In the drawing:
a is a schematic circuit diagram of an alternate embodiment of the hydraulic arrangement of
Illustrated in
The extension arm 14 is configured as a telescopic extension arm and is adjustably linked via a hydraulic cylinder 24 in respect of its angle of attack in relation to the frame 12. A second hydraulic cylinder (not illustrated) is arranged in the interior of the extension arm 14 and permits the retraction and/or extension (telescoping) of the extension arm. A third hydraulic cylinder (not illustrated) is arranged on the free end of the extension arm 14 in the interior and permits the oscillation and/or tilting of a loading implement 26.
The loader 10 possesses a hydraulic source 28 and a hydraulic tank 30, which are arranged underneath the vehicle bodywork and serve the purpose of supplying the hydraulic components.
An operating device 34, in the form of a hydro-mechanical joystick, is arranged in a cab 32 and serves the purpose of actuating the hydraulic components. The hydraulic components are illustrated substantially in
A hydraulic arrangement 36 envisaged for the loader 10 is illustrated in
A load holding valve 44 is arranged in the supply line 40 associated with the chamber on the lifting side of the hydraulic cylinder 24. The load holding valve comprises a pressure-limiting valve 46 capable of being opened via control pressure lines 48, 50, which are connected to both supply lines 38, 40, as well as a check valve 52 arranged in a bypass line and opening in the direction of the hydraulic cylinder 24. The load holding valve 44 serves to ensure that, in the event of a pipe fracture on the lifting side of the hydraulic cylinder 24, no hydraulic fluid is able to escape and the hydraulic cylinder 24 maintains its position.
The control device 42 comprises three gate positions, one for lifting, one for lowering and one more for holding the hydraulic cylinders. The control device 42 is configured as a hydraulically actuated proportional valve and can be hydraulically actuated or adjusted via corresponding control pressure lines 54, 56. The control pressure in this case is generated by the hydro-mechanical operating device 34, which is executed as a joystick.
The operating device 34 possesses valves 58, 60 that are actuated mechanically, for example, by moving the joystick, which provides for the engagement or disengagement of the hydraulic pump 28 with or from the control pressure lines 54, 56. The mechanically actuated valves 58, 60 are preferably configured as pressure reduction valves. For example, a joystick or actuating lever present Oh the operating device 34 is pushed forwards, which results in the actuation of the valve 58. The control pressure line 56 is then subjected to a hydraulic pressure produced by the hydraulic pump 28, whereupon the control device 42 is displaced into its lifting position and the hydraulic cylinder 24 is filled with hydraulic fluid on the lifting side, that is to say it is extended. A corresponding actuation of the actuating lever in the opposite direction would cause actuation of the valve 60, whereupon the control pressure line 54 would be filled with hydraulic fluid and the control device 42 would be displaced into the lowering position, that is to say the hydraulic cylinder 24 would be retracted.
In the illustrative embodiment depicted in
Control of the overpressure valve 62 takes place through the electronic control unit 64, which for its part receives control signals from the load case sensor 66. Depending on the load condition, the sensor indicates a more or less critical load condition. As the critical load condition is approached, the control input transmitted by the electronic control unit 64 for adjusting the overpressure valve 62 is also strengthened, which then causes the valve to be increasingly opened, so that hydraulic fluid flows increasingly from the control pressure line 54 and the control pressure is reduced. The adjustment or the increase of the control input in this case preferably takes place proportionally to the signal provided by the sensor.
The load sensor 66 is preferably arranged on the rear axle 18 of the loader 10. For example, the sensor 66 is configured as a strain gauge and registers or records the deflection of the rear axle 18. It is then possible to arrive at a conclusion in respect of the application and removal of the load on the rear axle 18 from the signal values for the deflection. If the load on the rear axle 18 were to reduce increasingly, this can point to the existence of a critical load condition, namely at the latest if a load was no longer to be detected or indicated on the rear axle 18. In this case, the loader 10 begins to overturn. A similar approach is also conceivable for the front axle 16.
The illustrative embodiment depicted in
a depicts an alternate illustrative embodiment of the hydraulic arrangement, in which the control pressure line 54 is provided with an electro-hydraulic pressure reducing valve 62′, in conjunction with which the connecting line to the hydraulic tank 30, which is provided in the illustrative example for
Here, too, control of the overpressure valve takes place through the electronic control unit 64, which for its part receives control signals from a load case sensor 66. Depending on the load condition, the sensor 66 indicates a more or less critical load condition. As the critical load condition is approached, the control input transmitted by the electronic control unit 64 for adjusting the pressure reduction valve 62′ is also strengthened, which valve is then closed increasingly, so that the control pressure reduces. The adjustment for the increase of the control input in this case preferably takes place proportionally to the signal provided by the sensor.
The load sensor 66 is preferably also located on the rear axle 18 of the loader 10, in this case too, and is configured in an analogous manner to the illustrative embodiment depicted in
The illustrative embodiment depicted in
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
Number | Date | Country | Kind |
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10 2006 042 370.4 | Sep 2006 | DE | national |