JPS6359960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fork horizontal control method for an automatic cargo handling forklift truck that improves the accuracy of the fork stop position.

FIG. 1 is an overall overview diagram showing an example of a forklift truck. In the figure, reference numeral 1 denotes a pair of left and right masts that are mounted on the front of a forklift truck 2 so as to be tiltable by a certain amount. The mast 1 is composed of an outer mast 1a and an inner mast 1b which is raised and lowered along the outer mast 1a. Further, 3 is a fork moored to a lifting member 4 that is raised and lowered along the mast 1, and 3a is the tip of the fork's horizontal portion 3b. Reference numeral 6 denotes a lift cylinder, and its operation causes the elevating member 4 to move up and down via the chain 5. Reference numeral 7 denotes a tail cylinder, which is operated by a tail control valve controlled by a tail servo (not shown), for example, to tilt the mast 1 forward or backward. 8 is the front wheel,
9 is the rear wheel.

In a forklift truck having such a structure, the unloading height H is usually calculated based on a change in the chain 5 or a rotational displacement of the chain wheel 11, as shown in FIG. Therefore, it is good when the horizontal part 3b of the fork 3 is horizontal to the ground as shown in FIG.
If it is tilted as shown in the figure, the height H' of the fork claw tip 3a from the ground is the calculated unloading height H
It's completely different.

Furthermore, during automatic cargo handling, it is first necessary to ensure that the mast 1 is perpendicular to the ground, so a horizontal sensor is installed to detect the inclination angle of the mast 1, and the mast 1 is automatically verticalized. When it receives that signal, it stops automatic verticalization operation and enters automatic lifting operation. (In FIG. 5, the block moves from block 50 to block 52).

However, even if the mast 1 is perpendicular to the ground in an unloaded state, if the load 12 changes, for example, the deflection of the front wheel 8 or the distortion of the inner and outer masts when the inner mast 1b is raised, as shown in Fig. 4, may occur due to the load 12. bending due to backlash at the overlapping point F, as well as the deflection of the mast 1 itself and the deflection of the horizontal part 3b of the fork 3, and the height H' of the fork toe 3a from the ground and the unloading height H based on the calculated value. The problem was that it would shift.

Therefore, the present invention eliminates such conventional drawbacks and provides fork horizontal control of a forklift truck using a microcomputer to control the fork horizontal 3b to be horizontal to the vehicle body according to the load of the fork. The method is described below with reference to the drawings.

FIG. 6 is a block diagram showing the main parts of an embodiment of the fork horizontal control method for a forklift truck according to the present invention. According to the rotation of the cylinder 7, it is interlocked via the crank lever 20 as shown in FIG. 7, and a voltage corresponding to the mast angle (mast inclination angle) is sent to the comparison section 22. The configuration of the comparing section 22 is shown in FIG.

In FIG. 8, E ₁ is a positive power supply terminal, I ₁ is an input terminal, and the output voltage of the potentiometer 21 is supplied to this input terminal I ₁ . _R0 to _R8 are resistances,
VR ₁ to _{VR 4} are variable resistors, and CP ₁ to CP ₅ are comparators. In the comparator CP ₁ , a set voltage V ₁ corresponding to a mast inclination angle of 0° is applied to its negative input terminal, and when the voltage applied to the positive input terminal is equal to or higher than the set voltage V ₁ , the output A becomes “1”. becomes. In addition, in the comparator CP ₂ , a set voltage V ₂ corresponding to a mast backward tilt angle of 1° is applied to its negative input terminal, and when the voltage applied to the positive input terminal is equal to or higher than the set voltage V ₂ , the output B
becomes “1”. Furthermore, in the comparator CP ₃ , a set voltage V ₃ corresponding to a mast backward tilt angle of 3° is applied to its negative input terminal, and when the voltage applied to the positive input terminal is equal to or higher than the set voltage V ₃ , the output C is It becomes “1”. In addition, in the comparator CP ₄ , a set voltage V ₄ corresponding to a mast backward tilt angle of 4° is applied to its negative input terminal, and the voltage applied to its positive input terminal is equal to the set voltage.
When V _{is 4} or more, the output D becomes "1". Furthermore, in the comparator CP ₅ , a set voltage V ₅ corresponding to a mast backward tilt angle of 12° is applied to its negative input terminal.
When the voltage applied to the positive input terminal is equal to or higher than the set voltage _V5 , the output E becomes "1". Here, V ₁ <V ₂ <
V ₃ <V ₄ <V ₅ .

As shown in FIG. 7, a fixing member 10 is attached to the outer peripheral surface of the tail cylinder 7, and a crank lever 20 is movable by loosely fitting its shaft 20a into the elongated hole 10a of the fixing member 10. A potentiometer 21 connected to the crank lever 20, that is, linked to the rotation of the tail cylinder 7, and a comparison section 2.
The output of the horizontal sensor consisting of 2, ie, the comparison section 22
The relationship between the output and the mast inclination angle is shown in FIG.

Outputs A to E from the comparator 22 are supplied to the microcomputer 23. Further, the microcomputer 23 detects the oil pressure using the oil pressure detector of the lift cylinder 6 as the load sensor 24, and obtains this oil pressure signal as a step or an analog value. Then, the load sensor 24 determines whether there is a live load 12 on the fork 3 by detecting the oil pressure, and if there is a live load 12, it turns on the switch 25 to send an output of "1" to the microcomputer 23, and turns the switch 25 off. In this case, a “0” output is input to the microcomputer 23.

On the other hand, the microcomputer 23 has a predetermined value for the fork horizontal portion 3 with respect to the load applied to the fork 3.
Memorize the setting of the mast backward inclination angle (range) where b is horizontal to the vehicle body. here,
For example, when there is no load on the mast rear tilt angle of 0° to 1° as the no-load neutral range,
b is the mast backward inclination angle that is horizontal to the ground. In addition, when there is a predetermined load, the mast backward inclination angle of 3° to 4° is considered as the load neutral range, and when the mast backward inclination angle is within this range, the horizontal part 3b of the fork is set to be horizontal to the ground, based on actual measurements. This is what I did. Therefore, microcomputer 2
3 is shown in the flowchart of FIG. 10 so that the mast backward inclination angle is within a predetermined mast backward inclination angle (range) for a predetermined load, that is, the horizontal part 3b of the fork 3 is horizontal. This is to perform program control of mast verticalization operation. This mast verticalization operation of FIG. 10 according to the present invention is performed as an improvement of blocks 50 and 51 of FIG. Based on the signal, automatic lifting operation starts from block 52 in FIG. 5.

In the microcomputer 23, input A="1",
When B, C, D = “0”, no load neutral, and A,
The operation shown in FIG. 10 will be described with reference to FIG. 9 when settings are made and stored based on actual measurements for load neutral and predetermined loaded loads when B, C="1" and D="0".

In the microcomputer 23, the load is determined in block 31, and if there is no load (when switch 25 is off), block 32 is executed.
It is determined whether A is on (A is “1”) or not, and if A is off (“0”), the no-load neutral range (A = “1”, B to D = “ The block 33 is tilted backward so that the voltage is in the range of 0", and the block 32 again determines whether or not A has become on ("1"). If A is on ("1"), In the next block 34, it is determined whether input B is off (“0”) or not, and if input B is on (“1”), the mast aft angle exceeds the no-load neutral range and is too far aft. Therefore, perform the forward tilt operation of block 35, and then move the block 3 again.
In step 4, it is determined whether input B is off (“0”) or not. If B is off (“0”), it means that the no-load neutral range has been entered, and the fork horizontal part 3b is horizontal. , becomes the horizontal control stop (horizontal stop) of block 36.

In addition, in the microcomputer 23, when there is a load, a block 37 determines whether input C is on ("1") or not, and input C is off ("0").
If so, the vehicle has tilted too far forward and has not entered the load neutral range, so a rearward tilt operation is performed in block 38. Then, input C is turned on (“1”) in block 37.
If input C is on (“1”), it is determined in block 39 whether input D is off (“0”), and if D is on (“1”), then the Since the tilt is too high and the load neutral range is exceeded, block 40 performs forward tilt operation, and block 39 again determines whether or not D is off ("0").
If so, the load is in the neutral range, so the horizontal control stop (horizontal stop) of block 36 occurs.

In this case, the microcomputer 23 has 3
The blocks 1, 32, 34, 37, and 39 are judged, and based on this judgment, the blocks 33, 3
A forward tilt control signal a or a backward tilt control signal b is sent to the tail servo 26 to control the tail servo 26 in order to perform the corresponding operations of backward tilt and forward tilt in steps 5, 38, and 40. This tail servo 26
By this operation, the tail control valve 27 is controlled, the tail cylinder 7 is operated, and the mast 1 is controlled to tilt forward or backward. As the tilt cylinder 7 rotates as the tilt angle of the mast 1 is controlled, the shaft 20a moves within the elongated hole 10a of the fixing member 10 attached to the tail cylinder 7. Potentiometer 21 sends a voltage signal corresponding to the mast inclination angle to comparator 22 in FIG. Based on the outputs A to E of the comparator 22, the flow shown in FIG. 10 is executed in the microcomputer 23.

In this embodiment, the microcomputer 23 stores a preset mast backward tilt angle range in which the horizontal portion of the fork is parallel to the vehicle body with respect to the carrying load of the fork 3; however, the present invention is limited to this. The mast rearward tilt setting angle at which the horizontal part of the fork is parallel to the vehicle body without being distorted by the load of the load is determined as a function of the mast rearward tilt setting angle against the load. It goes without saying that the mast backward inclination angle may be stored in the computer and controlled so that the mast backward inclination angle becomes a preset mast backward inclination angle (mast backward inclination setting angle) according to the actual load. For example, in the case of FIG. 4, according to the present invention, the fork horizontal portion becomes horizontal at the point (position) of the mast backward inclination angle θ ₀ as shown in FIG. 11, and the mast verticalization operation is stopped. In this case, θ ₀ increases as the load of the live load 12 increases.

As described above, when the mast verticalization operation in which the horizontal part of the fork becomes horizontal is completed, the horizontal part of the fork becomes horizontal to the ground, and at this time the mast "vertical" signal (vertical signal of the horizontal part of the fork) is generated. Based on this, the forklift truck enters automatic lifting operation as shown in Figure 5. When this mast verticalization operation is completed, the movement of the chain that raises and lowers the fork by the operation of the lift cylinder is detected and calculated by the displacement of the chain wheel, and the result matches the actual ground height of the horizontal part of the fork. Accurate stopping position for mast verticalization operation can be obtained.

According to the present invention described above, even if bending occurs due to deflection of the front tire of the forklift truck, deflection of the mast itself, or play at the connection point with the inner and outer masts when the inner mast b is in the raised state, the fork claw tip can be Since the actual height above ground matches the calculated height calculated by detecting the movement of the chain, for example, by the displacement of the chain wheel, a highly accurate stopping position can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a side view of a forklift truck to which the present invention is applied, Figs. 2 and 3 are explanatory diagrams for explaining the drawbacks of conventional forklift trucks, and Fig. 4 is a conventional forklift with a multi-stage mast. 5 is a flowchart of automatic lifting operation of a forklift truck, and FIG. 6 is a diagram of a fork horizontal control method of a forklift truck equipped with a microcomputer according to the present invention. FIG. 7 is a perspective view of a main part showing an embodiment of a fork horizontal sensor in a forklift truck according to the present invention; FIG. 8 is an implementation of a comparison section of FIG. 6. A circuit diagram showing an example, FIG. 9 is a diagram showing the relationship between the horizontal sensor output and the mast inclination angle, FIG. 10 is a flowchart of mast verticalization operation based on the method of the present invention, and FIG. This is an explanatory diagram of fork horizontal control by applying the invention method, in which 1 is the mast, 3 is the fork, 3a is the fork toe, 3b is the fork horizontal part, 6 is the lift cylinder, and 7 is the tail. Cylinder, 12 is load, 2
1 is a potentiometer, 22 is a comparison section, 23 is a microcomputer, 24 is a load sensor, 25 is a switch, 26 is a tail servo, and 27 is a tail control valve.

Claims (1)

[Claims] 1. A control method for leveling a fork attached perpendicularly to a mast to a vehicle body before loading or unloading a load with a forklift truck that is automatically controlled in height, comprising: In addition to providing a load detection means for detecting a live load, the mast has a preset no-load backward inclination angle in which the horizontal part of the fork is horizontal to the main body when there is no live load on the fork, and when there is a live load on the fork. A preset backward inclination angle of the mast under load, at which the horizontal portion of the fork is horizontal to the main body, is stored in the microcomputer in response to the applied load, and the fork is adjusted based on the detection signal of the load detection means. A microcomputer determines whether or not there is a load, and when it is determined that there is no load, the mast back tilt angle is the same as the above-mentioned no-load mast rear tilt angle, and when it is determined that there is a load, the mast rear tilt angle is Controls the tail servo by outputting a mast forward or backward tilt signal so that the tilt angle becomes the set mast rearward tilt angle when loaded, and tilts the mast forward or backward so that the horizontal part of the fork becomes horizontal. A fork horizontal control method for a forklift truck, characterized by: