JP2755839B2 - 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-handling operation by means of an electromagnetic hydraulic system, and more particularly to an improved control device for safe operation.

[0002]

2. Description of the Related Art Conventionally, as a control device for a forklift that can be operated by an electromagnetic hydraulic system, for example, the one shown in FIG. 6 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 lift cylinder for raising and lowering a fork (not shown) along a mast or a tilt cylinder for tilting the mast 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 mast is tilted or the like and the tilt angle of the work machine lever 106 is adjusted, the flow rate of the pressure oil to the work machine cylinder 104 is adjusted, and the elevating speed and the like can be freely controlled.

[0004]

In a cargo handling operation of a forklift, generally, a pallet on which a load is placed is used to lift and carry the load along with the pallet.
This pallet is a cargo handling platform having an upper surface on which a load is placed, and forms a slot into which a fork is inserted. Therefore, when the load is lifted by a forklift, the fork 4 is inserted in parallel into the pallet 29 on which the load 30 is placed as shown in FIG. 7, and then the outer mast 2 is moved backward by the tilt cylinder 8 as shown in FIG. After the tip of the fork 4 is lifted by tilting, the inner mast 3 and the fork 4 are further raised along the outer mast 2 by the lift cylinder 1 as shown in FIG. The inner mast 3 is slidably fitted to the outer mast 2, and the lift cylinder 1 is attached to the outer mast 2. A pulley 25 is attached to the upper end of the piston rod 1 a of the lift cylinder 1. One end of a chain 26 wound around the pulley 25 is connected to the fork 4, while the other end of the chain 26 is fixed to the outer mast 2. ,
The fork 4 is suspended via a chain 26. The outer mast 2 is supported to be tiltable, and is tilted forward or backward by a tilt cylinder 8.

Conversely, when the load 30 is to be lowered, the fork 4 is lowered by the lift cylinder 1 (in this state, the tip of the fork 4 is still lifted).
After the pallet 29 lands on the floor, the mast 2 is tilted forward by the tilt cylinder 8 to lower the tip of the fork 4 as shown in FIG. Here, when pulling out the fork 4 from the pallet 29, the fork 4 only needs to be in a floating state with respect to the pallet 29, but if the fork 4 and the pallet 29 are in contact, the pallet 29 is dragged with the fork 4. In addition to damage, the load 30 placed on the pallet 29 may collapse or fall. For this reason, when pulling out the fork 4 from the pallet 29, it is visually checked whether the fork 4 is horizontal and the fork 4 is not in contact with the pallet 29, and then the fork 4 is carefully pulled out. However, in the case of work at a high place, it is difficult to visually confirm the work, and even a veteran worker frequently causes problems such as breakage of the pallet 29 and dropping of the load 30 thereon. The present invention has been made in view of the above-described conventional technology, and improves work efficiency.
An object of the present invention is to provide a forklift control device capable of safely carrying out cargo handling work without damaging fragile objects.

[0006]

According to a first aspect of the present invention, there is provided a controller for outputting a flow rate control signal corresponding to a lever operation signal from a work implement lever to an electromagnetic proportional control valve, and a flow rate from the controller. An electromagnetic proportional control valve that supplies and discharges pressure oil according to a control signal to a lift cylinder and a tilt cylinder; a lift cylinder that moves a fork up and down along a mast using pressure oil from the electromagnetic proportional control valve; and the electromagnetic proportional control valve And a tilt cylinder for tilting the mast with pressure oil from a forklift, wherein a tilt sensor is attached to the mast and a hydraulic pressure sensor for detecting a hydraulic pressure supplied to the lift cylinder is provided. When it is detected that the mast is tilted forward or backward, the mast is vertically moved by the tilt cylinder. Means for outputting a flow control signal and flow control for raising and lowering the fork by the lift cylinder until the load is matched with the empty load when it is detected that the load detected by the oil pressure sensor does not match the empty load. A means for outputting a signal is provided in the controller.

[0007]

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 5 show one embodiment of the present invention. FIG. 4 is a perspective view illustrating an example of a forklift applied to the present embodiment. That is, the inner mast 3 is slidably fitted to the pair of left and right outer masts 2,
The inner mast 3 is formed with an elevating part including a bracket 5 and a fork 4. The lift cylinders 1 are respectively attached to the outer masts 2, and FIGS.
0, the piston rod 1a of the lift cylinder 1
A pulley 25 is attached to the upper end of the pulley. One end of a chain 26 is connected to the bracket 5 and the fork 4,
The chain 26 is a pulley 25 at the upper end of the piston rod 1a.
And the other end is fixed to the outer mast 2. That is, the bracket 5 and the fork 4 are suspended by the chain 26. Therefore,
The bracket 5 and the fork 4 can be raised and lowered with respect to the outer mast 2 via the chain 26 by extending and retracting the lift cylinder 1 by hydraulic pressure and moving the pulley 25 at the upper end of the piston rod 1a up and down.
The outer mast 2 is supported by the vehicle body 7 so as to be tiltable in the front-rear direction, and can be tilted forward or backward from the vertical direction by the tilt cylinder 8. Therefore, in the case of unloading, the tip of the fork 4 can be lowered by tilting the outer mast 2 forward. The workability of each is kept good and safety is ensured. Here, although not shown in FIG. 4, an inclination sensor 24 is attached to the outer mast 2. Therefore, the inclination sensor 24 can detect the forward inclination or the backward inclination of the outer mast 2.

The work 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. 5 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 rate control signal S ₂ to control the flow rate of the pressure oil flowing through the hydraulic line 16, thereby controlling the operating speed of the lift cylinder 1 and the tilt cylinder 8. The control is performed so as to correspond to the operation amounts of the working machine levers 9a and 9b.

A hydraulic pressure sensor 17 is arranged in a hydraulic line 16 for the lift cylinder 1 and sends out a hydraulic pressure signal S ₃ indicating the oil pressure in the hydraulic line 16. Controller 10
Calculating a load load acting on the lift cylinders 1 and tilt cylinders 8 processes the oil pressure signal S ₃ is. Further, when the starter switch 20 housed in the console box 19 together with the warning light 18 is turned on, the controller 10 operates by being supplied with power from the battery 21 and operates the safety switch 12 and the seat switch 1.
4 when the Walkaway not operate controls to the zero degree of opening of the electromagnetic proportional control valve 11 a current value of the flow rate control signal S ₂ as zero. In the drawing, reference numeral 22 denotes a hydraulic pump, and 23 denotes a hydraulic oil source. Also, the electromagnetic proportional control valve 11, the hydraulic line 1
6. Hydraulic components such as the hydraulic pressure sensor 17 are provided by the working machine lever 9a.
The number corresponding to the number of ９9e is provided. In this embodiment, since two working machine levers 9a and 9b for raising and lowering and tilting are provided to perform the raising and lowering and tilting operations, 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. That is, the controller 10 includes a CPU 120, a clock generator 121, a memory 122, an A / D converter 123, an interface 124, a solenoid valve driving circuit 125, a power supply circuit 126, a battery 50, and the like. Work machine lever 9a
After being converted into digital signals by the lever operation signal S _1, tilt signal S ₄ that is output from the hydraulic signal S ₃ and the inclination sensor 24 is output from the oil pressure sensor 17, A / D converter 123 output from, CPU 120 Sent to The closing signals of the empty load set switch 27 and the automatic switch 28 are transmitted to the CPU 12 via the interface 124.
Sent to 0. The empty load set switch 27 is a switch for recording the oil pressure in a state where the luggage 30 or the pallet 29 is not placed on the fork 4, that is, the oil pressure due to the own weight of the lifting unit by the fork 4 and the bracket 5 as an empty load. The automatic switch 28 is a switch for operating the lift cylinder 1 and the tilt cylinder 8 so that the fork 4 is not in contact with the pallet 29 when the fork 4 is pulled out from the pallet 29. Electromagnetic valve driving circuit 125 according to the result of the CPU120 is driven, the flow control signal S ₂ is output to the electromagnetic proportional control valve 11.

[0011] Here, when turning on the empty load set switch 27, stores the oil pressure signal S ₃ which is detected by the oil pressure sensor 17 at that time as a hydraulic signal in empty load. Therefore, in order to store the hydraulic signal due to the weight of the lifting unit as the hydraulic signal of the empty load, it is necessary to turn on the empty load set switch 27 while the pallet 29 is not in contact with the fork 4. Also, lift the automatic switch 28 is intended to be introduced during withdrawal of the fork 4 from landing pallet 29, when turned on this, operation of the tilt cylinder 8 based on the tilt signal S _4, based on the oil pressure signal S ₃ The operation of the cylinder 1 is executed continuously. The operation of the tilt cylinder 8 based on the tilt signal S ₄ means that when the tilt signal S _{4 is} detected by the tilt sensor 24 that the outer mast 2 is tilted forward or backward, hydraulic pressure is supplied to and discharged from the tilt cylinder 8. Thus, the outer mast 2 is made vertical. The operation of the lift cylinder 1 based on the hydraulic pressure signal S ₃ means the hydraulic pressure signal S ₃ detected by the hydraulic pressure sensor 17.
Is different from the hydraulic pressure signal stored in the idle load, the lift cylinder 1
To extend and retract the fork 4.

As described above, when the automatic switch 28 is turned on, the operation of the tilt cylinder 8 and the lift cylinder 1 causes the fork 4 to come out of contact with the pallet 29 on which the fork 4 has landed. The package 29 placed on the pallet 29 is not dropped.
Normally, when the tilt mast 8 is operated to make the outer mast 2 vertical, the fork 4 is parallel, and the pallet 29 that has landed and the fork 4 are considered to be in non-contact. However, even in this case, it cannot be denied that the fork 4 is in contact with the pallet 29 that has landed for some reason. It is sure that there is.

In this embodiment having the above configuration, the forklift is controlled in accordance with the flowcharts shown in FIGS. First, in the control of the tilt cylinder shown in FIG.
After the initialization, it is determined whether or not the tilt lever is neutral. When the tilt lever is not in the neutral position, control is performed to tilt forward or tilt backward, and an output value corresponding to the tilt of the lever is calculated and output, as in the related art.
When the tilt lever is neutral, the automatic switch 28 is ON.
When the automatic switch 28 is ON, it is determined whether the inclination sensor 24 detects the forward inclination or the backward inclination of the outer mast 2.
However, the vertical outer mast 2, assumed to have a constant width rather than vertical strict sense, when the slope signal S ₄ from the tilt sensor 24 is in the predetermined deadband, before傾又the rearward inclination regarded Not. When the inclination sensor 24 detects the forward inclination of the outer mast 2, the tilt cylinder 8 is expanded and contracted to control the outer mast 2 to incline backward, and conversely, the inclination sensor 24 detects the backward inclination of the outer mast 2. In this case, the tilt mast 8 is controlled to extend and contract to tilt the outer mast 2 forward. Tilt sensor 2
When the tilt signal S4 of ₄ is in a certain dead zone, the output value is set to 0, assuming that the outer mast 2 is vertical, that is, the fork 4 is horizontal. The output value is set to 0 even when the automatic switch 28 is OFF.

Next, as shown in FIG.
Control, the lift lever is neutral after initialization.
Determine whether or not. If the lift lever is not neutral,
The control for raising or lowering the lift is performed. Lift lever
In the case of neutral, whether or not the empty load set switch 27 is ON
It is determined and if it is ON, from the oil pressure sensor at that time
Hydraulic signal S_ThreeIs the hydraulic signal for the empty load.
To remember. Next, determine whether the automatic switch is ON
If the automatic switch 28 is ON, the hydraulic pressure
Current oil pressure signal S_ThreeAt empty load
It is determined whether or not it matches the hydraulic pressure signal. However, here
Oil pressure signal S at the time_ThreeMatches the hydraulic signal at idle load
Whether to do so is not a strict agreement, but a certain width
In the range of + α and -α with respect to the empty load
If there is, it is considered a match. Current oil pressure signal S_Three
Is lower than the hydraulic signal at idle load,
4 is in contact with the pallet 29 or the like,
The fork 4 is raised by extending the lift cylinder.
Conversely, the current hydraulic signal S_ThreeIs the hydraulic signal in the empty load
If it is higher, the upper surface of the fork 4 is
When the lift cylinder is reduced.
Lower the fork 4. Current oil pressure signal S _ThreeIs empty
If the fork 4 is coincident with the hydraulic signal for heavy
The output value is set to 0 because it is not in contact with the pallet 29 etc.
You. Also, when the automatic switch 28 is OFF, the output
The value is set to 0.

As described above, in this embodiment, the automatic switch 2
When the switch 8 is turned on, the fork 4 is first adjusted horizontally as shown in FIG. 2 and then adjusted so that the fork 4 is not in contact as shown in FIG. Therefore, when the fork 4 is subsequently pulled out from the pallet 29, the fork 4 does not damage the pallet 29 and the load 30 on the pallet 29 does not fall. In particular, in the case of work at a high place, it is necessary to place the luggage 30 on the pallet 29 at a high place and pull out the fork. Conventionally, it was visually observed whether the fork was horizontal or not. However, in the present embodiment, it can be easily executed only by turning on the automatic switch 28.

[0016]

As described above in detail with reference to the embodiment, when the control device of the present invention pulls out the fork from the pallet, the lift cylinder and the tilt cylinder are extended and retracted to disengage the fork from the pallet. Since the adjustment is made so as to be in a contact state, it is possible to prevent the pallet from being damaged and to prevent the load on the pallet from falling. In particular, it is effective in a state where it cannot be visually confirmed such as work at a high place.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a control device of a forklift according to one embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control process of a tilt cylinder according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a control process of the lift cylinder according to the embodiment of the present invention.

FIG. 4 is an external perspective view of a forklift to which the present invention is applied.

FIG. 5 is a block diagram showing an overall configuration of a forklift control device according to an embodiment of the present invention.

FIG. 6 is a block diagram showing a conventional forklift control device.

FIG. 7 is an explanatory view showing how a fork is horizontally inserted into a pallet.

FIG. 8 is an explanatory view showing a state in which the tip of a fork inserted into a pallet is lifted by a tilt cylinder.

FIG. 9 is an explanatory view showing a state in which a fork is inserted into a pallet and lifted by a lift cylinder.

FIG. 10 is an explanatory diagram showing a state in which the tip of a fork inserted into a pallet is lowered by a tilt cylinder.

[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 18 Warning light 19 Console box 20 Starter switch 21 Battery 22 Hydraulic pump 23 Hydraulic oil source 24 tilt sensor 25 pulley 26 chain 27 empty load set switch 28 automatically switches 29 the pallet 50 battery 51 disconnection display unit 120 CPU 121 clock generator 122 memory 123 A / D converter 124 interface 125 solenoid valve driving unit 126 power supply circuits S ₁ lever operation signal S ₂ Flow control signal S ₃ Oil pressure signal S ₄ Tilt signal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshiyuki Midorikawa 3000 Tana, Sagamihara-shi, Kanagawa M.H.I-Sagami High-Tech Co., Ltd. (56) References JP-A-62-280200 (JP, A) Sho-59-82298 (JP, A) Sho-sho 60-107405 (JP, U) Sho-sho 57-165697 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B66F 9 / twenty four

Claims (1)

(57) [Claims] 1. 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 supplying hydraulic oil corresponding to a flow control signal from the controller to a lift cylinder and a tilt cylinder. An electromagnetic proportional control valve to be discharged, and a lift cylinder that raises and lowers the fork along the mast with pressure oil from the electromagnetic proportional control valve,
A forklift including a tilt cylinder for tilting the mast with pressure oil from the electromagnetic proportional control valve, wherein a tilt sensor is attached to the mast and a hydraulic pressure sensor for detecting a hydraulic pressure supplied to the lift cylinder is provided. When the sensor detects that the mast is tilted forward or backward, the tilt cylinder outputs a flow control signal that makes the mast vertical, and the load detected by the hydraulic pressure sensor matches the empty load. A controller for a forklift, wherein the controller is provided with means for outputting a flow control signal for raising and lowering the fork by the lift cylinder until the load is matched with an empty load when the absence of the forklift is detected.