The invention relates to a self-propelled construction machine, in particular a road milling machine, stabiliser, recycler or surface miner, which has a machine frame 2 supported by at least three running gears 10A, 10B, 11A, 11B, a drive device 14 for driving at least two running gears, and a work roller 4 arranged on the machine frame. The invention also relates to a method for controlling a construction machine of this kind. The drive device 14 comprises adjustable hydraulic motors 15, 16, 17, 18 associated with the drivable running gears, which hydraulic motors have a displacement volume Vg that can be varied by an adjusting device 15A, 16A, 17A, 18A, and comprises at least one adjustable travel drive-hydraulic pump 19 driven by at least one drive motor to supply the hydraulic motors with a variable total volume flow Q of hydraulic fluid. In addition, a controller 28 is provided which is configured in such a way that a partial volume flow Q.sub.1, Q.sub.2, Q.sub.3, Q.sub.4 is determined for each adjustable hydraulic motor 15, 16, 17, 18 from the total volume flow Q provided by the at least one travel drive-hydraulic pump 19, by means of which partial volume flow the particular hydraulic motor is to be operated, and when the speed n of an adjustable hydraulic motor increases as a result of slippage of the running gear associated with the adjustable hydraulic motor, the adjusting device of the adjustable hydraulic motor is controlled in such a way that a displacement volume Vg is set for the adjustable hydraulic motor, at which displacement volume the partial volume flow determined for the adjustable hydraulic motor is maintained. The self-propelled construction machine according to the invention is characterised in that a hydraulic flow divider is not required.

When an inclination angle is greater than or equal to a first threshold, a controller determines a displacement of a hydraulic pump from a command vehicle speed based on second pump data and determines a displacement of a hydraulic motor from the command vehicle speed based on second motor data. The second pump data defines the displacement of the hydraulic pump that is smaller than that of first pump data with respect to the command vehicle speed. The second motor data defines the displacement of the hydraulic motor that is smaller than that of first motor data with respect to the command vehicle speed.

In a working machine, a traveling pump is driven by a prime mover to rotate a traveling motor by fluid therefrom. The traveling motor has a rotation speed shiftable between a lower first speed and a higher second speed. A traveling change-over valve is shiftable between a first state where the rotation speed of the traveling motor is set to the first speed and a second state where the rotation speed of the traveling motor is set to the second speed. A controller performs a shock-mitigation for reducing a rotation speed of the prime mover when the traveling change-over valve is shifted from the second state to the first state. The controller determines a reduction amount of rotation speed of the prime mover reduced by the shock mitigation based on a difference between a target rotation speed of the prime mover and an actual rotation speed of the prime mover.

In a working machine, a traveling pump is driven by a prime mover to rotate a traveling motor by fluid therefrom. The traveling motor has a rotation speed shiftable between a lower first speed and a higher second speed. A traveling change-over valve is shiftable between a first state where the rotation speed of the traveling motor is set to the first speed and a second state where the rotation speed of the traveling motor is set to the second speed. A controller performs a shock-mitigation for reducing a rotation speed of the prime mover when the traveling change-over valve is shifted from the second state to the first state. The controller determines a reduction amount of rotation speed of the prime mover reduced by the shock mitigation based on a difference between a target rotation speed of the prime mover and an actual rotation speed of the prime mover.

An excavator includes a lower travelling body; an upper turning body mounted on the lower travelling body; a hydraulic pump installed in the upper turning body; a travelling hydraulic motor that is a variable displacement type motor configured to move the lower travelling body by being driven by hydraulic oil discharged by the hydraulic pump; and a control device configured to control a motor capacity of the travelling hydraulic motor so as to be switchable between a plurality of levels. The control device switches the motor capacity to a low rotation setting upon detecting that an operation for changing a travelling direction of the lower travelling body is performed.

A working machine includes a controller configured or programmed to perform an automatic deceleration for automatically decelerating a left traveling motor and a right traveling motor rotated at a second speed by shifting from the second speed to the first speed, and to determine a deceleration threshold that is used for judging whether the automatic deceleration has to be performed or not.

A working machine includes a prime mover, a traveling device, a traveling motor configured to output power to the traveling device, a speed shifting valve configured to shift an output speed of the traveling motor between a first speed and a second speed faster than the first speed, an actuation valve configured to change a hydraulic pressure applied to the speed shifting valve, a first fluid passage fluidly connected to the speed shifting valve so that hydraulic fluid having the hydraulic pressure to be applied to the speed shifting valve flows through the first fluid passage, a drain fluid passage fluidly connected to the first fluid passage, a brake shiftable between a braking state to brake the traveling motor and a braking releasing state to release the braking, and a controller configured or programmed to control the actuation valve and the brake, and being capable of activate a warm-up mode. The controller, when activating the warm-up mode, is configured or programmed to shift the brake into the braking state, and control the actuation valve so as to make the hydraulic pressure to be applied to the speed shifting valve equal to or greater than a value corresponding to the second speed.

A working machine includes a prime mover, a traveling pump configured to deliver hydraulic fluid at a flow rate corresponding to an angle of the swashplate, a traveling motor configured to be rotated by the hydraulic fluid delivered from the traveling pump so as to have a rotation speed shiftable between a first speed and a second speed higher than the first speed, a traveling change-over valve shiftable between a first state to set the rotation speed of the traveling motor to the first speed and a second state to set the rotation speed of the traveling motor to the second speed, an operation device, an operation valve configured to change the angle of the swashplate of the traveling pump according to operation of the operation device, an actuation valve provided upstream or downstream of the operation valve and fluidly connected to the operation valve, and a controller configured or programmed to output a control signal to control the actuation valve in such a way that, when the traveling change-over valve is shifted from the second state to the first state, a value of the control signal is reduced from a set value to a mitigation value less than the set value and then restores to the set value. The controller is configured or programmed to reduce the value of the control signal from the set value to the mitigation value for a mitigation period in such a way that a first reduction rate that is a rate of reducing the value of the control signal for a first part of the mitigation period between a start point thereof and an intermediate point thereof larger than a second reduction rate that is a rate of reducing the value of the control signal for a second part of the mitigation period between the intermediate point thereof and an end point thereof.

A working machine includes a prime mover, a traveling pump configured to deliver hydraulic fluid at a flow rate corresponding to an angle of the swashplate, a traveling motor configured to be rotated by the hydraulic fluid delivered from the traveling pump so as to have a rotation speed shiftable between a first speed and a second speed higher than the first speed, a traveling change-over valve shiftable between a first state to set the rotation speed of the traveling motor to the first speed and a second state to set the rotation speed of the traveling motor to the second speed, an operation device, an operation valve configured to change the angle of the swashplate of the traveling pump according to operation of the operation device, an actuation valve provided upstream or downstream of the operation valve and fluidly connected to the operation valve, and a controller configured or programmed to output a control signal to control the actuation valve in such a way that, when the traveling change-over valve is shifted from the second state to the first state, a value of the control signal is reduced from a set value to a mitigation value less than the set value and then restores to the set value. The controller is configured or programmed to reduce the value of the control signal from the set value to the mitigation value for a mitigation period in such a way that a first reduction rate that is a rate of reducing the value of the control signal for a first part of the mitigation period between a start point thereof and an intermediate point thereof larger than a second reduction rate that is a rate of reducing the value of the control signal for a second part of the mitigation period between the intermediate point thereof and an end point thereof.

In a working machine, a traveling pump is driven by a prime mover to rotate a traveling motor by fluid therefrom. The traveling motor has a rotation speed shiftable between a lower first speed and a higher second speed. A traveling change-over valve is shiftable between a first state where the rotation speed of the traveling motor is set to the first speed and a second state where the rotation speed of the traveling motor is set to the second speed. A controller performs a shock-mitigation for reducing a rotation speed of the prime mover when the traveling change-over valve is shifted from the second state to the first state. The controller determines a reduction amount of rotation speed of the prime mover reduced by the shock mitigation based on a difference between a target rotation speed of the prime mover and an actual rotation speed of the prime mover.