Caterpillar Sarl

Koichi Kiyasu

Hideki Nakajima

Shuhei Orimoto

Toshikazu Koga

Hiroshi Maeda

Problem: Provide a hydraulic circuit of a construction machinery that can effectively use the excess flow rate of the first hydraulic pump. Solution: In the hydraulic circuit, when signals are output from the first travel operator, the second travel operator, and the actuator operator, hydraulic oil is supplied from the first hydraulic pump to the actuator switch valve. Hydraulic oil is also supplied from the second hydraulic pump to the first travel switch valve and the second travel switch valve. Further, according to the signal output from the actuator operator, the opening degree of the communication valve is adjusted to control the supply amount of hydraulic oil sent from the first pump line to the second pump line.

Hydraulic circuit of a construction machinery

PROBLEM: To avoid the pressure of the actuator oil passage from becoming higher or equal to the upper limit pressure that is set depending on an individual option hydraulic actuator, during non-operation of an option operation lever, even if the actuator oil passage connected to the option hydraulic actuator is not provided with a variable relief valve. SOLUTION: It is configured to release the pressure of the actuator oil passage into the oil tank via the option control valve, the load pressure introducing oil passage, the variable relief valve, by switching the option control valve to load pressure relief positions at which the pressure of the actuator oil passage is allowed to flow into the load pressure introducing oil passage, when the pressure of the actuator oil passages exceeds the upper limit pressure during non-operation of the option operation lever; as well as by controlling the relief setting pressure of the variable relief valve connected to the load pressure introducing oil passage so as to be less than or equal to the upper limit pressure.

Hydraulic control system in working machine

To put new thought to a control method, and to obtain good operability, upon providing a control circuit for option hydraulic actuator in a hydraulic circuit for a working machine. There is provided an option merging oil passage that allows the discharge oil of the first, second hydraulic pumps to be merged thereinto, and the option merging oil passage is provided with an option control valve and a compensator valve, and is configured such that a variable relief valve is connected to a signal pressure introduction oil passage connected to the compensator valve, a supply pressure to an option hydraulic actuator can be variably controlled by changing a relief setting pressure of the variable relief valve; on the other hand, distributed flow rate computation with respect to the other hydraulic actuators, opening area control of the option control valve, the other hydraulic actuators control valves, and discharge pressure control of the first, second hydraulic pumps are optimized.

In optional control circuit commonly used among multiple optional hydraulic actuators, it is necessary to enable back pressure reduction, part reduction, and downsizing when a breaker is mounted as an optional hydraulic actuator. A normal control region, where the discharge valve passage to the oil tank has an opening area of normal control range, and a back pressure reduction region, where the discharge valve passage has the back pressure reduction opening Aw whose opening area is larger than the maximum opening area in the normal control range, are installed at the operating position of optional control valve for controlling discharge flow rate of optional hydraulic actuator; when the optional hydraulic actuator is the breaker, the optional control valve is positioned at the back pressure reduction region (W), when the optional hydraulic actuator is not the breaker, the valve is positioned at the normal control region.

Hydraulic control system in working machines

Problem: Calibrating a correspondence relationship between a pump control current value and a pump flow rate of the hydraulic pump in a hydraulic system including a variable capacity hydraulic pump whose capacity is variably controlled according to the pump control current value, a flow rate control valve whose opening area is variably controlled according to a valve control current value, and a pressure compensation valve that maintains differential pressure before and after the flow control valve to be constant is made in a precise and simple manner. Solution: The spool valve has a configuration in which the pump control current value is sweepingly increased and the peak of a change of pump pressure during the sweeping increase is calibrated as the pump control current value of the pump flow rate of the target flow rate, with the spool valve held in the aperture area corresponding to the spool valve output flow rate of the arbitrary target flow rate. With the spool valve maintained at an opening area corresponding to an output flow rate of the spool valve of an arbitrary target flow rate, the pump control current value sweepingly increases, and the peak of the change of the pump pressure during the sweeping increase is calibrated as the pump control current value of the pump flow rate of the target flow rate.

Calibration system and calibration method in hydraulic system

To avoid a large size of a direction change-over valve and enable accurate supply flow control when providing a flow control valve at an upstream side of the direction change-over valve to change the relationship between supply flow rate and discharge flow rate for a hydraulic actuator. The configuration is to control a supply flow rate to a stick cylinder based on an opening area of the stick's direction change-over valve and stick's flow control valve, calculate a target opening area of the stick's flow control valve based on a target supply flow rate from hydraulic pumps A, B to the stick cylinder, the opening area of the stick's direction change-over valve, and a target differential pressure between hydraulic pump A and a load pressure of stick cylinder, and control the stick's flow control valve so as to keep the target opening area calculated.

Hydraulic control system

To achieve improvement in work efficiency of calibration work and improvement in calibration accuracy, by performing control so that the time taken to increase the sweep of an applied current becomes substantially constant, upon the calibration of a valve opening position current value when a valve operated by electrical current applied to an electrical actuator opens a flow passage. There is provided a predicted value calculating means for predicting a calibration value of a valve opening position current value on the basis of information concerning valve opening position current values, and the sweep starting current value is set so that the time taken to increase the sweep to a predicted value predicted by the predicted value calculating means from a sweep start becomes a fixed time.

Valve calibration system and calibration method

To perform a work with the same operability under a dead weight of a front work equipment in any of a float work and a normal work, when a bucket descends in the air, and after contacting the ground, to perform a work with the operability being maintained as it is when performing the float work, and to perform a work while pressurized hydraulic fluid is supplied from a hydraulic pump when performing the normal work. A lower-ing control during a float working mode is performed in a valve passage state in a first region at which the lowering control is performed under the dead weight of the from work equip-ment without being supplied with hydraulic fluid from the hydraulic pump, regardless of whether or not the bucket is in contact with the ground, and the lowering control during a normal working mode is performed in a valve passage state at the first region in a non-ground-contacting state and at a second region in which the hydraulic fluid can be supplied from the hydraulic pump in a ground-contacting state.

Boom control circuit for a construction machine

To enable to arbitrarily change a hydraulic pump which supplies pressure oil to a hydraulic actuator at first in a hydraulic control system equipped with the hydraulic actuator using both first and second hydraulic pumps as a pressure oil source. An operation means is installed which can arbitrarily change working order of the first flow rate control valves for boom and stick for controlling the supply flow rate from first hydraulic pump to boom cylinder and stick cylinder and second flow rate control valves for boom and stick for controlling the supply flow rate from second hydraulic pump to boom cylinder and stick cylinder.

Hydraulic control system for a working machine

To provide a drift-prevention valve device, a blade device, and a working machine capable of operating an actuated unit and preventing the machine body from drifting with a simple configuration. The drift-prevention valve device is provided with a non-return valvethat allows the flow of hydraulic oil from a control valveto a head chamberof a blade cylinderand blocks the flow of the hydraulic oil in the reverse direction; and a piston accommodation partseparately disposed from an accommodation partof the non-return valve, configured to movably accommodate a power piston. The power pistondefines a first piston chambercommunicating with a rod chamber ofof the blade cylinderand a second piston chamberfor drain positioned on a poppetside of the non-return valveand communicating with a tank. The power pistonis connected to the poppetof the non-return valve, so that the power pistoncan be operated by the difference between the urging force of the poppetby a springof the non-return valveand a rod chamber pressure of the blade cylinder

Drift-prevention valve device, blade device, and working machine

To improve operability and work efficiency while achieving reduction of the number of parts and simplification of circuit structure, in a hydraulic control system equipped with hydraulic actuators whose hydraulic power sources are both the first, second hydraulic pumps. The hydraulic control system is provided with the stick directional switching valve; the main-side, sub-side supply oil passages connecting the hydraulic pumps to the stick directional switching valve; and the stick flow rate control valve which is placed in the sub-side supply oil passage, and controls the supply flow rate from the hydraulic pump when the supply flow rate to the stick cylinder requires the supply flow rates from both the hydraulic pumps, wherein the stick directional switching valve is configured such that the discharge flow rate control is performed in the entire area of the spool stroke, and the supply flow rate control is performed at the first region of the former half of the spool stroke, but not performed at the second region of the latter half of the spool stroke.

To make it possible to control supply, discharge, and recycled flow rates independently of each other for the stick cylinder in a construction machine comprising first and second stick spool valves respectively connected to first and second hydraulic pumps. [Solution] A poppet valve is provided at upstream side of the first stick spool valve for controlling a supply flow rate from first hydraulic pump, the first stick spool valve is configured to supply hydraulic flow from the poppet valve to the stick cylinder without restricting the flow, and when the stick cylinder is extended, the poppet valve is configured to control supply flow rate from the first hydraulic pump to head side oil chamber, the first stick spool valve is configured to control recycled flow rate from a rod side oil chamber to the head side oil chamber, and the second stick spool valve is configured to control the supply flow rate from second hydraulic pump to head side oil chamber and the discharge flow rate from the rod side oil chamber to an oil tank.

Hydraulic control circuit for a construction machine

To make it possible to control supply, discharge, and recycled flow rates independently of each other for the boom cylinder in a construction machine comprising first and second boom spool valves respectively connected to first and second hydraulic pumps. When the boom cylinder is contracted, the first boom spool valve is configured to control the recycled flow rate from head side oil chamber to rod side oil chamber, the second boom spool valve is configured to control the discharge flow rate from head side oil chamber to oil tank, and both first and second boom spool valves are configured not to supply pressure oil from first and second hydraulic pumps to the boom cylinder.

It is to provide a control valve that can make the valve body smaller and the structure simplified and the hydraulic pressure system equipped therewith. The plural number of parallel feeder oil paths that are respectively connected to the plural number of pumps and are not cut off by displacement of spools is provided in the valve body in a linearly through all spool holes. For each section, a connection oil path is provided to connect any one side of parallel feeder oil paths to the bridge circuit B of the internal spools. Parallel feeder oil paths can be positioned in a simple shape, but also, just by properly providing connection oil paths, without depending on each section belonging to any of pump systems, positioning of section can be freely done within the valve body. Making the valve body smaller and the structure simplification can be executed.

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Akashi, Japan

Koichi Kiyasu