calculating unit
calculates an estimated contact position between the work vehicles on the basis of the other vehicle positional relationship; and
when the estimated contact position has been calculated, the work vehicle that will pass the estimated contact position at a later time is temporarily stopped.
7. The work vehicle automatic traveling system according to claim 6,
wherein the other vehicle positional relationship calculating unit
calculates the estimated contact position on the basis of the other vehicle positional relationship, and the travel route elements where the plurality of work vehicles are traveling.