Motors: expansible chamber type – Working member position feedback to motive fluid control – Electrical input and feedback signal means
Patent
1994-07-20
1996-04-30
Lopez, F. Daniel
Motors: expansible chamber type
Working member position feedback to motive fluid control
Electrical input and feedback signal means
91397, F15B 1316
Patent
active
055114580
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an automatic cushioning control apparatus for a hydraulic cylinder of a construction equipment working machine such as a hydraulic shovel, wheel loader, and the like.
BACKGROUND ART
Conventionally, construction equipment, which has a working machine such as a hydraulic shovel driven by a hydraulic cylinder, is provided with a mechanical cushion to ease a shock at a stroke end of a cylinder, the shock being caused when an operator operates a lever. If the lever is fully moved, hitting the stroke end, a conventional mechanical cushion cannot completely absorb the inertial force of the working machine, and a big noise is produced at the time of the collision, causing the vehicle body to shake. In addition, a cushion chamber is subjected to a high back pressure, adversely affecting the durability of the cylinder and also leading to higher structural cost. To solve these problems; detected so that, when a dangerous zone set near the end of the stroke path is reached, the engine RPM or the angle of a swash plate is decreased to reduce the discharge quantity of a pump, thereby decreasing the speed of the cylinder, and set back to the neutral to stop the cylinder (refer to the Japanese Published Unexamined Patent Application No. 2-57703).
They have, however, disadvantages described below:
(1) The method, wherein the engine RPM or the discharging quantity of the pump is reduced, prevents satisfactory composite operation because an engine pump is not provided on each shaft of the working machine, and therefore, each time one shaft reaches a stroke end, the working speed of other shafts unavoidably decreases. There is another disadvantage in that the engine or the pump is required to exhibit extremely high responsiveness.
(2) The method, wherein the cylinder control valve is set back to the neutral, is disadvantageous in that, when the cylinder length reaches the dangerous zone, a controller issues a signal for setting the valve back to the neutral independently of the lever operation performed by an operator, thus carrying out automatic deceleration irrespectively of operator's intent.
In general, when operating a shaft with high inertia at a full lever stroke, the dangerous zone must be secured with a certain level of ampleness in order to stop the shaft without causing a shock at a stroke end. Such conventional methods, however, make it difficult for the operator to stop the cylinder in a desired position within the dangerous zone, thus narrowing the zone for operating the working machine, wherein the operator can operate it.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the problems with the conventional methods, and it is an object of the present invention to provide an automatic cushioning control apparatus for a cylinder of a working machine, which is capable of providing cushioning effect for minimizing noises and shaking of a vehicle body by ensuring adequate deceleration at the time of cushioning to avoid generating high pressure, without using a mechanical cylinder cushion, and which also contributes to high durability of the cylinder main body.
In construction equipment having a working machine driven by a working machine hydraulic cylinder, the present invention has a cylinder position detecting means for detecting the position of a working machine cylinder along the stroke path thereof in the direction of a stroke thereof, a moving direction detecting means for detecting the direction of extending and retracting movement of the working machine cylinder along the stroke path, a lever gain computing means for computing lever gain K with respect to a lever signal from a lever device, which is adapted to satisfy a relationship, 0<K<1, in accordance with signals from the aforesaid cylinder position detecting means and the moving direction detecting means, and which gradually changes from one toward zero in accordance with the distance to a stroke end when the cylinder is moving toward the stroke end, a multiplica
REFERENCES:
patent: 4350078 (1982-09-01), Olofsson
patent: 4358989 (1982-11-01), Tordenmalm
patent: 4733600 (1988-03-01), Masano
patent: 4896582 (1990-01-01), Tordenmalm et al.
Kamata Seiji
Kuromoto Kazunori
Kabushiki Kaisha Komatsu Seisakusho
Lopez F. Daniel
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