JP2508401B2 - Forklift cargo handling protection device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cargo handling protection device for a forklift truck, which has a shock preventing function when the cargo bed is raised.

(Prior Art) Conventionally, as a hydraulic drive unit for driving a hydraulic actuator such as a lift cylinder or a tilt cylinder of a forklift, a pilot-operated type in which control valve switching operation is performed by pilot hydraulic pressure has been disclosed, for example, in Japanese Utility Model Laid-Open No. It is disclosed in the publication.

This is because the controller creates a pulse signal with a variable duty ratio corresponding to the lever tilt angle of the cargo handling lever, and this pulse signal is used to raise and lower the pilot hydraulic control pilot line provided in the pilot line of the pilot operated control valve. It drives an electromagnetic on-off valve. FIG. 4 shows the relationship between the lever tilt angle of the cargo handling lever and the average drive current of the solenoid opening / closing valve. The opening degree of the ascending / descending electromagnetic on-off valve corresponds to the duty ratio of the pulse signal. The spool of the control valve moves according to the opening degree of the ascending / descending electromagnetic on-off valve, and the amount of hydraulic oil supplied from the control valve to the lift cylinder or the amount of hydraulic oil discharged from the lift cylinder is adjusted.

The forklift disclosed in Japanese Patent Laid-Open No. 57-170398 has a lift detecting section for detecting the lift of the fork, and in the automatic lift operation for lifting the fork to a predetermined target height based on the detected lift signal. , It has a control function to gradually reduce the fork rising speed by pushing the switch.

(Problems to be Solved by the Invention) In a conventional forklift, the operation lever is operated because it is not easy to accurately see the lift during the work at a high place in the vicinity of the rising end of the loading platform or the operator makes an operation error. In such a state, that is, in a state in which a pulse current having a predetermined duty ratio is applied to the ascending electromagnetic on-off valve, the cargo bed may reach its ascending end at high speed.

In such a case, a big shock occurs, and there is a possibility that the load collapses, which is not preferable in terms of work.

In a forklift that gradually reduces the fork rising speed by pushing the switch as described above, it is possible to perform a slow stop at an arbitrary target lift, but in this case, it is necessary to push the switch one by one, which is troublesome. Further, even if the switch is pushed to decelerate in the vicinity of the target height, when the weight of the load is large, there is a problem that the ascending inertia before deceleration is large and the gear shift shock acting on the mast or the like is large.

The present invention has been made in view of the above problems, in which a collision shock does not occur at the rising end when the loading platform is raised, and
It is an issue to be solved to provide a cargo handling protection device for a forklift truck that has a small shift shock due to load variation.

(Means for Solving Problems) A cargo handling protection device for a forklift according to the present invention includes a hydraulic drive unit that raises and lowers a loading platform along a mast, a lifting height detection unit that detects a lifting height of the loading platform, and a loading platform of the loading platform. A load detection unit that detects a loaded load and an elevating control unit that controls the hydraulic drive unit based on the lifting height and the loaded load are provided, and the elevating control unit controls the rising speed when the loaded load is large. A rise protection control unit that reduces the damping start lift and raises the damping start lift of the rising speed when the load is small, and almost eliminates the rising speed of the platform just before the rising end. Is characterized by.

(Operation) The ascent protection control unit controls the hydraulic drive unit when the platform is lifted to attenuate the platform rising speed from a predetermined damping start lift.
Then, it disappears near the rising end.

The ascent protection control unit controls, based on the loaded load detected by the load detection unit, to lower the lift at the damping start point in inverse proportion to the loaded load.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIG.

The forklift to which this embodiment is applied has a lift cylinder 1 driven by a pilot operated control valve 2. The lift cylinder 1 is a chain (not shown), which is a bracket 30 and a fork 40 as a cargo bed in the present invention. Move up and down along. A pressure sensor 60 for detecting the hydraulic pressure (lift pressure) supplied to the lift cylinder is provided at the end of the lift cylinder, and this pressure sensor 60 constitutes the load detection section in the present invention. A chain wheel 80 for supporting the chain is provided at the upper end of the mast 50.

Further, in order to detect the rotation angle of the chain wheel 80, a lift sensor (a lift detecting section in the present invention) 90 composed of a rotary encoder is connected to the shaft of the chain wheel 80, while the driver seat Along with the operating lever 17, a soft stop switch 20 for instructing a gentle arrival at the rising end of the loading platform is provided.

The pilot operated control valve 2 is a motor M
A hydraulic drive unit according to the present invention is configured with the other hydraulic equipment shown in FIG. 1 including the driving hydraulic pump 3.

 The hydraulic drive unit will be described below.

The pressure oil discharged from the hydraulic pump 3 is divided into a main pipe 6 on the control valve 2 side and a PS pipe 7 for power steering by a flow dividing valve 5 provided in the discharge pipe 4. An oil chamber 8 for pilot operation is formed on one side of the control valve 2, and a pilot piston 9 is slidably fitted in the oil chamber 8 and the pilot piston 9 is connected to a spool 10 of the control valve 2. It is connected. The spool 10 is always held in the neutral position by the spring 11.

In this embodiment, the hydraulic pressure for the PS (4 kg / cm ^{2 at} all times)
Is used as the pilot pressure for spool operation.
That is, the pilot pressure is introduced into the oil chamber 8 so as to act on both sides of the pilot piston 9 through the pilot introduction conduit 12 connected to the PS conduit 7, and in the middle of this pilot introduction conduit 12. Is provided with a pressure reducing valve 13 for protecting the downstream portion and stabilizing the pilot pressure, and a solenoid valve for raising and lowering (a lifting control unit and a raising valve in the present invention are provided on the downstream side of the branch point. Part of the protection control unit) 14a, 14b are provided. The pilot pressure oil in the oil chamber 8 is led to the tank or the return pipe by the pilot drain pipes 15 connected to both sides of the oil chamber 8 with the pilot piston 9 interposed therebetween. Each of the pipe lines 15 is provided with a throttle valve (orifice) 16 that regulates a discharge flow rate.

That is, the control valve 2 introduces the pilot pressure oil into the oil chamber 8 through the pilot introduction pipe line 12 by the opening operation of the ascending or descending electromagnetic on-off valves 14a and 14b, while the pilot pressure in the oil chamber 8 is increased. The amount of pilot pressure acting on the pilot piston 9 is controlled by flowing out the oil at a flow rate limited by the throttle valve 16 of the pilot drain pipe line 15, and the pilot pressure and the force of the spring 11 are balanced. The spool 10 is adapted to be displaced. Therefore, by changing the current value applied to the solenoid on-off valves 14a, 14b and controlling the opening thereof,
The position of the spool 10 corresponding to that is obtained, and the lift cylinder 1 is supplied or discharged with an amount of pressure oil corresponding to the position of the spool 10. That is, the lift cylinder 1 moves up or down at a speed corresponding to the position of the spool 10.

The opening control of the electromagnetic on-off valves 14a, 14b is performed via a controller (the rest of the lifting control section and the lifting protection control section in the present invention) 19 based on the tilting operation of the operation lever 17 of the cargo handling operation section. The details will be described below with reference to FIG.

The controller 19 is connected to a cargo handling operation lever 17 (specifically, a potentiometer that interlocks with the lever) that outputs a voltage signal corresponding to the operation inclination angle, and the signal output from the operation lever 17 is a microcomputer with a built-in A / D converter. Device 19
Is input to Further, the signals (a, b) output from the pressure sensor 60 and the elevation sensor 90 are also input to the microcomputer device 19.

The microcomputer device 19 calculates the duty ratio of the current for driving the electromagnetic on-off valves 14a and 14b by performing arithmetic processing on each of the input signals, and supplies a pulse voltage having this duty ratio to a built-in constant current driver circuit (not shown). ) Via solenoid valve 14
Apply to a and 14b.

The operation will be described below with reference to the control flowchart shown in FIG.

First, initialization is performed (S10), and then it is checked whether the soft stop switch 20 is turned on (S11),
Wait until it is turned on. The soft stop switch 20 is a switch for canceling the soft stop mode according to the present embodiment when it is desired to keep the platform rising speed constant during high-altitude work. After that, the lever tilt angle, pressure, and lift are read from the operating lever 17, the pressure sensor 60, and the lift sensor 90 (S12, S14, S16), and normal lift control is performed based on the read memory tilt angle based on the map stored in the memory. Calculate the average drive current value at (S1
8).

Next, a new average drive current value is calculated using the soft stop average drive current characteristic map (see FIG. 3) stored in the memory (S22).

Next, the electromagnetic on-off valve 14a is driven by using one of the calculated average drive current value for normal lifting control or the average drive current value for soft stop, and the process returns to S12.

Hereinafter, this soft stop average drive current characteristic map (see FIG. 3) will be described.

In Fig. 3, the relationship between the lift and the average drive current at a load of 0, 0.5, 1.0, and 1.5t is shown by the characteristic lines C0 to C3. Actually, the above relationship is a map every 0.1t. Is memorized.

As shown in Fig. 3, the damping of the average drive current starts from the lift H1 at 1.5t, and the same applies below at 1.0t from the lift H2.
Attenuation starts from H3 at 0.5t and H4 at 0t. The average drive current is 0 immediately before the rising end.

Therefore, according to this embodiment, the heavier the load becomes, the lower the deceleration start height becomes, so that the deceleration acceleration acting at the start of deceleration becomes weaker and the deceleration shock decreases. Further, the average drive current becomes 0 immediately before the rising end, and a slight increase thereafter is covered by inertial energy.
There is almost no shock when reaching the rising end.

By the way, in FIG. 3, K1 is a deceleration mode with a duty ratio of 70% and a load of 0.5 t, and deceleration is performed from the lift H5 according to the characteristic line C1. Similarly, K2 has a duty ratio of 40.
%, It is the deceleration mode with a loading capacity of 1.5t, and deceleration is performed from the lift H6 according to the characteristic line C3.

Further, in order to further reduce the deceleration shock, the deceleration near the deceleration start time can be gently changed as shown by a curve M in FIG.

That is, the deceleration shock can be further reduced by decelerating while keeping the deceleration acceleration × (loading load + load weight) constant.

(Effects of the Invention) As described above, the cargo handling protection device for a forklift according to the present invention controls the hydraulic drive unit on the basis of the lifting height and the loading load of the loading platform to raise the loading platform rising speed near the rising end of the loading platform. It has a rise protection control unit that eliminates it and changes the decay start lift of the climb speed according to the load.

This reduces the collision shock when the loading platform reaches its rising end, and when the loading load is large, starts deceleration from an early stage to reduce the deceleration acceleration and reduce the deceleration acceleration and the loading load. The shift shock proportional to the product can be reduced.

Further, when the load is small, the shift shock is originally small, so that deceleration can be started with a relative delay, and the work time can be shortened by the rapid rise.

Therefore, according to the present invention, it is possible to reduce various shocks when raising a load and prevent unnecessary extension of working time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart showing its operation, FIG. 3 is an average drive current characteristic map diagram for soft stop, and FIG. 4 is a pilot drive of a conventional control valve. FIG. 5 is a characteristic diagram showing the relationship between the average drive current and the lever tilt angle in the electromagnetic on-off valve for vehicle, and FIG. 2 ... Control valve (hydraulic drive) 14a, 14b ... Electromagnetic on-off valve (hydraulic drive) 19 ... Microcomputer device (elevation control) (elevation protection control) 60 ... Pressure sensor (load detection) 90 ...... Lifting height sensor (lifting height detection part)

Claims (1)

(57) [Claims] 1. A hydraulic drive unit for raising and lowering a loading platform along a mast, a lifting height detecting unit for detecting a lifting height of the loading platform, a load detecting unit for detecting a loading load of the loading platform, the lifting height and loading. An elevating control unit that controls the hydraulic drive unit based on a load, wherein the elevating control unit reduces the damping start lift of the ascent rate when the loading load is large, and when the loading load is small. A cargo handling protection device for a forklift truck, comprising: a lift protection control unit that raises the damping start lifting height of the rising speed and substantially eliminates the rising speed of the platform just before the rising end.