JPH04256697A - Fork lift control device - Google Patents

Abstract

PURPOSE:To provide possibility of safely handling a fragile object without risk of breakage by permitting a fork to land without impact. CONSTITUTION:The lift of a fork is sensed by a position sensor, and the fork falling speed is decreased gradually when the fork is going to land, or it is allowed to fall at a very low speed. Thereby the fork will land automatically without impact. This should reduce burden on the operator and prevent breakage of object handled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a forklift that can perform cargo handling using an electromagnetic hydraulic system, and has been improved so that particularly fragile cargo can be safely landed.

0002

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated in an electrohydraulic manner, for example, the one shown in FIG. As shown in the figure, hydraulic pressure from a hydraulic pump 101 is divided into an electromagnetic proportional control valve 102 and a power steering control valve (not shown). Electromagnetic proportional control valve 102
An oil chamber 102a for pilot operation is formed in the oil chamber 102a, and a pilot piston 102b is slidably fitted into this oil chamber 102a. This pilot piston 102
b is connected to a spool 102c that switches the oil path. Pilot piston 102b and spool 102c
are connected to springs 103a and 103b, respectively, and are held at a neutral position without hydraulic pressure. Pilot inflow pipes 10 are provided on both sides of the pilot piston 102b.
2d and 102e are provided, respectively. The pilot inflow pipes 102d and 102e are equipped with electromagnetic on-off valves 102f,
It is connected to the power steering hydraulic system via 102g. Therefore, by opening and closing the electromagnetic on-off valves 102f and 102g, the pilot piston 102b and the spool 102c move from side to side in the figure. Spool 102
When c moves, pressure oil is supplied to and discharged from the work machine cylinder 104 via this spool 102c, and the work machine cylinder 10
4 expands and contracts. Depending on the movement position of the spool 102c, the flow rate of the pressure oil supplied to and discharged from the working machine cylinder 104 is adjusted, and its lifting speed is adjusted. As the working machine cylinder 104, various types can be used, such as one that raises and lowers a fork (not shown), one that tilts it, and the like.

On the other hand, the opening and closing of the electromagnetic on-off valves 102f and 102g are controlled by a flow rate control signal from a controller 105. The controller 105 is a work machine lever 106
A flow rate control signal is output based on the lever operation signal from. The work machine lever 106 includes a potentiometer and outputs a lever operation signal according to the tilt angle and the tilt direction. The work implement lever 106 does not output any output in the neutral position. Therefore, by operating the work machine lever 106,
Pressure oil is supplied and discharged from the electromagnetic proportional control valve 102 to the working machine cylinder 104 by opening and closing the electromagnetic on-off valves 102f and 102g,
When the work machine cylinder 104 expands and contracts to lift, lower, tilt, etc. the fork, and adjust the inclination angle of the work machine lever 106, the flow rate of pressure oil to the work machine cylinder 104 is adjusted, freely controlling the lifting speed, etc. be able to.

0004

[Problems to be Solved by the Invention] During cargo handling operations using a forklift, if a load lifted by a fork is simply lowered and landed on the ground, a shock is applied to the load upon landing. For this reason, when handling fragile items such as bottles and roof tiles, there is a risk of damage due to impact upon landing. For this reason, just before the fork touches down, the operator returns the work equipment lever to the neutral position to stop the fork from descending, and then reduces the inclination angle of the work equipment lever to slowly bring the fork into contact with the ground through an inching motion. , so as not to cause any shock. However, it is a troublesome task for the operator to temporarily stop the fork in the middle of its descent and then perform an inching operation, and requires skill. Furthermore, the heavier the load, the lower the load must be to lower the load in order to avoid impact, which is a time-consuming task even for experienced operators. The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a forklift control device that improves work efficiency and allows cargo handling operations to be performed without damaging fragile objects.

[0005]

[Means for Solving the Problems] A first configuration of the present invention that achieves the above object includes a controller that outputs a flow rate control signal to an electromagnetic proportional control valve in response to a lever operation signal from a work equipment lever, and the controller. an electromagnetic proportional control valve that supplies and discharges pressure oil to the work equipment cylinder according to a flow rate control signal from the
A forklift including a work equipment cylinder that expands and contracts with pressure oil from the electromagnetic proportional control valve to raise and lower the fork, a position sensor that detects when the lift height of the fork becomes below a certain level; an oil pressure sensor that detects the load of the cargo loaded on the fork from the oil pressure of pressure oil supplied and discharged from the fork, and a load that converts the larger the load detected by the oil pressure sensor into a smaller positive deceleration control amount. a deceleration control amount conversion table; a deceleration control amount calculating means for asymptotically subtracting the deceleration control amount converted by the table from the flow rate control signal and outputting the result; The present invention is characterized by further comprising a control amount output means for outputting the calculated value calculated by the amount calculation means as a flow rate control signal to gradually reduce the downward speed of the fork. A second configuration of the present invention that achieves the above object includes a controller that outputs a flow rate control signal to an electromagnetic proportional control valve in response to a lever operation signal from a work equipment lever; In the forklift, the forklift is equipped with an electromagnetic proportional control valve that supplies and discharges pressurized oil to and from a work equipment cylinder, and a work equipment cylinder that expands and contracts with the pressure oil from the electromagnetic proportional control valve to raise and lower the fork. a position sensor that detects that the pressure has fallen below a certain level; a hydraulic pressure sensor that detects the load of the load loaded on the fork from the hydraulic pressure of pressure oil supplied and discharged to the working machine cylinder; A load/deceleration control amount conversion table that converts the larger the load into a smaller positive deceleration control amount, and a deceleration control amount that asymptotically subtracts the deceleration control amount converted from the table from the flow rate control signal and outputs the result. a calculating means, a slow speed control amount outputting means for outputting a slow speed control amount that allows the load loaded on the fork to land without impact; and when the fork is detected by the position sensor, the deceleration control amount calculating means The descending speed of the fork is gradually decelerated by outputting the calculated value as a flow control signal, and when the calculated value becomes equal to the fine speed control amount, the fine speed control amount is output as a flow rate control signal and the The present invention is characterized in that it is provided with a control amount output means for lowering the fork at a very slow speed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings. An embodiment of the present invention is shown in FIGS. 1 to 4. FIG. 3 is a perspective view showing an example of a forklift truck applied to this embodiment. As shown in the figure, the lift cylinder 1 is fixed to a pair of left and right outer masts 2, and as the piston rod 1a expands and contracts, the pair of left and right inner masts 3 is raised and lowered using the outer masts 2 as a guide. At this time, the outer mast 2 is fixed to the vehicle body 7 in front of the vehicle body 7. As a result, inner mast 3
As the truck moves up and down, the lifting section consisting of a bracket 5 suspended on a chain and a fork 4 for directly loading cargo moves up and down. The tilt cylinder 8 is used to tilt the elevating section together with the outer mast 2 and the inner mast 3 forward (toward the vehicle body 7 side) and rearward (toward the vehicle body 7 side). That is, it tilts forward when unloading, and tilts backward when lifting or transporting cargo, thereby maintaining good workability and ensuring safety.

The work equipment levers 9a and 9b are operated by an operator to control the operation of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11, and are used to perform an emergency stop. It is housed in a joystick box 13 along with a safety switch 12 for carrying out the operation. Work machine levers 9c, 9d, 9
e is various attachments, such as roll clamps,
This is for when a bail clamp or the like is installed. The seat switch 14 is a switch that operates when an operator sits on the driver's seat 15, and its output signal is output to the controller 10. FIG. 4 is a block diagram showing an example of the forklift control device. As shown in the figure,
The work equipment levers 9a and 9b are formed by potentiometers, and a lever operation signal S1 whose current value is proportional to the operation amount
is sent to the controller 10. The controller 10 sends out a flow rate control signal S2 that adjusts the opening degree of the spool of the electromagnetic proportional control valve 11 based on the lever operation signal S1. The electromagnetic proportional control valve 11 moves the spool in proportion to the magnitude of the flow rate control signal S2, controls the flow rate of the pressure oil flowing through the hydraulic line 16, and adjusts the operating speed of the lift cylinder 1 and tilt cylinder 8 to the working machine. Control is performed to correspond to the amount of operation of the levers 9a and 9b.

The oil pressure sensor 17 is disposed in the oil pressure line 16 and sends out an oil pressure signal S3 representing the oil pressure in the oil pressure line 16. The controller 10 processes the hydraulic signal S3 to calculate the load acting on the lift cylinder 1 and the tilt cylinder 8. Further, the controller 10 operates by being supplied with power from the battery 21 when a starter switch 20, which is housed in a console box 19 together with a warning light 18, is turned on, and when the safety switch 12 is operated and the seat switch 14 is not operated. When the person is away from the seat, the current value of the flow rate control signal S2 is set to zero, and the opening degree of the electromagnetic proportional control valve 11 is controlled to be zero. In the figure, 22 is a hydraulic pump, and 23 is a hydraulic oil source. Further, the number of hydraulic components such as the electromagnetic proportional control valve 11, the hydraulic conduit 16, and the hydraulic pressure sensor 17 is provided in a number corresponding to the number of work machine levers 9a to 9e. In this embodiment, two working machine levers 9a and 9b are provided for lifting and tilting, so that two hydraulic systems may be provided.

FIG. 1 shows the main parts of a forklift control device according to an embodiment of the present invention. As shown in the figure, the controller 10 of this embodiment includes a control amount extraction means 25
, manipulated variable/controlled variable correspondence table 26, controlled variable output means 2
It has 7. In the operation amount/control amount correspondence table 26, a lever operation signal S1 of the work implement lever 9a and a flow rate control amount S2 are stored in correspondence. Therefore, a flow rate control amount S2 corresponding to the inclination direction and inclination angle of the work implement lever 9a is extracted by the control amount extraction means 25, and outputted to the electromagnetic proportional control valve 11 by the control amount output means 27. Further, the controller 10 includes a deceleration control amount calculation means 28, a load/deceleration control amount correspondence table 29, a determination means 30, a slow speed control amount extraction means 31, and a load/low speed control correspondence table 32.
and storage means 33. The load/deceleration control amount correspondence table 29 is a table in which the oil pressure detected by the oil pressure sensor 17, that is, the value corresponding to the load of the load placed on the fork, and the deceleration control amount are stored in correspondence. The larger the value, the smaller the deceleration control amount. The deceleration control amount is a temporal change in the flow rate control amount to obtain the necessary deceleration, and as shown in FIG. 6, the larger the load of the cargo, the smaller the value becomes. This is because the larger the load, the smaller the deceleration, so that the load is stabilized and there is no impact. Note that the deceleration control amount is a positive value. The deceleration control amount calculating means 28 converts the deceleration control amount extracted from the load/deceleration control amount correspondence table 29 into the current flow rate control amount S2.
The result is repeatedly subtracted from , and output to the determining means 30 . For example, if the current flow rate control amount S2 is 500 mm
/sec, and the deceleration control amount is 50m
m/sec, 450mm/sec
c, 400mm/sec, 350mm/sec...
Calculated values corresponding to are output in order.

The load/low speed control correspondence table 32 is a table in which the oil pressure detected by the oil pressure sensor 17, that is, a value corresponding to the load of the load placed on the fork, and the slow speed control amount are stored in correspondence. The slow speed control amount extraction means 31 outputs the slow speed control amount extracted from the load/slow speed control correspondence table 32 to the determining means 30. The slow speed control amount is the amount of flow control necessary to reach the slow speed, and the slow speed is the descending speed that is slow enough to allow the load loaded on the fork to land without impact. . Generally, as shown in FIG. 7, the larger the load, the smaller the slow velocity is desirably. This is because the larger the load, the more likely an impact will occur unless it descends at a low speed. The determining means 30 is
The (current flow rate control amount S2 - deceleration control amount) calculated by the deceleration control amount calculation means 28 and the slow speed control amount extraction means 31
The control amount is compared with the slow speed control amount input from the control amount output means 27, and the larger one is selectively outputted to the control amount output means 27. That is, when the calculated value obtained by subtracting the deceleration control amount extracted from the load/deceleration control amount correspondence table 29 from the current flow rate control amount S2 is larger than the slow speed control amount, the calculated value is output and (the current flow rate control amount S2 When S2 - deceleration control amount) is less than or equal to the fine speed control amount, the fine speed control amount is output.

The controlled variable output means 27 is the controlled variable extracting means 2.
Either the flow rate control amount S2 inputted from 6 or the (current flow rate control amount S2 - deceleration control amount) inputted from the determining means 30 or the slow speed control amount is selectively subjected to electromagnetic proportional control by the detection signal from the position sensor 24. Output to valve 11. That is,
A position sensor 24 is provided on the work machine cylinder 1, and this position sensor 24 detects a certain lift height immediately before the fork lands. The constant lift height is, for example, about 30 cm above the ground. Until the position sensor 24 detects a certain lift height just before the fork lands, the controlled amount output means 27 outputs the flow rate control amount S2 from the controlled amount extraction means 26 to the electromagnetic proportional control valve 11. When the sensor 24 detects that the lift height is below the certain level, the O
When N is reached, the determination circuit 30 outputs (current flow rate control amount S2 - deceleration control amount) to slow speed control amount to the electromagnetic proportional control valve 11. Hereinafter, control based on the slow speed control amount or the deceleration control amount will be referred to as soft touch control. Note that a mode changeover switch may be provided that always outputs the flow rate control amount S2 from the control amount extraction means 26 with priority, regardless of whether the position sensor 24 detects it or not.

Specifically, in this embodiment having the above configuration, a forklift is controlled according to the flowchart shown in FIG. First, after initialization, it is determined whether the work implement lever is in the neutral position. When the work equipment lever is in neutral, neutral control is performed to maintain the fork at a constant height, and when the work equipment lever is not neutral and has been knocked down, lift up control to raise the fork or lift down control to lower the fork is performed. . In the case of lift lowering control, when the position sensor 17 is turned on and it is detected that the lift height is below a certain level, soft touch control is performed. That is, when the position sensor 24 is turned on and it is detected that the height of the fork has become below a certain level, the deceleration control amount calculating means 28 reads out the deceleration control amount from the load/deceleration control amount correspondence table 29 and performs slow speed control. The load/
The slow speed control amount is read from the slow speed control table 32. At the same time, a mode is set to indicate soft touch control. The deceleration control amount and slow speed control amount both correspond to the load of the cargo, so when controlled using soft touch control, the larger the load, the gentler the slope of the descending speed change curve, as shown in Figure 8. Become. However, in the case of deceleration control, the change in the slope is large, but in the case of slow speed control, the change in the slope is minute.

After that, after confirming that the soft touch mode is set, the extracted deceleration amount is repeatedly subtracted from the previous flow rate control amount S2, and this calculated value is used as the current flow rate control amount. Output. This calculated value is applied to the electromagnetic proportional control valve 11 until this calculated value becomes equal to the slow speed control amount.
Output to. For this reason, the descending speed of the fork gradually slows down, resulting in a curve as shown in FIG. Then, the descending speed becomes equal to the very low speed, that is, the speed becomes low enough to allow the cargo to land without impact. In this way, when (current flow rate control amount S2 - deceleration control amount) becomes smaller than the slow speed control amount, the slow speed control mode is set and the slow speed control amount is output in place of the above value. Therefore, as shown in FIG. 8, the fork then descends at a constant speed, allowing the load to land safely without impact.

[0014] In this way, in the above embodiment, the descending speed of the fork can be automatically decelerated to a very low speed that allows the fork to land on the ground without impact, and furthermore, the deceleration is adjusted according to the load of the cargo, so that there is no damage to the cargo. Never give up. Furthermore, since the speed is gradually reduced to a very low speed instead of suddenly decelerating or stopping, the load on the fork does not lose its balance and there is no risk of it falling. Further, since no operation is required by the operator, labor is reduced. Incidentally, in the above embodiment, the minute velocity was changed depending on the load of the cargo, but it may be constant regardless of the load as long as it is possible to land without impact. Alternatively, the speed may be decelerated until the descending speed reaches zero without setting the slow speed. In particular, in the case of fragile cargo, it is necessary to suppress not only the shock but also the vibration when landing. In this case, it is better to interrupt the descent and then resume the descent slowly. Safe control.

[0015]

[Effects of the Invention] As described above in detail based on the embodiments, the present invention performs deceleration control to automatically gradually decelerate when the fork descends and becomes below a certain lifting height. The deceleration is adjusted according to the load of the cargo. Therefore, even heavy loads can be landed without impact.
It's safe. Furthermore, up to a certain height, the descending speed can be increased, improving work efficiency.
Furthermore, since the operator does not need to operate any levers of the working machine, the amount of labor required is reduced. Furthermore, if the slow speed control is performed in which the robot decelerates to a very low speed that allows the robot to land without impact, and then descends at the same low speed without decelerating any further, there is an advantage that the aircraft can land efficiently and without impact.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of an embodiment of the present invention.

FIG. 2 is a flowchart showing the steps of an embodiment of the present invention.

FIG. 3 is an external perspective view of a forklift to which the present invention is applied.

FIG. 4 is a block diagram showing the overall configuration of a forklift control device according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional forklift control device.

FIG. 6 is a graph showing the relationship between deceleration amount and load.

FIG. 7 is a graph showing the relationship between slow speed and load.

FIG. 8 is a graph showing lowering control of the fork.

[Explanation of symbols]

1 Lift cylinder 1a Piston rod 2 Outer mast 3 Inner mast 4 Fork 5 Bracket 10 Controller 11 Electromagnetic proportional control valve 14 Seat switch 16 Hydraulic line 17 Oil pressure sensor 24 Position sensor 25 Controlled amount extraction means 26 Manipulated amount/controlled amount correspondence table 27 Control amount output means 28 Deceleration control amount extraction means 29 Load/deceleration control amount correspondence table 30 Judgment means 31 Slow speed control amount extraction means 32 Load/slow speed control amount correspondence table 33 Storage means S1 Lever operation signal S2 Flow rate control signal

Claims (2)

[Claims] [Claim 1] A controller that outputs a flow rate control signal to an electromagnetic proportional control valve in accordance with a lever operation signal from a work equipment lever, and supplies and discharges pressure oil to and from a work equipment cylinder in accordance with the flow rate control signal from the controller. In a forklift equipped with an electromagnetic proportional control valve and a working machine cylinder that expands and contracts with pressure oil from the electromagnetic proportional control valve to raise and lower the fork, a position sensor detects when the lift height of the fork falls below a certain level. and an oil pressure sensor that detects the load of the load loaded on the fork based on the oil pressure of pressure oil supplied and discharged to the working machine cylinder, and a positive deceleration control that decreases as the load detected by the oil pressure sensor increases. a load/deceleration control amount conversion table for converting into a quantity, a deceleration control amount calculation means for repeatedly subtracting the deceleration control amount converted by the table from the flow control signal and outputting the result, and the fork being detected by the position sensor. and control amount output means for outputting the calculated value calculated by the deceleration control amount calculation means as a flow rate control signal to gradually decelerate the descending speed of the fork. [Claim 2] A controller that outputs a flow rate control signal to an electromagnetic proportional control valve in accordance with a lever operation signal from a work equipment lever, and supplies and discharges pressure oil to and from a work equipment cylinder in accordance with the flow rate control signal from the controller. In a forklift equipped with an electromagnetic proportional control valve and a working machine cylinder that expands and contracts with pressure oil from the electromagnetic proportional control valve to raise and lower the fork, a position sensor detects when the lift height of the fork falls below a certain level. and an oil pressure sensor that detects the load of the load loaded on the fork based on the oil pressure of pressure oil supplied and discharged to the working machine cylinder, and a positive deceleration control that decreases as the load detected by the oil pressure sensor increases. a load/deceleration control amount conversion table for converting into a quantity; a deceleration control amount calculation means for asymptotically subtracting the deceleration control amount converted by the table from the flow rate control signal and outputting the result; and a load loaded on the fork. a slow speed control amount output means for outputting a slow speed control amount that allows the fork to land without impact; and when the fork is detected by the position sensor, the calculated value calculated by the deceleration control amount calculation means is outputted as a flow rate control signal. By doing so, the descending speed of the fork is gradually decelerated, and when the calculated value becomes equal to the slow speed control amount, the slow speed control amount is outputted as a flow rate control signal to lower the fork at a slow speed. A forklift control device characterized by being provided with.