The invention relates to the technical field of
engineering machinery, and discloses a variable-amplitude hydraulic
system,
engineering machinery and a variable-
amplitude control method. The variable-amplitude hydraulic
system comprises a variable-amplitude oil cylinder, a
pressure detection module, an oil way module, a first
pilot oil way module and a control module. The
pressure detection module is used for detecting the
oil pressure of the rod cavity; the oil way module comprises a first oil way module and a first balance valve, the first oil way module is connected with a rod cavity of the variable-amplitude oil cylinder, and the first balance valve is arranged on a first oil way; the first
pilot oil way module is connected with the control end of the first balance valve. The control module is configured to send out a
stop signal used for controlling stopping of current work under the condition that the
oil pressure detected by the
pressure detection module is larger than a preset safety value, and / or control the
pilot oil way module to open an oil return working position of the first balance valve for oil return. According to the variable-amplitude hydraulic
system, when the pressure of a variable-amplitude oil cylinder rod cavity is larger than a preset safety value, oil return is actively started,
equipment safety is protected, and the service life is prolonged.