JP2008019025A - Cargo handling control device for engine type forklift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase engine speed when operating a lift lever even in the case where a worker does not operate an accelerator pedal, and easily perform fine operation of lifting/lowering motion of a fork by a control lever when performing cargo handling work at high lift height. <P>SOLUTION: An engine type forklift is provided with a lever switch 6 for detecting whether or not the lift lever 5 is operated and a limit switch 10 for detecting the height of the fork. A controller 7 as a cargo handling control device is mounted to the engine type forklift. The controller 7 increases engine speed when the lift lever 5 is operated. When determining that an ON signal is input from the limit switch 10 and the fork lift height is high and that the lift lever 5 is operated, the controller 7 performs control to limit increase in the engine speed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cargo handling control device for an engine-type forklift.

  In general, in an engine-type forklift, the pump is driven by an engine, and the amount of hydraulic oil discharged from the pump is determined by the engine speed set by operating an accelerator pedal. Conventionally, as a hydraulic oil circuit device applied to such an engine-type forklift, even when the operator does not operate the accelerator pedal, the engine rotational speed is increased and hydraulic oil is supplied to the lift cylinder. An operation circuit device in a work machine for a forklift truck has been proposed (see Patent Document 1). The actuation circuit device described in Patent Literature 1 includes a limit switch that detects the operation of the lift lever, and a controller that controls the rotational speed of the engine. The controller includes a lift lever that causes the mast to move up and down the mast. Control is performed to increase the engine speed when an operation is detected. Therefore, in the operation circuit device described in Patent Document 1, the amount of hydraulic oil discharged from the pump can be increased even when the operator does not operate the accelerator pedal.

In addition, a control device for a reach-type cargo handling vehicle has been proposed in which a fine operation can be performed with a reach lever even when a cargo handling operation is performed at a high lift (see Patent Document 2). A control device for a reach type cargo handling vehicle described in Patent Document 2 includes a lift detector that detects a lift and an extension position detector that can detect that the reach lever has been operated and switched to the extension position. Prepare. Then, the control device for the reach type cargo handling vehicle detects that the movable mast has reached a predetermined height or more by means of the lift detector and that the reach lever has been switched to the extended position by the extension position detector. If detected, control is performed such that the rotational speed of the drive source for driving the pump is reduced. In other words, the control device for the reach type cargo handling vehicle suppresses the balance of the reach type cargo handling vehicle from being deteriorated by slowing the reach speed when carrying out the cargo handling operation at a high lift.
JP 2002-12398 A JP 58-140000 A

  In the operation circuit device described in Patent Document 1, when an operation for raising and lowering the mast with respect to the lift lever is performed, control is performed to increase the engine speed regardless of the lift height. Yes. Therefore, in the engine-type forklift to which the operation circuit device described in Patent Document 1 is applied, when the operation of the lift lever is detected by the limit switch, the control for increasing the engine speed even when working at a high lift is performed. Is carried out and the discharge amount of the hydraulic oil is increased. Therefore, it is difficult to finely adjust the lift amount of the fork by finely operating the lift lever.

  Further, in the control device for reach type cargo handling vehicle described in Patent Document 2, when it is detected that the reach lever has been switched to the extended position at high elevation, the discharge amount of the pump is reduced in order to slow down the reach speed. Yes. However, Patent Document 2 does not disclose a configuration for controlling the rotational speed of the pump drive source based on the operation mode of the lift lever in the engine-type forklift.

  The present invention has been made in view of the above-described conventional problems, and even when the operator does not operate the accelerator pedal, when the lift lever is operated, the engine speed is increased and the high lift height is increased. An object of the present invention is to provide a cargo handling control device for an engine-type forklift capable of easily performing a fine operation of lifting and lowering a fork by operating a cargo handling operation lever.

  According to the first aspect of the present invention, a lift cylinder that operates when hydraulic oil is supplied and moves the mast up and down, an oil pump that sends hydraulic oil to the lift cylinder, and the oil pump are driven. An engine, an operation valve that adjusts the amount of hydraulic oil supplied from the oil pump to the lift cylinder based on the operation amount of the cargo handling lever, and an operation state detection that detects whether or not the cargo handling lever is operated And an engine-type forklift having a height detecting means for detecting lift, the engine speed is determined when it is determined that the cargo handling lever is operated based on a detection signal from the operation state detecting means. Engine speed control means for controlling the engine speed to increase the engine speed, and the engine speed control means When it is determined that the lift is high, based on the detection signal from the operation signal and the detection signal from the operation state detection means, and when it is determined that the cargo handling operation lever has been operated, the engine speed The gist is to limit the increase of the engine speed by the increase control.

Here, “restricting the increase in engine speed” means that the increase amount of the engine speed is reduced or the increase amount of the engine speed is set to zero.
According to this configuration, when it is determined that the lift is a low lift, and it is determined that the cargo handling lever is operated, the engine speed is controlled by the engine speed control means even if the accelerator pedal is not operated. By increasing the engine speed, the engine speed is increased to increase the amount of hydraulic oil discharged from the oil pump. Further, when it is determined that the lift is high and the cargo handling lever is operated, the engine speed is not increased, or the increase amount of the engine speed is reduced. The amount of hydraulic oil discharged from the oil pump is reduced. Therefore, when the amount of operation of the cargo handling lever is the same at high lift, the fork moves up and down slowly, and it is easy to finely adjust the height position of the fork by finely operating the cargo handling lever.

  According to the present invention, even when the operator does not operate the accelerator pedal, the engine speed is increased when the lift lever is operated, and when the cargo handling operation is performed at a high lift, the fork is operated by the cargo handling operation lever. It is possible to easily perform the fine operation of the up and down movement.

An embodiment embodying a cargo handling control device of the present invention will be described below with reference to FIG.
An engine 2 used as a drive source for driving the oil pump 1 is mounted on the forklift.

  The oil pump 1 discharges hydraulic oil when operated, and the discharge amount of the hydraulic oil increases when the engine speed increases, and decreases when the engine speed decreases. A control valve 3 as an operation valve is provided on the downstream side of the oil pump 1, and hydraulic oil discharged from the oil pump 1 is supplied to the lift cylinder 4 through the control valve 3.

  A spool (not shown) that is mechanically connected to the lift lever 5 is provided in the control valve 3, and the control valve 3 is a lift in which the flow rate of hydraulic oil discharged from the oil pump 1 is operated by an operator. It adjusts based on the operation amount of the lever 5, and supplies it downstream.

  The lift lever 5 is provided at the driver's seat of the forklift and is configured to move a spool (not shown) in the control valve 3 according to the operation of the lift lever 5. The lift lever 5 is provided with a lever switch 6 as an operation state detecting means for detecting whether or not the lift lever 5 is operated.

  The lever switch 6 is provided with a potentiometer, and the lever switch 6 is electrically connected to a controller 7 as a cargo handling control device, and outputs a voltage corresponding to the operation amount of the lift lever 5 to the controller 7.

  The lift cylinder 4 is operated by the hydraulic oil supplied from the control valve 3 so as to expand and contract. The lift cylinder 4 is connected to the mast 8 so that the mast 8 can be moved up and down by expanding and contracting.

  The mast 8 includes a fork 9, and the fork 9 is configured to be movable from 0 mm above the ground to 3000 mm above the ground as the mast 8 moves up and down. The mast 8 is provided with a limit switch 10 as a lift detection means, and the limit switch 10 is electrically connected to the controller 7.

The limit switch 10 is provided to output an ON signal when the lift of the fork is high (for example, 2200 mm or more).
An accelerator pedal 11 provided in the driver's seat of the forklift is provided with a pedal depression amount sensor 12 constituted by a potentiometer. The pedal depression amount sensor 12 is electrically connected to the controller 7.

  The controller 7 can increase the engine speed according to the depression amount of the accelerator pedal 11. When the ON signal is input from the limit switch 10, the controller 7 determines that the lift of the fork is high. When the ON signal is not input from the limit switch 10, the lift of the fork is low. Judge. Here, “high lift” means the lift of the fork in which it is difficult to finely adjust the lift at a high lifting speed. When it is determined that the lift lever 5 has been operated based on the voltage output from the lever switch 6, the controller 7 includes an engine speed control means that performs engine speed increase control for increasing the engine speed.

Next, the operation of the cargo handling control device configured as described above will be described.
First, a description will be given of a case where the fork 9 is raised by operating the lift lever 5 without operating the accelerator pedal 11 when performing a cargo handling operation at low lift.

  When raising the fork 9, the operator operates the lift lever 5 backward to supply hydraulic oil to the lift cylinder 4. At this time, the lever switch 6 converts the operation amount of the lift lever 5 into a voltage and outputs it to the controller 7. If the voltage value output from the lever switch 6 is equal to or greater than a certain threshold value, the controller 7 determines that the lift lever 5 has been handled. The constant threshold value is a value set to make the operation of the lift lever 5 play. When the lift lever 5 is operated, the lift of the fork is low, so the on signal is not output from the limit switch 10, and the controller 7 indicates that the lift of the fork is low. Judge. When the controller 7 determines that the lift of the fork is low and the lift lever 5 is operated, the controller 7 outputs an engine speed increase command to the engine 2 to set the engine speed in a predetermined idle state. The engine speed increase control is performed to increase the engine speed (for example, 1000 rpm). The “idle engine rotational speed” means the rotational speed of the engine 2 operating in a state where the accelerator pedal 11 is not depressed. When engine speed increase control is performed, the amount of hydraulic oil discharged from the oil pump 1 increases and the amount of hydraulic oil supplied to the control valve 3 also increases. If the amount of hydraulic oil supplied to the control valve 3 increases, the hydraulic fluid sent from the control valve 3 to the lift cylinder 4 with the same operation amount of the lift lever 5 also increases. Therefore, the raising / lowering speed of the mast 8 is increased, and the fork 9 can be quickly moved to the target height position by the raising / lowering movement of the mast 8.

Next, a description will be given of a case where the fork 9 is raised by operating the lift lever 5 without operating the accelerator pedal 11 when performing a cargo handling operation at high lift.
When raising the fork 9, the operator operates the lift lever 5 backward to supply hydraulic oil to the lift cylinder 4. At this time, a voltage equal to or higher than a certain threshold is output from the lever switch 6 and the lift of the fork is high, so that an ON signal is output from the limit switch 10. At this time, since the controller 7 determines that the lift of the fork is high and the lift lever 5 is operated, the controller 7 performs control to limit the increase in the engine speed. That is, the controller 7 performs control to keep the engine speed at the idling engine speed set in advance without outputting the engine speed increase command for increasing the engine speed to the engine 2. When the controller 7 performs control to limit the increase in engine speed, the amount of hydraulic oil discharged from the oil pump 1 does not increase, and the amount of hydraulic oil supplied to the control valve 3 does not increase. When the amount of hydraulic oil supplied to the control valve 3 does not increase, the amount of hydraulic oil supplied from the control valve 3 to the lift cylinder 4 does not increase, so the mast 8 moves slowly. Therefore, in the case where the cargo handling work is performed at a high lift, when the operator operates only the lift lever 5 without operating the accelerator pedal 11 and moves the mast 8 up and down, the movement of the mast 8 becomes slow. Therefore, the operator can easily finely adjust the height position of the fork 9 by finely operating the lift lever 5.

Next, a description will be given of a case where the fork 9 is raised by operating the lift lever 5 without operating the accelerator pedal 11 when performing a cargo handling operation from low to high height.
When raising the fork 9, the operator operates the lift lever 5 backward to supply hydraulic oil to the lift cylinder 4. At this time, a voltage equal to or higher than a certain threshold is output from the lever switch 6 and the lift of the fork is low, so that an ON signal is not output from the limit switch 10. At this time, since the controller 7 determines that the lift of the fork is low and the lift lever 5 has been operated, the engine rotational speed increase control is performed and the hydraulic oil supplied to the lift cylinder 4 is controlled. Increase the amount. In such a state, the mast 8 continues to rise, and when the lift of the fork reaches a high lift, the limit switch 10 is switched on and an on signal is output to the controller 7. The controller 7 It is judged that the lift has become high. If the controller 7 determines that the lift of the fork has become high, the controller 7 stops the output of the engine speed increase command and performs control to limit the increase of the engine speed. The movement of the fork 9 becomes slow when the lift of the fork reaches a high height, and the operator finely adjusts the height position of the fork 9 by fine operation of the lift lever 5, and moves the fork 9 to the target height. Move to position.

In this embodiment, the following effects can be obtained.
(1) The controller 7 as a cargo handling control device includes an engine speed control means for performing engine speed increase control for increasing the engine speed when it is determined that the lift lever 5 is operated. When the controller 7 determines that the fork lift is high when the ON signal is output from the limit switch 10 and the lift lever 5 is operated, the controller 7 increases the engine speed. Control to limit.

  Accordingly, since the fork 9 can be moved slowly when the lift of the fork is high, the operator can finely adjust the height position of the fork 9 by finely operating the lift lever 5. Can be easily done. In addition, when the lift of the fork is low, the fork 9 can be quickly moved to the target height position by increasing the engine speed and supplying the control valve 3 without running out of hydraulic oil. Can do.

  (2) As a control for limiting the increase in the engine speed, the controller 7 does not output an engine speed increase command for increasing the engine speed to the engine 2 but keeps the engine speed in the idle state set in advance. Take control. For this reason, the control for limiting the increase in the engine speed can be realized only by causing the controller 7 to perform the process of not outputting the engine speed increase command. Therefore, the processing load on the controller 7 can be reduced when the control for limiting the increase in the engine speed is performed.

The embodiment is not limited to the above, and may be embodied as follows, for example.
As the lever switch 6, a limit switch may be used instead of a potentiometer.

  ○ As a control to limit the increase in engine speed at high lift, instead of performing control not to output an engine speed increase command to the engine 2, control is performed to reduce the increase in engine speed. Also good. Even when such control is performed, the movement of the fork 9 is slow when the lift is high. Therefore, it is easy to finely adjust the height position of the fork 9 by finely operating the lift lever 5. it can.

  ○ The engine speed limit for high lift may be divided into multiple stages. For example, when the lift is detected by dividing it into three or more stages and the mast 8 is moved up and down at a high lift, control is performed to gradually reduce the engine speed increase as the lift of the fork increases. May be. In this case, for example, a plurality of limit switches 10 as lifting height detecting means are provided on the mast 8 so that the controller 7 can determine the magnitude of the lifting height of the fork step by step based on a signal output from each limit switch 10. You can do it.

  O Instead of the limit switch 10, the lift detection means may be constituted by a sensor that continuously detects the lift. For example, a reel-type lift sensor is used as a lift detection means for continuously detecting the lift of the fork. The reel type lift sensor includes a wire (not shown) having one end connected to the fork 9, a reel (not shown) around which the wire is wound, and a rotation detector (rotary encoder) for detecting the amount of rotation of the reel. Prepare. In this case, since the lift of the fork can be detected continuously, when the mast 8 is moved up and down at a high lift, the control for continuously decreasing the amount of increase in engine speed as the lift of the fork increases. To increase the engine speed.

  The control for limiting the increase in the engine speed by the engine speed increase control may be performed when the fork 9 is lowered. That is, even when the fork 9 is lowered, if the controller 7 determines that the lift of the fork is high and the lift lever 5 is operated, the controller 7 limits the increase in the engine speed by the engine speed increase control. Take control.

  The controller 7 does not need to determine whether the lift of the fork is high or low based on whether the lift of the fork is 2200 mm or more or less than 2200 mm. The controller 7 determines that the lift is high when it is difficult to finely adjust the lift at a fast ascending / descending speed. There is no particular limitation.

  ○ Even if the controller 7 is high and the lift lever 5 is operated, when the accelerator pedal 11 is operated, the controller 7 performs control to increase the engine speed. Also good. In this case, even if the controller 7 determines that the lift is high and the lift lever 5 is operated, the fork 9 can be quickly moved when the operator desires.

  ○ When carrying out cargo handling work from low to high lift, even if the mast 8 moves up and down and the lift reaches from low to high, the engine speed when the controller 7 is low The fork 9 may be moved by continuing the ascent control.

The block diagram of a cargo handling control apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oil pump, 2 ... Engine, 3 ... Control valve as operation valve, 4 ... Lift cylinder, 5 ... Lift lever as cargo handling operation lever, 6 ... Lever switch as operation state detection means, 7 ... As cargo handling control device Controller: 8 ... mast, 9 ... fork, 10 ... limit switch as lifting height detection means.

Claims (1)

Based on the amount of operation of the lift cylinder that operates when the hydraulic oil is supplied and moves the mast up and down, the oil pump that sends the hydraulic oil to the lift cylinder, the engine that drives the oil pump, and the cargo handling operation lever An operation valve for adjusting the amount of hydraulic oil supplied from the oil pump to the lift cylinder, operation state detection means for detecting whether or not the cargo handling operation lever is operated, and lift detection for detecting lift An engine-type forklift with means,
Engine speed control means for performing engine speed increase control for increasing the engine speed when it is determined that the cargo handling lever is operated based on a detection signal from the operation state detection means; The number control means determines that the lift is high based on a detection signal from the lift detection means and a detection signal from the operation state detection means, and the cargo handling lever is operated. A cargo handling control device for an engine-type forklift that restricts an increase in engine speed by the engine speed increase control when it is determined that the engine speed has increased.

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