JP2706381B2 - Forklift control device - Google Patents

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 capable of operating a cargo operation by means of an electromagnetic hydraulic system, and more particularly, to a control device for safely landing fragile luggage.

[0002]

2. Description of the Related Art Conventionally, as a forklift control device which can be operated by an electromagnetic hydraulic system, for example, the one shown in FIG. 5 is known (Japanese Utility Model Laid-Open No. 60-107405). As shown in the figure, the hydraulic pressure from the hydraulic pump 101 is applied to the electromagnetic proportional control valve 102.
And a control valve (not shown) for power steering (not shown). An oil chamber 102 a for pilot operation is formed in the electromagnetic proportional control valve 102.
A pilot piston 102b is slidably fitted to 02a. The pilot piston 102b is connected to a spool 102c for switching an oil passage. The pilot piston 102b and the spool 102c are connected to springs 103a and 103b, respectively, and are held at a neutral position without hydraulic pressure. On both sides of the pilot piston 102b, pilot inflow pipes 102d, 1
02e are provided respectively. The pilot inflow pipes 102d and 102e are provided with electromagnetic on-off valves 102f and 102g.
Via a hydraulic system for power steering. Therefore, by opening and closing the electromagnetic on-off valves 102f and 102g, the pilot piston 102b and the spool 102c move right and left in the figure. When the spool 102c moves, pressure oil is supplied to and discharged from the working machine cylinder 104 via the spool 102c, and the working machine cylinder 104 expands and contracts. The flow rate of the pressure oil supplied to and discharged from the work machine cylinder 104 is adjusted by the moving position of the spool 102c, and the elevating speed is adjusted. As the work machine cylinder 104, various types such as a type that raises and lowers a fork (not shown) and a type that tilts the fork can be used.

On the other hand, the opening and closing of the electromagnetic on-off valves 102f and 102g is controlled by a flow control signal from a controller 105. The controller 105 includes a work implement lever 106
Outputs a flow control signal in response to a lever operation signal from the controller.
The work implement 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 power in the neutral position. Therefore, by operating the work implement lever 106, the electromagnetic on-off valves 102f and 102g are opened and closed, and pressure oil is supplied and discharged from the electromagnetic proportional control valve 102 to the work implement cylinder 104. Lifting,
When the inclination and the like are performed and the inclination angle of the work implement lever 106 is adjusted, the flow rate of the pressure oil to the work implement cylinder 104 is adjusted, and the elevating speed and the like can be freely controlled.

[0004]

In the loading operation of a forklift, if the load lifted by a fork is simply lowered to touch the ground, the load is impacted upon landing. For this reason, when handling fragile items such as bottles and roof tiles, there is a risk of damage due to impact at the time of landing. For this reason, immediately before the landing of the fork, the operator returns the work equipment lever to the neutral position and stops the lowering of the fork once.After that, the inclination angle of the work equipment lever is reduced and the fork is slowly grounded by the inching operation. , So as not to cause impact. However, temporarily stopping the lowering fork and then performing the inching operation is a complicated operation for the operator, and also requires skill.
Furthermore, the heavier the load, the lower it is necessary to lower at a low speed in order to prevent impact, and even a veteran operator takes a considerable amount of time. The present invention has been made in view of the above-described conventional technology, and has as its object to provide a control device for a forklift capable of improving work efficiency and performing cargo handling without breaking a fragile object.

[0005]

According to a first aspect of the present invention, there is provided a controller for outputting a flow control signal corresponding to a lever operation signal from a work implement lever to an electromagnetic proportional control valve, and the controller comprises: An electromagnetic proportional control valve for supplying and discharging pressure oil corresponding to the flow control signal from the work machine cylinder to the working machine cylinder;
In a forklift including a working machine cylinder that expands and lowers a fork by expanding and contracting with pressure oil from the electromagnetic proportional control valve, a position sensor that detects that the lift of the fork has become equal to or less than a certain value, and the working machine cylinder A hydraulic sensor for detecting the load of the load loaded on the fork from the hydraulic pressure of the pressure oil supplied and discharged to the fork; and a load / conversion to a smaller positive deceleration control amount as the load detected by the hydraulic sensor increases. A deceleration control amount conversion table, deceleration control amount calculation means for asymptotically subtracting the deceleration control amount converted from the table from the flow control signal and outputting the same, and the deceleration control when the fork is detected by the position sensor. Control amount output means for outputting the calculated value calculated by the amount calculation means as a flow control signal and gradually reducing the lowering speed of the fork. Characterized in that was. A second configuration of the present invention that achieves the above object includes a controller that outputs a flow control signal according to a lever operation signal from a work implement lever to an electromagnetic proportional control valve, and a controller that outputs a flow control signal from the controller. And a working machine cylinder that expands / contracts a fork by expanding and contracting with pressure oil from the electromagnetic proportional control valve. A position sensor for detecting that the pressure is below a certain level, a hydraulic sensor for detecting the load of the load loaded on the fork from the hydraulic pressure of the pressure oil supplied to and discharged from the working machine cylinder, and a hydraulic pressure sensor for detecting the load. A load / deceleration control amount conversion table for converting the load into a smaller positive deceleration control amount as the load increases, and a deceleration control amount converted from the table to the flow rate control. A deceleration control amount calculating means for asymptotically subtracting from the signal and outputting; a slow speed control amount output means for outputting a slow speed control amount capable of landing a load loaded on the fork without impact; and the position sensor. When the fork is detected, the calculated value calculated by the deceleration control amount calculation means is output as a flow control signal to gradually reduce the descending speed of the fork, and when the calculated value becomes equal to the slow speed control amount. And a control amount output means for outputting the slow speed control amount as a flow control signal and lowering the fork at a slow speed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. 1 to 4 show one embodiment of the present invention. FIG. 3 is a perspective view illustrating an example of a forklift applied to the present embodiment. As shown in the figure, the lift cylinder 1 is fixed to a pair of left and right outer masts 2, and the left and right inner masts 3 are raised and lowered by using the outer mast 2 as a guide as the piston rod 1a expands and contracts. 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 a result, the elevating unit including the bracket 5 suspended on the chain and the fork 4 for directly loading luggage moves up and down. The tilt cylinder 8 is for tilting the elevating unit forward (toward the vehicle body 7 side) and backward (to the vehicle body 7 side) together with the outer mast 2 and the inner mast 3. That is, in the case of unloading, it tilts forward and in the case of unloading and transports luggage, it tilts rearward, so that each workability is maintained well and safety is ensured.

The working machine 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 the emergency stop is performed. It is stored in a joystick box 13 together with a safety switch 12 for performing the operation. Work implement levers 9c, 9d, 9
e is various attachments, for example, a roll clamp,
This is to deal with the case where a bale clamp or the like is attached. The seat switch 14 is a switch that operates when the operator sits on the driver's seat 15, and outputs an output signal to the controller 10. FIG. 4 is a block diagram showing an example of the control device of the forklift. As shown in the figure,
The work implement levers 9a and 9b are formed by potentiometers, and a lever operation signal S ₁ whose current value is proportional to the operation amount.
Is sent to the controller 10. The controller 10
Sends a flow control signal S ₂ to adjust the degree of opening of the spool of the electromagnetic proportional control valve 11 on the basis of the lever operation signal S _1. The electromagnetic proportional control valve 11 moves the spool in proportion to the magnitude of the flow control signal S ₂ , controls the flow rate of the pressure oil flowing through the hydraulic line 16, and controls the lift cylinder 1 and the tilt cylinder 8.
Is controlled so as to correspond to the operation amount of the working machine levers 9a and 9b.

The hydraulic pressure sensor 17 is disposed in the hydraulic pressure line 16 and sends out a hydraulic pressure signal S ₃ representing the oil pressure in the hydraulic pressure line 16. The controller 10 processes the hydraulic signal S ₃ to calculate the load applied to the lift cylinder 1 and the tilt cylinder 8. Further, the controller 10 includes a warning light 18
When the starter switch 20 housed in the console box 19 is turned on, the power is supplied from the battery 21 to operate, and when the safety switch 12 is operated and when the seat switch 14 does not operate and the user is in the unattended state, the flow control signal S _The control is performed such that the current value of ₂ is set to zero and the opening of the electromagnetic proportional control valve 11 is set to zero. In the figure, 22
Is a hydraulic pump, and 23 is a hydraulic oil source. The hydraulic system components such as the electromagnetic proportional control valve 11, the hydraulic pipeline 16, the hydraulic sensor 17, and the like are provided in a number corresponding to the number of the working machine levers 9a to 9e. In the present embodiment, two working machine levers 9a, 9b for raising and lowering and tilting to perform the raising and lowering and tilting operations.
9b, two hydraulic systems may be provided.

FIG. 1 shows a main part of a forklift control apparatus according to one embodiment of the present invention. As shown in the figure, the controller 10 of the present embodiment is
5, an operation amount / control amount correspondence table 26 and a control amount output means 27 are provided. The operation amount / controlled variable correspondence table 26, the lever operation signals S ₁ of the work machine levers 9a, flow control quantity S ₂ is stored in correspondence. Therefore, the flow control amount S according to the inclination direction and the inclination angle of the work implement lever 9a
₂ is extracted by the control amount extraction means 25 and output to the electromagnetic proportional control valve 11 by the control amount output means 27. Furthermore,
The controller 10 includes a deceleration control amount calculating unit 28, a load /
The apparatus includes a deceleration control amount correspondence table 29, a determination unit 30, a slow speed control amount extraction unit 31, a load / slow speed control correspondence table 32, and a storage unit 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 association with each other. The larger the value, the smaller the deceleration control amount. The deceleration control amount is a temporal change of the flow rate control amount for obtaining the required deceleration, and has a smaller value as the load of the load is larger as shown in FIG. The larger the load,
This is because the deceleration is reduced to stabilize the load and eliminate impact. Note that the deceleration control amount is a positive value. The deceleration control amount calculating means 28 includes a load / deceleration control amount correspondence table 29
And outputs to the determining means 30 the extracted deceleration control quantity by subtracting repeatedly from the flow control quantity S ₂ of the present time from. For example, which the current flow control quantity S ₂ corresponding to 500 mm / sec, as long as the deceleration control amount is equivalent to 50mm / sec, 450mm / sec, 400mm / sec, the 350 mm / sec · · · The corresponding calculated values are output in order.

The load / slow speed control correspondence table 32 is a table that stores 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 slow speed control amount in association with each other. Slow speed control amount extraction means 31
Outputs the control amount of the slow speed extracted from the load / slow speed control correspondence table 32 to the determination means 30. The slow speed control amount is a flow rate control amount required to reach the slow speed,
The slow speed is a descending speed that is low enough to allow the load loaded on the fork to land without impact. In general, it is desirable that the fine velocity be smaller as the load is larger, as shown in FIG. This is because the greater the load, the more likely it is that impact will occur unless the load is lowered at a low speed. Judgment means 30
Is calculated by the deceleration control amount calculation means 28 (current flow control amount S ₂ -deceleration control amount) and the slow speed control amount extraction means 3
The control amount is compared with the very low speed control amount input from 1 and the larger one is selectively output 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 controlled variable correspondence table 29 from the flow control quantity S ₂ of the present time is greater than the crawling speed control amount, and outputs the calculated value (current flow control When the amount S ₂ -the deceleration control amount) is equal to or less than the slow speed control amount, the slow speed control amount is output.

The control amount output means 27 is a control amount extraction means 2
Either the flow control amount S ₂ input from the control unit 6 or the (current flow control amount S ₂ -deceleration control amount) to the slow speed control amount input from the determination unit 30 is selectively electromagnetically controlled by a detection signal from the position sensor 24. Output to the proportional control valve 11. That is, the work machine cylinder 1 is provided with a position sensor 24, which detects a constant lift immediately before the fork lands. As the constant lift, for example,
It is about cm. Until the position sensor 24 detects a certain lift immediately before the landing of the fork, the control amount output means 27 outputs the flow control amount S ₂ from the control amount extraction means 26 to the electromagnetic proportional control valve 11. Position sensor 24
When it is turned ON upon detecting that the pressure is below the predetermined lift, the control circuit 11 outputs the (current flow control amount S ₂ -deceleration control amount) to the very low speed control amount from the determination circuit 30 to the electromagnetic proportional control valve 11. Hereinafter, the control based on the slow speed control amount or the deceleration control amount will be referred to as soft touch control.
Incidentally, regardless of whether the detected position sensor 24 constantly may be provided with a mode switch to preferentially output the flow control quantity S ₂ from the control amount extraction unit 26.

In this embodiment having the above configuration, the forklift is specifically controlled according to a flowchart shown in FIG. First, after initialization, it is determined whether or not the work implement lever is neutral. When the work equipment lever is neutral,
Neutral control for maintaining the fork at a constant height is performed, and when the work implement lever is not neutral and is tilted, lift raising control for raising the fork or lift lowering control for lowering the fork is performed. In the case of the lift lowering control, when the position sensor 17 is turned on and it is detected that the 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 equal to or less than a certain value, the deceleration control amount is read from the load / deceleration control amount correspondence table 29 by the deceleration control amount calculating means 28 and the slow speed control is performed. The amount extracting means 31 reads out the slow speed control amount from the load / slow speed control table 32. At the same time, a mode set indicating soft touch control is performed. Since both the deceleration control amount and the slow speed control amount correspond to the load of the luggage, when controlled by soft touch control, as shown in FIG. Become. However, in the case of the deceleration control, the change of the gradient is large, but in the case of the slow speed control, the change of the gradient is small.

[0013] Thereafter, to confirm that it is the mode a set of soft touch, the extracted deceleration amount by subtracting repeatedly from the flow control quantity S ₂ of the previous value, the current flow rate control amount so calculated value Output as The calculated value is output to the electromagnetic proportional control valve 11 until the calculated value becomes equal to the slow control amount. For this reason, the lowering speed of the fork gradually decreases, resulting in a curve as shown in FIG. Then, the descending speed is equal to the slow speed, that is, the speed is reduced to such an extent that the load can be landed without impact. As described above, when (current flow control amount S ₂ -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 instead of the above value. For this reason, as shown in FIG. 8, the fork then descends at a constant speed, allowing the load to safely land without impact.

As described above, in the above embodiment, the descent speed of the fork can be automatically reduced to a very low speed at which the landing can be performed without impact, and the deceleration is adjusted according to the load of the load. Never give. Further, since the vehicle slowly decelerates to a very low speed rather than suddenly decelerate or stop, the load on the fork does not lose its balance and there is no danger of falling. Further, since no operator operation is required, the labor is reduced. In the above embodiment, the minute speed is changed according to the load of the load, but may be constant regardless of the load as long as no impact can be made. Instead of setting the fine speed, the speed may be reduced until the descending speed becomes zero. In particular, in the case of fragile luggage, it is necessary to suppress not only shock but also vibration at the time of landing, in which case it is better to suspend the descent once and then resume the descent slowly. It becomes safe control.

[0015]

As described above in detail with reference to the embodiment, the present invention performs a deceleration control for gradually decelerating automatically when the fork descends and falls below a certain height, and furthermore, the The deceleration is adjusted according to the load of the load. Therefore, even heavy luggage can be landed without impact, which is safe. Further, at a certain height, the descending speed can be increased, so that the working efficiency is improved. Further, since the operator does not need to operate the work implement lever at all, the labor is reduced. In addition, if the vehicle is decelerated to a fine speed at which landing can be performed without impact and then slowed down without further deceleration, the landing can be performed efficiently and without impact.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a flowchart showing the steps of one 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 an overall configuration of a forklift control device according to one embodiment of the present invention.

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

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

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

FIG. 8 is a graph showing fork lowering control.

[Explanation of symbols]

DESCRIPTION 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 Hydraulic sensor 24 Position sensor 25 Control amount extraction means 26 Operation amount / control 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 S ₁ lever operation signal S ₂ flow rate control signal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Midorikawa 3000 Tana, Sagamihara-shi, Kanagawa M.H.A. Showa 60-107405 (JP, U) Actually open Hei 2-139900 (JP, U) Actually open Showa 63-173197 (JP, U) Actually open Showa 60-183796 (JP, U)

Claims (2)

(57) [Claims] 1. A controller for outputting a flow control signal corresponding to a lever operation signal from a working machine lever to an electromagnetic proportional control valve, and supplying and discharging hydraulic oil to the working machine cylinder according to the flow control signal from the controller. In a forklift equipped with an electromagnetic proportional control valve and a working machine cylinder that expands and lowers a fork by expanding and contracting with pressure oil from the electromagnetic proportional control valve, a position sensor for detecting that the height of the fork has fallen below a certain level. A hydraulic sensor for detecting the load of the load loaded on the fork from the hydraulic pressure of the hydraulic oil supplied to and discharged from the working machine cylinder; and a positive deceleration control that decreases as the load detected by the hydraulic sensor increases. A load / deceleration control amount conversion table to be converted into an amount and a deceleration control amount converted by the table are repeatedly subtracted from the flow control signal and output. A deceleration control amount calculating means, and a control amount for, when the fork is detected by the position sensor, outputting a calculated value calculated by the deceleration control amount calculating means as a flow control signal to gradually reduce the descending speed of the fork. A control device for a forklift, comprising output means. 2. A controller for outputting a flow control signal corresponding to a lever operation signal from a working machine lever to an electromagnetic proportional control valve, and supplying and discharging pressure oil corresponding to the flow control signal from the controller to a working machine cylinder. In a forklift equipped with an electromagnetic proportional control valve and a working machine cylinder that expands and lowers a fork by expanding and contracting with pressure oil from the electromagnetic proportional control valve, a position sensor for detecting that the height of the fork has fallen below a certain level. A hydraulic sensor for detecting the load of the load loaded on the fork from the hydraulic pressure of the hydraulic oil supplied to and discharged from the working machine cylinder; and a positive deceleration control that decreases as the load detected by the hydraulic sensor increases. A load / deceleration control amount conversion table to be converted into an amount, and a deceleration control amount converted by the table asymptotically subtracted from the flow control signal and output. Deceleration control amount calculation means; slow speed control amount output means for outputting a slow speed control amount capable of landing a load loaded on the fork without impact; and the deceleration control amount when the fork is detected by the position sensor. The descending speed of the fork is gradually reduced by outputting the calculated value calculated by the calculating means as a flow rate control signal, and when the calculated value becomes equal to the slow speed control amount, the slow speed control amount is used as a flow control signal. And a control amount output means for outputting the fork and moving the fork at a very low speed.