JPS5930639B2 - Crane overload prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crane overload prevention system, in which a code corresponding to the working radius is generated from the boom length and the boom hoisting angle using an A-D conversion circuit, and the A standard rated voltage Vs corresponding to the rated load of the standard boom is generated from the output code of the D conversion circuit using a DA conversion circuit, and the difference in rated load (rated voltage) due to the difference in boom length at the same working radius is corrected. The purpose of this invention is to reduce the number of circuit components and increase accuracy by calculating the VSβ and the VS to generate a rated load (rated voltage) for each boom other than the reference boom.

The present invention will be described below based on drawings showing an example of implementation.

In FIG. 1, reference numeral 1 denotes a boom length determining circuit consisting of a boom length detection device, a boom length setting switch, etc., which generates a signal corresponding to the boom length.

The output of the boom length determining circuit 1 is set to a voltage VLa (1≦α≦m, where m is the number of boom stages) corresponding to the boom length LL.
It is input to a boom length voltage generation circuit 2 that generates a boom length voltage generation circuit 2 and a correction voltage generation circuit 3 that generates a correction voltage Vsβ (1≦β≦m−1) corresponding to the boom length.

The boom length voltage generation circuit 2 generates a voltage VLα corresponding to the boom length LL (1≦L≦m) from the output of the boom length determination circuit 1, and the output of the boom length voltage generation circuit 2 is This becomes one input of the working radius voltage generating circuit 5.

The working radius voltage generating circuit 5 inputs the output VLα of the boom length voltage generating circuit 2 and the output of the boom angle meter 4 that detects the boom angle θ, and from these two inputs, the working radius R = LL cos θ is obtained. Working radius voltage VR=Vt
, αcosθ are generated.

The output of the working radius voltage generation circuit 5 becomes the input of an A-D converter circuit 6, and the A-D converter circuit 6 outputs the working radius voltage V.
Let R be n types of digital quantities 81. (1≦L≦n).

The output of the A-D conversion circuit 6 is a working state setting switch 10 that determines working states other than boom length and boom angle.
It becomes the input of the code conversion circuit 7 together with the output of the .

The code conversion circuit 7 generates a code suitable for the working condition from the output of the A/D converting circuit 6 and the output of the working condition setting switch 10, and inputs the code to the DA converting circuit 8.

The DA conversion circuit 8 generates a rated voltage VS corresponding to the rated load of the reference boom from the output of the code conversion circuit 7.

The rated voltage Vs is the load detected when the rated load LL is applied to the boom of the crane with a reference length La (however, La can be arbitrarily selected) in the working state set by the working state setting switch 10. The voltage is the same as the output voltage of the device 11.

The output of the D-A conversion circuit 8 is supplied to the correction voltage generation circuit 3.
Together with the output, it becomes an input to the arithmetic circuit 9, and the arithmetic circuit 9 calculates Vs-V (1=Vo).

Output V of the arithmetic circuit 9.

enters the arithmetic processing circuit 12 together with the output VX of the load detection device 11, and calculates 〉:Vx /V c yb,
The calculation results are displayed on the display circuit 13.

The display method is, for example, when VX/Vo<0.9, the blue lamp is 0.
When 9≦Vx/Vc<1, yellow lamp and intermittent alarm sound, V
When X/vcn1, a red lamp and alarm sound will be emitted.

Next, to determine vLα, vs, and vsl, consider a crane with ratings as shown in the following table, for example.

Therefore, the load detection device 11 detects the lifting load and outputs a voltage corresponding to the load.

When the current reference boom length is Ll, the voltage corresponding to Ll is VL, then the voltage corresponding to boom length L2 is VL2 - T〒vL1, the voltage corresponding to boom length L3 VL3uVL3-toVL,, boom length L
The voltage vL4 corresponding to 4 is VL4=D÷VL・and 4・
Next is the standard 6 rated voltage R.

(-vTp) (1≦p≦n) is VT1=KX20.7
, v'r2=KX 17.5, VT3=KX 15.3
, VT4-KX13.4, VT,-KX 10.9, V
Let T6=KX9.1.

However, K is a proportionality constant. Also, the correction voltage VSβ is similar to the rated voltage Vs (=VTp), the correction voltage vs1 for boom length L2 is vsl- × 0.1, and the correction voltage vs2 for boom length L3 is Vs2-KXo, 2, boom length The correction voltage vs3 for the length L4=KX0.3.

In other words, as shown in the previous table, the difference due to the rated boom length is the same for each working radius if the working radius is the same, and the feature of the present invention is to utilize this regularity. .

For example, if the working radii are the same, the difference in rated load between boom L1 and boom L2 is 0.0 for all working radii.
1 ton, and 0.0 ton for boom L1 and boom L3.
0.3t On for 2ton boom L1 and boom L4
It is.

The second graph is a graph of the rated characteristics in the previous table converted to voltage.
It is a diagram.

The part A surrounded by a dashed-dotted line in Figure 2 does not appear in the actual rated characteristics (because the boom length is short), but it was set to take advantage of the regularity for all boom lengths. .

For example, in a working radius of 18 m, there is no rating for the boom length Ll, but by setting it to 7.0 tons, it can accommodate the entire boom length.

Next, the effects of the present invention will be described.

Generally, the maximum rated load of a crane is determined by the working radius.

Therefore, by distinguishing the voltage corresponding to the working radius and converting it into a digital quantity and recording it, it is possible to read out the rated voltage corresponding to the rated load for the working radius.

The rated voltage read from the code that encodes the working radius is the output voltage of the load detection device when the rated load is applied to the crane with the coded working radius, so it cannot be used with any type of load detection device. Furthermore, since the accuracy can be increased by reducing the voltage difference to be discriminated, it is possible to cope with sudden changes in the rated characteristics (output characteristics of the load detection device at rated load) with respect to the working radius.

Also, the rated load of a crane differs when the boom length is different and even if the boom hoisting angle is the same, but if the working radius is the same, the rated load is often the same or regular.

This regularity can be exploited by detecting and coding the working radius, and by using this regularity, the number of components in the circuit can be reduced and reliability can therefore be improved.

Regularity at the same working radius means that in the rated load table shown in the previous article, the rated load difference due to the difference in boom length is a constant value over all working radii (for example, Ll, R2, and 0) when compared at the same working radius. .1ton)tonashi,
This is called regularity.

Note that this regularity is observed only for the working radius.

In particular, even when no regularity is observed, it is possible to detect the boom hoisting angle by discriminating the voltage proportional to the hoisting angle θ.
It is advantageous to have the power to convert and discriminate sθ.

That is, the rating of the crane is determined by the working radius based on the load, and discriminating cos θ is more accurate than discriminating θ, and back-end processing is also easier.

Next, comparing the present invention with the conventional polygonal line approximation method, if part of the rated characteristics of a crane is approximated by a polygonal line as shown in FIG. 4, the circuit will become as shown in FIG. 3.

In FIG. 3, OP is an operational amplifier, and Vθ is proportional to the boom lifting angle.

Now looking at the bending points X and Y in Fig. 4, the voltage Vx at the bending point R2
2+R23), the corner voltages VX and vY are related to each other and cannot be determined independently.

Also, looking at the slopes of straight line XY and straight line Y7, the slope of straight line XY is -R8l/R1,Vθ, and the slope of straight line YZ is -Ro/R1
, Vθ.

However, R6' cannot be determined independently since the lines XY and YZ are also related to each other.

In addition, in Fig. 3, R11, R12, R21, R22゜R
232, R31, R32 proportional to R8, R1-2Ro1.
Ro2 should be sufficiently large.

As described above, the circuit constants that determine the valley fold line and the bending point are related to each other, and when one polygon line is to be changed, the circuit constants of the other polygon lines must also be changed, making adjustment complicated.

Furthermore, since the circuit constants that determine each broken line are not independent, changes in resistance value due to temperature change, changes in bending points due to voltage change, etc. affect the accuracy and require precision.

In addition, the polygonal line approximation generally becomes more complicated because several polygonal lines as shown in FIG. 4 are combined.

Compared to the above-mentioned conventional polygonal line approximation method, the present invention sets the rating characteristics by distinguishing and coding the working radius, so it can be set for each working radius independently, and therefore adjustment is easy. Since it does not affect the set value of the rated characteristics, it is possible to improve accuracy without being affected by changes in the external environment such as changes in temperature or voltage.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a graph expressing the rated characteristics in terms of voltage based on the crane load rating table in the specification, and Fig. 3 is based on the conventional polygonal line approximation method. The circuit diagram, FIG. 4, is a graph of polygonal lines when the circuit of FIG. 3 is used. DESCRIPTION OF SYMBOLS 1... Boom length determination circuit, 2... Boom length voltage generation circuit, 3... Correction voltage generation circuit, 4... Boom angle meter, 5... Working radius voltage generation circuit, 6.・・A-
D conversion circuit, 7... code conversion circuit, 8... D-A
Conversion circuit, 9... Arithmetic circuit, 10... Working state setting switch, 11... Load detection device, 12... Arithmetic processing circuit, 13... Display circuit.

Claims (1)

[Claims] 1 The crane overload prevention device is equipped with an A-D conversion circuit that generates a digital code corresponding to the working radius from the boom length and boom hoisting angle, and the output code of the A-D conversion circuit is used to generate a digital code corresponding to the rated load of the reference boom. 1. A crane overload prevention device, comprising: a D-A converter circuit that generates a rated voltage; and an arithmetic circuit that calculates a voltage determined by the output voltage of the D-A converter circuit and the length of the boom.