Work vehicle

1. A work vehicle, comprising:

a work implement including a boom, an arm, and a bucket;

a weight specifying portion which specifies a weight of said bucket attached to said arm;

a distance obtaining portion which obtains a distance between a cutting edge of said bucket and target design topography; and

a stop control unit which carries out stop control for stopping an operation of said work implement before said cutting edge of said bucket reaches said target design topography when said cutting edge of said bucket comes closer to said target design topography, and carries out control, when a moving speed of said bucket in a direction toward said target design topography is equal in both of a first specifying state in which said weight specifying portion specifies a weight of said bucket as a first weight and a second specifying state in which said weight specifying portion specifies a weight of said bucket as a second weight smaller than said first weight, such that the moving speed of said bucket in the direction toward said target design topography is reduced from a position more distant from said target design topography in said first specifying state than in said second specifying state.

2. The work vehicle according to claim 1 , wherein

said stop control unit has

a storage portion storing a plurality of pieces of relation data corresponding to a plurality of weights of said buckets, respectively, each of the plurality of pieces of relation data defining relation between a distance between said cutting edge of said bucket and said target design topography and a speed limit of said cutting edge of said bucket,

a selection portion selecting one piece of relation data among the plurality of pieces of said relation data stored in said storage portion, based on the weight of said bucket specified by said weight specifying portion, and

a speed limit obtaining portion obtaining said speed limit of said cutting edge of said bucket based on said distance obtained by said distance obtaining portion, by using said one piece of relation data selected by said selection portion, and

said stop control unit carries out said stop control based on said speed limit of said cutting edge of said bucket.

3. The work vehicle according to claim 2 , wherein

the plurality of pieces of said relation data include first relation data and second relation data,

the weight of said bucket when said first relation data is selected is larger than the weight of said bucket when said second relation data is selected, and

said distance in said first relation data at which reduction in said speed limit of said cutting edge of said bucket is started is larger than said distance in said second relation data at which reduction in said speed limit of said cutting edge of said bucket is started.

4. The work vehicle according to claim 3 , wherein

said first relation data has a first deceleration section and a second deceleration section, and

said first deceleration section is set at a position closer to said target design topography than said second deceleration section and a degree of deceleration with change in distance between said cutting edge of said bucket and said target design topography in said second deceleration section is larger than a degree of deceleration with change in distance between said cutting edge of said bucket and said target design topography in said first deceleration section.

5. The work vehicle according to claim 4 , wherein

said second relation data has a third deceleration section and a fourth deceleration section,

said third deceleration section is set at a position closer to said target design topography than said fourth deceleration section and a degree of deceleration with change in distance between said cutting edge of said bucket and said target design topography in said fourth deceleration section is larger than a degree of deceleration with change in distance between said cutting edge of said bucket and said target design topography in said third deceleration section, and

said fourth deceleration section is set at a position closer to said target design topography than said second deceleration section.

6. The work vehicle according to claim 2 , further comprising:

an estimated speed determination portion which estimates a speed of said boom based on an amount of operation of an operation member; and

a direction control valve which has a movable spool and controls supply of a hydraulic oil to a hydraulic cylinder driving said work implement as said spool moves, wherein

said storage portion stores a plurality of pieces of correlation data corresponding to a plurality of weights of said buckets, respectively, each pieces of correlation data showing relation between a cylinder speed of said hydraulic cylinder and an operation command value for operating said hydraulic cylinder,

said estimated speed determination portion selects one piece of correlation data from among the plurality of pieces of said correlation data stored in said storage portion based on the weight of said bucket specified by said weight specifying portion and obtains an estimated speed of said boom by using selected said one piece of correlation data, and

said stop control unit carries out said stop control based on said estimated speed of said boom and said speed limit of said boom.

7. The work vehicle according to claim 1 , further comprising a hydraulic cylinder which drives said work implement, wherein

said weight specifying portion specifies a weight of said bucket attached to said arm based on a pressure generated in said hydraulic cylinder while said bucket is in air.

8. The work vehicle according to claim 1 , further comprising a monitor onto which an operator can perform an operation for input of a weight of said bucket, wherein

said weight specifying portion specifies a weight of said bucket attached to said arm based on the weight of said bucket input to said monitor by said operator.