Control system for lowering forklift lever
A system of controlling a lowering speed of a work lever of a forklift which includes, a hydraulic motor connected to the work lever through a hydraulic line to transmit a power to the work lever; an electronic solenoid valve for controlling the hydraulic motor connected to the work lever; a weight sensor provided at one side of the work lever, the weight sensor measuring a weight of a load placed on the work lever and transmitting the measured value to a controller; and a controller for controlling an RPM of the hydraulic motor and a current amount of the electronic solenoid valve based on the measured value transmitted from the weight sensor.
1. A system of controlling a lowering speed of a work lever of a forklift, comprising:
a hydraulic motor connected to the work lever through a hydraulic line to transmit a power to the work lever;
an electronic solenoid valve configured to control the hydraulic motor connected to the work lever;
a weight sensor provided at one side of the work lever, the weight sensor configured to measure a weight of a load placed on the work lever, to convert the weight into a load voltage, and to transmit the load voltage corresponding to a measured value to a controller; and
a controller configured to control an RPM of the hydraulic motor and to control a current amount applied to the electronic solenoid valve based on a maximum current determined with respect to the measured value transmitted from the weight sensor, such that a rate of change in a lowering speed of the work lever is unaffected by the weight of the load placed on the work lever,
wherein the controller includes a preset table in which is stored a maximum current under a full load condition and a maximum current under a no-load condition that represent the determined maximum current for those respective conditions, and
wherein the controller is configured to determine the maximum current where the work lever has a load less than a full load, between the maximum current under the full load condition and the maximum current under the no-load condition, according to the load voltage transmitted by the weight sensor.
2. The system of claim 1 , wherein the controller determines the maximum load current of the electronic solenoid valve based on the load voltage and the following equation:
H
=
(
B
-
C
)
(
E
-
D
)
×
(
G
-
D
)
+
C
where: B is the maximum current under full load condition, C is the maximum current under no-load condition, D is a minimum weight voltage, E is a maximum weight voltage, G is the load voltage, and H is the determined maximum load current.
3. The system of claim 2 , wherein a table according to a height of a work machine operation device is preset in the controller, and
the controller determines a valve current applied to the electronic solenoid valve, based on the determined maximum load current.
4. The system of claim 3 , wherein the controller determines the valve current based on the following equation:
I
=
A
+
F
1000
×
(
H
-
A
)
where A is the minimum current, D is the minimum weight voltage, F is a height value in a range of 0-1000 corresponding to the height of the work machine operation device, H is the determined maximum load current, and I is the valve current.