Method and apparatus for automatically controlling the motoromloebstallet of a ground construction apparatus

摘要

1. A device for automatically controlling the engine speed of an earthmoving machine having an internal combustion engine, more particularly a hydraulic excavator having a diesel engine, between a working speed and a second speed below said working speed, comprising a hydraulic circuit (6) fed by at least one hydraulic pump (3, 4) to actuate a working tool, a pick-up (9) which is disposed in the hydraulic circuit (6) and which is (pressure-)controlled by the pressure in the hydraulic circuit (6), and a control element (21), by means of which there is actuated, on the one hand, a control lever (26) disposed in the area of the driver's seat and adjustable manually there and, on the other hand, a speed adjusting lever (33) acting on the internal combustion engine fuel regulator, the control element (21) being adapted to be so actuated, via a control line (38), by means of a switch (17, 18) connected to the pick-up (9) via a delay means (12), the actuation being provided by controlled application of a separate energy source (19), that the connection between the energy source (19) and the control element (21) is blocked when a predetermined critical pressure is exceeded in the hydraulic circuit (6) so that the control element (21) returns the speed adjusting lever (33) to the working speed set at the control lever (26), and the connection between the energy source (19) and the control element (21) can be released with a controlled delay by the delay means (12) when the predetermined critical pressure in the hydraulic circuit (6) is not attained, so that the control element (31) adjusts the speed adjusting lever (33) without adjusting the control lever (26) to the idling position.