Construction vehicle

A control device that controls the degree of engagement of a modulation clutch connected to a power source on the basis of a travel drive force outputted from a travel device that comprises said modulation clutch, and that receives power from said power source via said modulation clutch and outputs said travel drive force, and a set drive force provided by a drive force setting device that sets said set drive force, comprising:

• a theoretical value determination means that determines a theoretical value, which is a value that said degree of engagement must assume in order to make the upper limit value of said travel drive force be equal to said set drive force;
• an operational state determination means that performs operational state determination by determining whether or not a work equipment for performing excavation and at least one other type of task is performing a task of a predetermined type and moreover said travel device is outputting said travel drive force in a predetermined travel direction;
• a drive force determination means that performs drive force determination by determining whether or not said travel drive force is greater than said set drive force;
• and
• a degree of engagement reduction means that, when the result of said operational state determination and the result of said drive force determination are both affirmative, reduces said degree of engagement so that said degree of engagement approaches towards said theoretical value, wherein
• when the result of said operational state determination and the result of said drive force determination are both affirmative, said degree of engagement reduction unit changes the rate at which said degree of engagement is decreased according to the magnitude of said theoretical value, so that said degree of engagement approaches towards said theoretical value, and
• when the result of said operational state determination and the result of said drive force determination are both affirmative, said degree of engagement reduction unit reduces the degree of engagement at a predetermined high speed rate when said theoretical value is greater than a predetermined reference value, while reducing the degree of engagement at a rate that is lower than said high speed rate when that is not the case.

A control method, implemented by a controller comprising a microprocessor and a memory, for controlling the degree of engagement of a modulation clutch connected to a power source on the basis of

• a travel drive force outputted from a travel device that comprises said modulation clutch, and that receives power from said power source via said modulation clutch and outputs said travel drive force, and
• a set drive force provided by a drive force setting device that sets said set drive force, wherein:
• an operational state determination is performed by the controller by determining whether or not a work equipment for performing excavation and at least one other type of task is performing a task of a predetermined type and moreover said travel device is outputting said travel drive force in a predetermined travel direction;
• a drive force determination is performed by the controller by determining whether or not said travel drive force is greater than said set drive force;
• when the result of said operational state determination and the result of said drive force determination are both affirmative, a theoretical value is determined by the controller, the theoretical value being a value that said degree of engagement must assume in order to make the upper limit value of said travel drive force be equal to said set drive force;
• said degree of engagement is reduced by the controller so that said degree of engagement approaches towards said theoretical value;
• when the result of said operational state determination and the result of said drive force determination are both affirmative, a rate at which said degree of engagement is decreased according to the magnitude of said theoretical value is changed by the controller so that said degree of engagement approaches towards said theoretical value;
• and
• when the result of said operational state determination and the result of said drive force determination are both affirmative, the degree of engagement at a predetermined high speed rate is reduced by the controller when said theoretical value is greater than a predetermined reference value, and the degree of engagement is reduced by the controller at a rate that is lower than said predetermined high speed rate when that is not the case.