JPH04246099A - Forklift controller - Google Patents

Abstract

PURPOSE:To provide a controller which prevents mis-operation completely in starting an engine, in an electrohydraulic forklift which operates loading/ unloading work. CONSTITUTION:A condition where an lever operating signal has been already inputted from a working machine lever in starting an engine is judged to be dangerous, so an output into an electromagnetic proportional valve is stopped to make a working machine cylinder inoperative. It is thus impossible to operate a working machine by cylinder carelessly in starting the engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a forklift that can perform electrohydraulic cargo handling operations, and is improved to particularly improve safety.

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 the 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 pressure oil supplied to and discharged from the working machine cylinder 104 is adjusted, and the speed of elevation thereof 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

However, in conventional forklifts, the hydraulic pump 101 is capable of generating hydraulic pressure at the same time as the engine starts, so safety measures at the time of engine starting have become a problem. That is, when starting the engine of the forklift, if the work equipment lever 106 has already been erroneously tilted down from the neutral position, the lever operation signal from the work equipment lever 106 or the controller 105
Since the controller 105 outputs the flow rate control signal to the electromagnetic proportional control valve 102, the hydraulic pump 10
1 supplies pressure oil to the work machine cylinder 104, causing the work machine cylinder 104 to expand and contract inadvertently. For this reason, depending on the location of the work equipment, there is a risk of a major accident. For example, if you are stacking items on a fork,
When the fork was tilted forward due to a malfunction of the working machine cylinder 104, an accident occurred in which the load fell. In addition, if the potentiometer inside the work equipment lever 106 is misaligned, the same lever operation signal will be output even if the work equipment lever 106 is in the neutral position, which would be the same as if the work equipment lever 106 had fallen down. The work equipment cylinder may move, which is dangerous. If the work equipment lever could be automatically returned to the neutral position using a button switch, the above malfunction could be prevented, but having to do such a return operation every time the machine is started would be complicated to handle. turn into.

The present invention has been made in view of the above-mentioned prior art, and it is an object of the present invention to provide a forklift control device that prevents malfunctions during engine startup and ensures safety.

[0006]

[Means for Solving the Problems] The 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 a flow rate control signal from the controller. In a forklift truck equipped with an electromagnetic proportional control valve that supplies and discharges pressure oil to and from a work machine cylinder according to a control signal, and one or more work machine cylinders that expand and contract with the pressure oil from the electromagnetic proportional control valve, engine starting is performed. The controller is provided with a safety circuit that determines that it is dangerous and stops the output to the electromagnetic proportional control valve if a lever operation signal has already been input from the work equipment lever at this time. shall be.

[0007]

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 a control device for the forklift. As shown in the figure, the work machine levers 9a and 9b are formed of potentiometers.
A lever operation signal S1 whose current value is proportional to the amount of operation 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 to control the flow rate of the pressure oil flowing through the hydraulic line 16 to control the lift cylinder 1 and the tilt cylinder 8.
The operating speed of the work equipment levers 9a and 9b is controlled to correspond to the amount of operation of the work implement 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 an extracted main part of an embodiment of the present invention. As shown in the figure, the controller 10 of this embodiment includes a control amount extraction means 25, a manipulated variable control amount correspondence table 26, a control amount output means 27, and a safety circuit 24. The safety circuit 24 includes an output zero generating section 24
a and a signal selection section 24b. The zero output generating section 24a outputs a lever operation signal when the working machine lever is in the neutral position, that is, a zero output signal S0. The signal selection section 24b is connected to the starter switch 20,
If the lever operation signal S1 (a signal other than the neutral position) has already been input from the work equipment lever 9a when the engine is started by the starter switch 20, the output zero signal S0 from the output zero generator 24a is selected. The lever operation signal S1 from the work implement lever 9a is selected and output to the control amount extraction means 25 as it is except when the engine is started. Therefore, even if the work implement lever is already tilted down at the time of starting the engine, the control amount extracting means 25 receives the output zero signal S0, which is equivalent to the fact that the work implement lever 9a is in the neutral position. In other words, even if the work implement lever 9a is already tilted down from the neutral position at the time of starting the engine, the output of the flow rate control amount S2 from the controller 10 is stopped. Here, the engine starting time refers to, for example, the first several hundred milliseconds after the starter switch 20 is turned on. Therefore, if the lever operation signal S1 is inputted from the work equipment lever 9a after that, it will be assumed that the lever operation signal S1 has been operated after the engine has started.
It operates normally.

The operation amount/control amount correspondence table 26 stores the lever operation signal S1 of the work implement lever 9a and the corresponding flow rate control amount S2. 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. The electromagnetic proportional control valve 11 supplies and discharges pressure oil to and from the working machine cylinder 1 according to the flow rate control amount S2, thereby causing the working machine cylinder 1 to expand and contract. However, even if the work equipment lever 9a has already been pushed down from the neutral position when the engine is started, the work equipment cylinder 1 will not operate because the output zero signal S0, which is equal to the neutral position of the work equipment lever 9a, will be output. do not have. Therefore, it is possible to reliably prevent malfunctions in the case where the work implement lever 9a is tilted down from the neutral position before starting the engine, thereby ensuring safety. In addition, even if the potentiometer of the work equipment lever 9a is out of alignment and is in the neutral position, a lever operation signal may be output when the lever is pushed down from the neutral position. Even in such cases, this embodiment ensures that malfunctions will not occur. can be prevented. In the actual operation, it is preferable to automatically perform so-called zero point correction according to the flowchart shown in FIG.

That is, first, when starting the engine, an appropriate initial value is registered in the initial timer, and then the work implement lever 9 is
It is determined whether the lever operation signal from a is within an allowable range for the neutral position. That is, it is determined whether it is higher than the upper limit value of the neutral position and lower than the lower limit value of the neutral position. If the lever operation signal is within an acceptable range,
Since this is the displacement of the potentiometer, that value is set as the center of the neutral position and is used as the reference for subsequent lever operation signals. If it is within an unacceptable range, it is determined that the work implement lever 9a has been operated for some reason and has deviated from the neutral position. This process is repeated the number of times registered in the initial timer. The time when this is repeated is the engine starting point.

After the engine starting point has elapsed, it is determined whether or not the work equipment lever 9a has deviated from the neutral position at the engine starting time. If it has deviated from the neutral position, it is dangerous to operate the work equipment lever 9a. Regardless of the signal,
An output zero signal S0 is always output to the controller 10. Therefore, the output of the flow control signal S2 from the controller 10 to the electromagnetic flow control valve 11 is stopped. On the other hand, if the work machine lever 9a is not deviated from the neutral position at the time of starting the engine, it is safe and the work machine cylinder 1 is controlled as usual. That is, when the working machine lever 9a is tilted back and forth from the neutral position, the lift cylinder is controlled to rise or fall, and if it remains in the neutral position, the lift cylinder is controlled to maintain that position.

In this way, since the neutral position of the work machine lever 9a is determined when starting the engine, even if the work machine lever 9a is operated before starting the engine, the work machine cylinder 1 will not be accidentally moved. It is safe as there is no movement. Further, since the neutral position of the work implement lever 9a is corrected, there is an advantage that the accuracy of the control amount relative to the operation amount is increased.

[0016]

Effects of the Invention As described above in detail based on the embodiments, in the present invention, when a lever operation signal is already input from the work equipment lever at the time of starting the engine, the safety circuit operates. It is possible to prevent output to the electromagnetic proportional control valve. Therefore, at the time of starting, the working machine cylinder will not expand or contract inadvertently. Therefore, accidents at the time of starting can be prevented and safety can be improved.

[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.

[Explanation of symbols]

1 Lift cylinder 1a Piston rod 2 Outer mast 3 Inner mast 4 Fork 5 Bracket 10 Controller 11 Solenoid proportional control valve 14 Seat switch 16 Hydraulic pipeline 17 Oil pressure sensor 24 Safety circuit 24a　Output zero generation part 24b Signal selection section 25 Controlled amount extraction means 26 Manipulated amount/controlled amount correspondence table 27 Controlled amount output means S0 Output zero signal S1 Lever operation signal S2 Flow rate control signal

Claims (1)

[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 one or more work equipment cylinders that expand and contract with pressure oil from the electromagnetic proportional control valve, a lever operation signal is already input from the work equipment lever when starting the engine. A control device for a forklift truck, characterized in that the controller is provided with a safety circuit that determines that it is dangerous and stops the output to the electromagnetic proportional control valve when the electromagnetic proportional control valve is in danger.