Power plants – Pressure fluid source and motor – Condition responsive control of or by input to input pump...
Reexamination Certificate
2001-09-20
2003-05-20
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of or by input to input pump...
C060S452000, C091S453000
Reexamination Certificate
active
06564548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a speed control apparatus of a working vehicle such as a vehicle for a construction, civil engineering work and the like, which is provided with a crane function, and a speed control method thereof. More particularly, it relates to a speed control apparatus of a working vehicle which can adjust a working speed of a working machine and a traveling speed of the vehicle within a predetermined speed range under a crane mode so as to improve a working efficiency, and a speed control method thereof.
2. Description of the Related Art
A working vehicle for various kinds of construction, civil engineering machines and the like is provided with a working machine comprising a revolving frame mounted onto an undercarriage so as to freely revolve around a vertical axis, and a main boom, a stick boom, a bucket, a suspending hook and the like mounted on the revolving frame. A discharged pressure oil supplied from a variable delivery pump is supplied to a main boom cylinder, a stick boom cylinder, a bucket cylinder, a revolving motor, a traveling motor and the like, whereby the working vehicle drives or travels each of the working machines.
An example of the working vehicle mounted with such actuators is disclosed, for example, in Japanese Patent No. 2863599. A hydraulic working machine as disclosed in the publication is provided with an accelerator lever for setting an engine speed, an engine-speed command transmitting device for detecting an amount of operation of the accelerator lever so as to output an engine speed command signal in correspondence to the amount of the operation, engine speed setting means for increasing and reducing the engine speed, flow amount adjusting means for increasing and reducing a pump flow amount of a variable delivery pump, a relief valve for setting a maximum operating pressure in a discharge side of the pump, and relief pressure setting means for setting a maximum pressure of a pressure oil introduced to actuators for a working machine.
Further, the hydraulic working machine is provided with working mode selecting means, which previously stores various kinds of working modes such as a working mode for working the actuators at a high speed, a working mode for executing a precise work and the like, in addition to a combination of an application force and a working speed of the actuators required for a normal work, in order to freely select the working mode.
When an operator selects a desired working mode by the working mode selecting means in correspondence to working contents and working conditions to be executed, the working mode selecting means selects at least one of a maximum engine speed, a maximum discharge flow amount of the pump and a maximum pressure of the pressure oil introduced to the working machine actuators, which are previously stored for each selected working mode, and outputs as a working mode command signal to a controller.
The controller receives the working mode command signal from the working mode selecting means and the engine speed command signal from the engine speed command transmitting device, and suitably selects the maximum engine speed among the working mode command signal and the engine speed command signal so as to output the command signal to the engine speed setting means. At the same time, the controller outputs the command signal to the pump flow amount adjusting means on the basis of the working mode command signal, and outputs the command signal to the relief valve and the relief pressure setting means.
In the manner as mentioned above, the controller outputs the command signal to the flow amount adjusting means and the engine speed setting means such that the working speed of the actuators operated on the basis of the command signal output from the controller is neither too much nor too little, thereby controlling the discharge oil amount of the variable delivery pump. At the same time, the controller outputs the command signal to the relief valve and the relief pressure setting means so that a working force of the actuator is neither too much nor too little, thereby controlling the pressure of the pressure oil flowing into the actuator.
In accordance with the conventional hydraulic working vehicle, the flow amount and the maximum pressure of the pressure oil flowing into the actuators are automatically restricted by the engine speed setting means, the flow amount adjusting means, the relief pressure setting means and the like. Accordingly, it is possible to obtain the working speed and the application force, which are optimum for the working contents and the working conditions of the selected working mode.
On the other hand, in this kind of working vehicle, a working speed of a main boom cylinder and a stick boom cylinder at the time of normal excavating operation, a dumping operation or the like is set such that, for example, a speed at the time of ascending the main boom and the stick boom is about 30% of a speed at the time of descending them. This can be applied in the same manner even to a hydraulic working vehicle having a crane function, in which a suspending hook is mounted to a stick boom front end portion of a normal working vehicle. Even when it is switched to a crane mode, an ascending speed of a peripheral portion of the suspending hook is widely delayed in comparison with a descending speed thereof.
The hydraulic working machine disclosed in the patent publication mentioned above previously expects various kinds of preferable working modes corresponding to various kinds of driving and operating conditions, and stores them in the working mode selecting means. However, these working modes are selected by the operator himself on the basis of his/her sense and judgement with respect to environmental conditions immediately before starting the operation, even when the working contents and the working conditions have changed. For example, under a condition that various environments such as a change in the weather, a change in the working range, with or without an obstacle and the like are generated, an operation of the set working mode does not always coincide with an actually executed working condition.
The controller only uniformly outputs the command signal corresponding to the set working mode to the engine, the variable delivery pump, the relief valve and the like. Thus, once a certain mode is set, it is impossible to change the set working speed and the set working pressure of the working machine in the working mode, even in the case that a change has been generated in the executed working contents or the working conditions. Accordingly, in the case that the preset working mode does not comply with the actual working condition, or in the case that it is not a mode that can correspond to a skill of the operator, the operation has to be executed within the working mode range. Therefore, a working efficiency or the like is easily reduced.
In particular, in the working vehicle provided with the crane function, since the operation is executed in a state that the descending speed of the periphery of the suspending hook and the ascending speed thereof are widely different from each other, as in the same manner as that at the normal excavating time as mentioned above, even when it is switched to the crane working mode. Therefore, the operator who operates the crane within a cab can not be used to the speed difference, so that he/she can hardly expect the switching timing between the ascending operation of the suspended load and the descending operation thereof, whereby a working efficiency is going to be reduced.
SUMMARY OF THE INVENTION
The present invention is made in order to solve the conventional problems. An object of the present invention is to provide a speed control apparatus of a working vehicle which can reduce a working speed of a working machine and a traveling speed of a vehicle to a desired speed range in correspondence to a change of working contents and working conditions at the time of executing a crane operati
Nagahara Takumi
Nishimura Satoru
Komatsu Limited
Lazo Thomas E.
Look Edward K.
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