Construction machine

1 . A construction machine, comprising:

a machine body;

a work device including a boom supported to the machine body to be capable of being raised and lowered, an arm rotatably supported to the boom, and a bucket supported to the arm, the bucket having a bucket base end portion that is a base end portion rotatably attached to the arm about a horizontal axis, a bucket tip portion that is a tip portion on an opposite side of the bucket base end portion, and an inner surface defining an accommodation space that is a space capable of accommodating earth and sand;

at least one operation device including an operation lever configured to be operated by an operator, the at least one operation device being configured to cause the work device to perform excavation work so that earth and sand on a ground is excavated by displacing the bucket with respect to the ground while maintaining a state where a portion including at least the bucket tip portion is in contact with the ground at an excavation attitude that is a bucket attitude at which the bucket base end portion is disposed at a position higher than the bucket tip portion and is an attitude at which the earth and sand on the ground is capable of being excavated; and

a controller,

wherein the controller

determines, during the excavation work, a contact state between a specific upper region and the earth and sand, the specific upper region being a portion located at an upper portion on the inner surface of the bucket at the excavation attitude, and

outputs, in a case where the controller determines that the earth and sand is in contact with the specific upper region on the inner surface of the bucket during the excavation work, a resistance reduction command signal that is a command signal for operating the work device so that the bucket is displaced in a resistance reduction direction that is a direction where excavation resistance acting on the bucket is capable of being reduced, the resistance reduction direction being a direction in which a position of the horizontal axis which is a rotation center of the bucket base end portion is displaced upward or obliquely upward.

2 . The construction machine according to claim 1 , wherein

the controller

outputs the resistance reduction command signal in a case where a determination is made that the earth and sand is in contact with the specific upper region of the bucket, and

does not output the resistance reduction command signal in a case where a determination is made that the earth and sand is not in contact with the specific upper region of the bucket.

3 . The construction machine according to claim 1 , wherein

the controller

outputs the resistance reduction command signal in a case where a determination is made that the earth and sand is not in contact with the specific upper region of the bucket and an amount of the earth and sand accommodated in the accommodation space of the bucket is greater than an earth and sand amount threshold that is a predetermined threshold, and

does not output the resistance reduction command signal in a case where a determination is made that the earth and sand is not in contact with the specific upper region of the bucket and the amount of the earth and sand accommodated in the accommodation space of the bucket is equal to or lower than the earth and sand amount threshold.

4 . The construction machine according to claim 1 , wherein

the controller

outputs the resistance reduction command signal in a case where a determination is made that the earth and sand is not in contact with the specific upper region of the bucket and an excavation reaction force that is a reaction force received by the bucket from the ground in the excavation work is greater than a reaction force threshold that is a predetermined threshold, and

does not output the resistance reduction command signal in a case where a determination is made that the earth and sand is not in contact with the specific upper region of the bucket and the excavation reaction force is equal to or lower than the reaction force threshold.

5 . The construction machine according to claim 1 , further comprising:

a work device attitude information acquisition device that acquires work device attitude information that is information regarding an attitude of the work device; and

an earth and sand information acquisition device that acquires earth and sand information that is information regarding the earth and sand accommodated in the accommodation space of the bucket,

wherein the controller calculates a bucket attitude that is the attitude of the bucket using the work device attitude information, and calculates an accumulation state of the earth and sand in the accommodation space of the bucket using the bucket attitude and the earth and sand information, and

the controller determines the contact state between the specific upper region and the earth and sand based on the accumulation state.

6 . The construction machine according to claim 1 , further comprising a load detector that is disposed in the specific upper region and is configured to detect an earth and sand load that is a load received from the earth and sand accommodated in the accommodation space of the bucket,

wherein the controller determines the contact state between the specific upper region and the earth and sand based on the earth and sand load detected by the load detector.

7 . The construction machine according to claim 1 , wherein

the controller calculates a tilt index value that is an index value corresponding to a tilt of the specific upper region with respect to a predetermined reference plane, and

the controller does not output the resistance reduction command signal in a case where the tilt index value is greater than a tilt threshold that is a predetermined threshold.