Construction machine having revolving structure

摘要

Both a hydraulic motor and an electric motor are provided for driving an upper swing structure. When the amount of electricity stored in a capacitor is appropriate, the upper swing structure is driven by both the hydraulic motor and the electric motor. When the amount of electricity stored in the capacitor exceeds an appropriate value, the mode is changed over to a mode in which the upper swing structure is driven only by the hydraulic motor, and an assist electric generation motor is assist-driven or engine-driven to thereby rapidly return the amount of electricity stored in the capacitor to an appropriate range. The capacity of the capacitor can be reduced, and the amount of electricity stored in the capacitor can be managed without losing the operability of swing motion.

主权项

1. A construction machine having a swing structure, comprising:
an engine; a hydraulic pump which is driven by the engine; the swing structure; a swing electric motor and a hydraulic motor which drive the swing structure; a swing operation lever which is operated by an operator to drive the swing structure; an assist electric motor which assist-drives the hydraulic pump during motoring and generates electric energy during drive using the engine; an electric storage device which stores electric energy to be supplied to the swing electric motor and the assist electric motor; and a controller which receives a signal corresponding to an operation amount and an operation direction on the swing operation lever and controls charge and discharge in the electric storage device, the controller configured to include a hydraulic and electric complex swing mode for driving the swing structure with total torque obtained by summing up torques of the swing electric motor and the hydraulic motor and a hydraulic alone mode for driving the swing structure with torque of only the hydraulic motor, and control charge and discharge in the electric storage device by changing over a mode between the hydraulic and electric complex swing mode and the hydraulic alone mode in a state where the hydraulic motor is driven, wherein,
the controller stores, for an amount of electricity stored in the electric storage device, an upper limit value and a lower limit value of a normal use region which is an optimal use range of the electric storage device, a regeneration prohibition value which is set to be larger than the upper limit value of the normal use region and to be smaller than a maximum amount of electricity stored in the electric storage device, and a swing prohibition value which is set to be smaller than the lower limit value of the normal use region and to be larger than a minimum amount of electricity stored in the electric storage device; andwhen the amount of electricity stored in the electric storage device is in between the upper limit value and the lower limit value of the normal use range, the controller drives and brakes the swing structure in the hydraulic and electric complex swing mode;when the amount of electricity stored in the electric storage device exceeds the upper limit value of the normal use range and reaches the regeneration prohibition value, the controller drives and brakes the swing structure in the hydraulic alone mode while motoring the assist electric motor so as to consume the electric energy stored in the electric storage device;conversely when the amount of electricity stored in the electric storage device falls below the lower limit value of the normal use range and reaches the swing prohibition value, the controller drives and brakes the swing structure in the hydraulic alone mode while using the engine to drive the assist electric motor so as to charge the electric storage device;while the amount of electricity stored in the electric storage device reaches from the upper limit value to the regeneration prohibition value, the controller motors the assist electric motor at a maximum output; andwhile the amount of electricity stored in the electric storage device reaches from the lower limit value to the swing prohibition value, the controller controls the assist electric motor to perform motor generating operation at a maximum output.