JPS6343318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a highly accurate and easily adjustable overload prevention method for mobile cranes.
EMBODIMENT OF THE INVENTION Hereinafter, the structure and operation of the present invention will be explained in detail with reference to illustrated embodiments. FIG. 1 is a structural diagram of an embodiment in which a truck crane, which is a type of mobile crane, is equipped with a device according to the overload prevention method of the present invention. In the figure, 1 is the crane base, 2 is the base boom cylinder, 3 is the telescopic boom, 4 is the hook, 5 is the derrick cylinder, 6 is the boom length detector, 7 is the boom elevation angle detector, and 8 is the derrick cylinder pressure detection 9 is a microcomputer, 10 is an alarm indicator, 11
is an outrigger, and 12 is an elevation axis of the boom. That is, when using a crane, the telescopic boom 3 is extended from the base boom cylinder 2 according to the load position with the wheels of the truck lifted by the outrigger 11 at that position, and the booms 2 and 3 are extended by the operation of the derrick cylinder 5. The load is raised and lowered by moving up and down about the elevation axis 12. At that time, the boom length, boom elevation angle, and derrick cylinder pressure are measured by the boom length detector 6, boom elevation angle detector 7, and derrick cylinder pressure detector 8, respectively, and input into the computer 9 to calculate the load. If the load is compared with the limit load value and there is an overload, the alarm indicator 10
This will display a warning. FIG. 2 is a structural diagram of the boom depression/elevation angle detector 7 in FIG. 1. 21 in the diagram
The weight 22 is a resistor, 23 is a brush connected to the weight 21, and 24 is a rotation axis of the weight 21 and the brush 23. That is, since the resistor 23 is fixedly attached to the boom 2, the inclination of the resistor changes as the angle of elevation of the boom changes. On the other hand, since the weight 21 is always directly below, the brush 23
is always on a vertical line regardless of changes in the boom's elevation angle.

Therefore, since the contact position of the brush 23 with the resistor 22 changes according to the elevation angle of the boom, the boom elevation angle is detected by the output voltage. FIG. 3 is a structural diagram of the boom length detector 6 in FIG. 1. In the figure, 31 is a resistor;
32 is a brush, 33 is a gear box, 34 is a spring type cord reel, and 35 is a cord. That is, the tip of the cord 35 is fixed to the tip of the boom, and as the boom expands and contracts, the spring type load reel 34 rotates, which is decelerated by the gear in the gearbox 33, rotates the brush 32, and rotates the resistor 31.
The output voltage is changed by changing the contact position with the sensor.

FIG. 4 is an explanatory diagram showing the state of connection between the Derrick cylinder and the Derrick cylinder pressure detector. In the figure, 5 is the Derrick cylinder, 8 is the Derrick cylinder pressure detector, Pl is the rod pressure, and Ph is the head pressure. In other words, when the boom is stationary, no error will occur if the head pressure Ph is measured as the pressure due to gravity, but when the boom angle is changing, an error will occur if only the head pressure is measured, so it is necessary to measure the rod pressure Pl at the same time. However, Ph-αPl is made to be the pressure due to gravity. In the above equation, α is a constant representing the pressure receiving area ratio between the rod side and the head side of the Derrick cylinder. FIG. 5 is a diagram showing the internal structure of the Derrick cylinder pressure detector 8, in which A shows the structure of the pressure sensor, B shows the structure of the diaphragm, and C shows the circuit configuration of the cylinder pressure detector. In the figure, 50, 50a, 50b are pressure sensors, 51 is a diaphragm made of a metal plate that receives the hydraulic pressure from the Derrick cylinder, 53 is a moisture proofing agent, 54 is an input/output lead wire, 55 is a strain gauge (resistance strain gauge), 56a , 56b is an amplifier, 57 is a constant voltage power supply, 58 is an amplifier, 59
is a variable resistor for zero point adjustment. That is, as shown in FIG.
The output of the pressure sensor 50 changes in accordance with changes in the oil pressure, and the calculation of Ph-αPl is performed using the output of the pressure sensor 50b receiving the rod pressure Pl and the output of the pressure sensor 50a receiving the head pressure Ph, and the result is output. It was designed so that FIG. 6 is a block connection diagram showing an embodiment of the overload prevention method of the present invention.
In the figure, 61a to 61c are amplifiers, and 62 receives a selection command signal from a microcomputer 64.
A multiplexer connected to any of the output terminals 61a to 61c, 60a to 60z, and 60A according to a selection command, 63 an A/D converter that converts an analog signal from the multiplexer into a digital signal, 64 a microcomputer, and 65 a Microprocessor, 66 is input/output port, 67a
67c is a read-only memory, and 68 is a driver circuit for the alarm relay 69. Also, 60a-60
z, 60A is a coefficient setting device for calculating the hanging load, which is composed of a variable resistor. In the circuit configuration shown in Fig. 6, first, the boom lengths L ₁ , L ₂ , and
L ₃ (L ₁ < L ₂ < L ₃ ), boom angle 0 degrees, 10 degrees, 20 degrees,
... Measure the Derrick cylinder pressure at 80 degrees and store the value in the read-only memory 67a. When this measurement point is shown as a characteristic curve, it becomes a curve as shown in FIG.

Next are the limit loads at boom lengths L ₁ , L ₂ , L ₃ and boom angles of 0 degrees, 10 degrees, ... 80 degrees, that is, if a load exceeding these values is lifted, the crane itself will fall, or if it exceeds this value. Calculate the limit load at which the telescopic cylinder will buckle when the boom is extended with a load of
The value is stored in the read-only memory 67b of the microcomputer 64. FIG. 9 shows the relationship between this limit load and the boom angle as a characteristic curve. Furthermore, respectively, the boom length L ₁ ,
At L ₂ , L ₃ and boom angles of 0 degrees, 10 degrees, ..., 80 degrees, suspend a constant load W of known weight, measure the cylinder pressure F in that state, and calculate the hanging load by performing the following calculation. Calculate the coefficient K for

F ₂₀ = F - F ₁₀ K = W x L / F ₂₀ However, F ₁₀ is the cylinder pressure at no load, L is the boom length, F ₂₀ is the load component cylinder pressure, and each of these calculated coefficients Ka...
Kz and KA are coefficient setter 60a for calculating hanging load...
Set to 60z and 60A respectively. Figure 8 shows
It is a graph showing the relationship between this coefficient K, boom length, and boom angle. That is, the coefficient setter 60a...
The K values of points a...z and A in FIG. 8 are set in 60z and 60A, respectively. That is, set the K value of point a in Fig. 8 in the setting device 60a, the K value of point b in 60b, the K value of point c in 60c, and the K value of the corresponding point in all setting devices in the same manner. . Therefore, for example, even if only the K value at point b is changed to 60b, only the portions between points a and b and between points b and c of the curve in Fig. 8 will change, and the other portions will not change. Since it is not affected at all, only the vicinity of point b can be adjusted independently.
If the boom length is between L ₁ and L ₂ , the calculation will be based on the average value between the curves for L ₁ and L ₂ in FIG. 8. Cargo handling is started with the above preparations completed. Load W
When the is lifted, the boom length L, boom angle θ,
Cylinder pressure F is measured by boom length detector 6, boom angle detector 7, and cylinder pressure detector 8, respectively, and amplifiers 61a to 61c and multiplexer 6
2. Computer 6 via A/D converter 63
4. Then, in the computer, the cylinder pressure value at the time of boom length L and boom angle θ when there is no load is stored from the memory 67a to the microprocessor 65.
is read out, and proportional calculation is performed based on it to determine the cylinder pressure F ₁₀ at no load at boom length L and boom angle θ. At the same time, also
The boom length L is installed on the processor 65 in the computer.
The coefficient value for calculating the load near the boom angle θ is read from the coefficient setters 60a to 60z, 60A via the multiplexer 62 and A/D converter 63, and proportional calculation is performed based on it, and the boom length L, boom A load calculation coefficient K at the angle θ is determined. Furthermore, at the same time, the limit load value close to the boom length L and boom angle θ is determined by the microprocessor 6.
5, and proportional calculation is performed based on it to determine the boom length L and the limit load WL at boom angle θ. After that, the computer calculates F ₂₀ = F - F ₁₀ W = F ₂₀ × K/L, and the hanging load W becomes W>WL (however,
(K is an appropriate coefficient, usually about 0.9), the computer 64 sends the driver circuit 6
8, the alarm relay 69 is operated, and the alarm display 10 issues an alarm. As can be understood from the above explanation, in the present invention, we pay particular attention to the fact that the coefficient K when calculating the hanging load W changes from crane to crane, depending on the boom length, boom angle, aging, etc. are provided as variable resistors 60a to 60z, 60A, and the settings can be easily adjusted independently even in various boom postures, which has the excellent effect of making adjustment easy and enabling highly accurate overload detection. is brought about. In addition, in the above embodiment, the boom length
We have shown an example of measuring L ₁ , L ₂ , L ₃ and boom angles of 0 degrees, 10 degrees...80 degrees and storing them in memory, but of course this depends on the required accuracy. It goes without saying that it can be increased or decreased.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of an embodiment of a crane equipped with the overload prevention method of the present invention, Fig. 2 is a structural diagram of a boom depression/elevation angle detector, and Fig. 3 is a structural diagram of a boom length detector.
Fig. 4 is an explanatory diagram showing the combined state of the Derrick cylinder and the Derrick cylinder pressure detector, Fig. 5 is a structural diagram of the Derrick cylinder pressure detector, A is a structural diagram of the pressure sensor, B is a structural diagram of the diaphragm, and is a circuit configuration diagram of a cylinder pressure detector. Fig. 6 is a block connection diagram showing an embodiment of the overload prevention method of the present invention, Fig. 7 is a diagram showing the relationship between boom length and boom angle when no load is applied and cylinder pressure, and Fig. 8 is a diagram showing the relationship between boom length and boom angle - cylinder pressure. The relationship diagram of the suspension load calculation coefficient, FIG. 9, is a diagram of the relationship between boom length, boom angle and limit load.

Claims (1)

[Scope of Claims] 1. In a mobile crane with a variable boom length, a boom elevation cylinder pressure detector 8, a boom length detector 6, a boom elevation angle detector 7, a microcomputer 64, a setting device 60a for a suspension load calculation coefficient... 60
z, 60A, and the computer 64 stores in advance the cylinder pressure value at no load for an arbitrary number of representative boom angles and boom lengths, and the limit load for an arbitrary number of representative boom angles and boom lengths.
The suspension load calculation coefficient setter 60a stores the following suspension load calculation coefficients for an arbitrary number of representative boom angles and boom lengths in the internal memory.
...60z, 60A, and calculate the boom angle (θ) under load, the cylinder pressure value (F10) and limit load value (WL) at no load for the boom length (L), and the coefficient value for calculating the hanging load. (K) is calculated by the computer by proportional calculation based on the above-mentioned memorized value and the above-mentioned setting value, and the cylinder pressure (F) at the time of the load is measured by the cylinder pressure detector 8, and the above-mentioned computer calculates the formula F ₂₀ =F−F ₁₀ , W=
After calculating the hanging load value (W) using F ₂₀ × K/L, calculate the hanging load value (W) and the above limit load value (WL).
Compare with W>WL (where, is an appropriate coefficient)
An overload prevention method characterized in that an alarm is issued when.