JPH0314754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crane boom support force detection device of the type that detects the pressure of an elevation cylinder of a telescopic boom.

The maximum allowable hanging load of a crane (hereinafter referred to as allowable lifting load) depends on the length of the boom, the angle of inclination of the boom,
There are restrictions on various conditions of use, such as the presence or absence of a jib and the presence or absence of outriggers, and if the load exceeds these limits, accidents such as the crane falling over and the boom breaking may occur. Various so-called moment limiter devices and overload detection methods for detecting such overloads of cranes have been proposed and put into practical use. In the moment limiter device mentioned above, there are two methods for measuring the crane's suspended load: a method that detects an amount directly proportional to the suspended load, such as the hoisting rope tension, and a method that detects the crane's boom supporting force. , the present invention relates to the latter method. The latter boom support force detection method is free from the influence of friction caused by the sheep, friction of the rope, and the like. There are no effects of fleet angle, reduced efficiency due to the load on the detection unit, or limitations due to the number of hoisting ropes (odd or even), and there is no need for a cable winding device or detectors for both the main hoist and jib systems. This method is superior to the former rope tension detection method in the following points.

However, to detect the boom support force,
When a method of detecting the pressure of the elevating cylinder for elevating the boom was adopted, the following problems occurred.

FIG. 1 is a schematic diagram showing a schematic configuration of a boom support force detection device in this type of moment limiter device.

In the figure, reference numeral 1 denotes an elevating cylinder, into which a piston 2 is slidably fitted, and a piston rod 3 is provided on one end surface side (upper surface side in the figure) of the piston 2. The end of the piston rod 3 and the extension of a telescopic boom (hereinafter referred to as boom) 4 are rotatably connected to each other by a pin 5. Here, the space in the elevating cylinder 1, with the piston 2 as a boundary, in which the piston rod 3 is located is defined as the rod-side cylinder chamber 1b, and the space on the opposite end surface side of the piston 2 is defined as the non-rod-side cylinder chamber 1a. One end of an oil feed pipe 6 is connected to the rod side cylinder chamber 1b, and one end of an oil feed pipe 7 is connected to the non-rod side cylinder chamber 1a. Each is connected to a hydraulic circuit 8 including valves, pressure regulating valves, and the like. 9 and 10 are oil feed pipes 7
and pressure detectors installed in the paths of 6 so as to communicate with each other.

In such a configuration, the hydraulic pressure in the elevation cylinder 1 is generally high pressure in the non-rod side cylinder chamber 1a.
The pressure is detected by a pressure detector 9 installed on the side of the oil feed pipe 7 which is communicated with. However, the hydraulic pressure in the non-rod side cylinder chamber 1a has hysteresis due to the configuration of the hydraulic circuit 8 including the elevation cylinder 1, as shown in the characteristic diagram marked with the symbol A in FIG. The detected value during the raising operation of the boom 4 [A-1 in Figure 2 A] and the detected value during the lowering operation [A-2 in Figure 2 A] indicate different hydraulic pressures at the same inclination angle of the boom 4. show. Therefore, if the output of the pressure detector 9 is used as is, for example, the safety device of the moment limiter device will be activated and the crane will stop operating even though the load is being lifted below the allowable lifting load. This causes an inconvenience.

In order to solve this problem, conventionally, in addition to the pressure detector 9, a pressure detector 10 has been installed on the oil feed pipe 6 side communicating with the rod side cylinder chamber 1b. That is, the rod side cylinder chamber 1b
The hydraulic pressure in the cylinder chamber 1a on the non-rod side has characteristics as shown in Fig. 2B, and has hysteresis characteristics for the same reason as described above for the hydraulic pressure in the non-rod side cylinder chamber 1a. B-1]
Also, during the lowering operation (B-2 in FIG. 2B), the hydraulic pressure is constant regardless of the change in the boom inclination angle. Focusing on this point,
Some systems have been designed to calculate the difference between the outputs of both pressure detectors 9 and 10 and equalize the hydraulic pressure at the same tilt angle of the boom during the crane's raising and lowering operations. However, this configuration requires two systems each of expensive pressure detectors, amplifiers, and various regulators, and also requires a difference calculator and regulator. As a result, the configuration becomes complicated, the device itself becomes quite expensive, and the costs (labor costs) increase as the two systems of pressure transducers, regulators, etc. must be configured and adjusted individually. It was a contributing factor.

The present invention has been made in view of the above circumstances, and its purpose is to have a simpler circuit configuration than conventional devices of this type, to reduce the number of parts and device adjustment man-hours, and to significantly reduce costs. Moreover, it is an object of the present invention to provide a boom supporting force detection device for a crane that can detect boom supporting force with high accuracy.

In order to achieve the above object, the present invention provides a boom support force detection device for a crane of the type that detects the pressure of an elevating cylinder of a telescopic boom, on the non-rod side of the elevating cylinder that adjusts the boom inclination angle of the crane. a pressure detector that detects internal cylinder pressure; and a rate of change calculating means that calculates a rate of change in the output of the pressure detector or the output of an angle detector that detects the inclination angle of the boom in the normal operating range of the crane; A discrimination means for discriminating whether the operating direction of the boom is in the upward direction or the downward direction based on the magnitude and polarity of the calculation output output from the change rate calculation means; a correction value setting means for generating an output corresponding to the difference between the detected pressures of the pressure detector during upward direction operation and downward direction operation; and a correction value setting means for adding the output of the correction value setting means to the output of the pressure detector. or a calculation circuit that reduces the boom support force, and the calculation circuit is configured to obtain an output corresponding to the boom supporting force in which hysteresis caused by the hydraulic circuit configuration including the cylinder is cancelled.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a circuit diagram showing the circuit configuration of an embodiment of the present invention, and FIGS. 4A to 4E show the output signals of each block of the circuit shown in FIG. FIG. The pressure detector according to the present invention is of a type that detects only the pressure in the non-rod side cylinder chamber 1a, and the pressure detector 10 shown in FIG. 1 is not used. The illustrated embodiment will be referred to as an embodiment of the present invention.

In FIG. 3, the output from a pressure detector 9 (shown in the first diagram) provided on the non-rod side cylinder 1a is inputted to a load amplifier 12 via an input terminal 11. The pressure detection signal amplified by the load amplifier 12, that is, the signal indicating the boom supporting force, is passed through a first low-pass filter 13 (0.3 Hz in this embodiment) consisting of a resistor R1 and a capacitor C1.
By cutting the above signals), unnecessary components caused by vibrations of the boom 4, etc. are removed. The signal output from the first low-pass filter 13 is applied to the positive input terminal of a difference circuit 14 as an arithmetic circuit. At this time, the input signal to the positive input terminal of the difference circuit 14 has the characteristics as shown in FIG. Show characteristics.

On the other hand, the output of the load amplifier 12 is passed through a changeover switch 15 to a second low-pass filter 16 (in this embodiment, cuts signals of 0.3 Hz or higher) composed of a resistor R2, a capacitor C2, and an operational amplifier A1. Also input. The signal from which unnecessary components have been removed by the second low-pass filter 16 is input to a differentiating circuit 17 comprised of a capacitor C3, a resistor R3, and an operational amplifier A2. This differentiation circuit 17 calculates the rate of change of the detected pressure, and outputs positive and negative signals for the positive slope and negative slope of the input signal, respectively. That is,
As shown in FIG. 4B, a negative signal (B-1 in the figure) is output when the boom is raised, and a positive signal (B-2 in the figure) is output when the boom is lowered. The output from this differentiating circuit 17 is the resistor R4, R5, R
6, is input to a comparator circuit 18 consisting of a diode D and an operational amplifier A3. Here, the resistor R6 is a chattering prevention resistor of the operational amplifier A3, and the diode D is a clamping diode that clamps the output of the operational amplifier A3 to zero when the output becomes negative. This comparator circuit 18 outputs a zero potential (C-1 in Figure 4C) when its input is negative, that is, when the boom is being raised, and when the input is positive, that is, when the boom is being lowered. The saturation potential [C-2 in Fig. 4C] is output.

In the circuit diagram of FIG. 3, only the processing circuit in the normal operating range is shown, and the processing circuit when the boom is stopped is omitted.

a variable resistor receiving the output of the comparison circuit 18;
A correction value setting device 19, which is a correction value setting means composed of a VR and an amplifier A4, generates a value V corresponding to hysteresis, that is, a signal corresponding to a hydraulic pressure difference for the same tilt angle during boom raising operation and boom lowering operation. . That is, this correction value setting device 19 outputs a voltage of "0" as shown in [D-1 in Fig. 4D] when the boom 4 is raised, and outputs a voltage of "0" when the boom 4 is lowered [D-1 in Fig. 4D]. D-2], a voltage signal of "V" is output, and these output signals are input to the negative input terminal of the difference circuit 14.

The signal input to the difference circuit 14 in this way is that when the boom is raised, the signal input to the positive input terminal is output as is to the output terminal 20, and when the boom is lowered, it is decreased by the value input to the negative input terminal. It is output to the output terminal 20. In other words,
From this difference circuit 14, as shown in FIG. 4E,
For the same boom inclination angle, the same pressure value, that is, the same boom supporting force is output during both the boom raising operation and the boom lowering operation.

In this way, according to the embodiment having the above configuration, hysteresis can be completely canceled by providing only one pressure detector 9 instead of two pressure detectors, so that the number of pressure detectors can be reduced. In addition to the bridge power supply that comes with the pressure detector, a high-precision (low-drift) preamplifier, a sensitivity adjuster,
Since equipment such as zero-point regulators can be reduced, the circuit configuration can be simplified and the cost of the device itself can be significantly reduced.In addition, the installation cost of pressure detectors can be reduced, and the cost during shipping and on-site work can be reduced. Labor costs are reduced by significantly reducing initial settings and various adjustment man-hours. Moreover, since the signal output from the difference circuit 14 always shows the same value for the same boom inclination angle, whether the boom is moving up or down, the The load values also correspond exactly to the actual hanging loads.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention.

For example, to determine the direction of boom movement,
The output of the pressure detector 9 is passed through the second low-pass filter 1.
6 to the differentiation circuit 17, and the rate of change is calculated and input to the comparison circuit 18, which is a discrimination means.As an input to the differentiation circuit 17, an angle detector ( For example, as shown in FIG.
1, amplifier 22, changeover switch 15, differentiation circuit 1
A similar result can be obtained by inputting the signal to the comparator circuit 18 via 7. Further, in the above embodiment, the differentiation circuit 17 is used as a change rate calculating means for calculating the change rate of the output of the pressure detector or the angle detector, but it is not necessarily limited to this. The calculation may be performed using a circuit or algorithm having a function equivalent to that of .

Furthermore, as a means for determining the upward and downward movement directions of the boom, a switch is provided to detect the positional relationship of the control lever that controls the raising of the boom or the members that interlock with it. It is also possible to provide a positive or negative signal to the comparison circuit 18.

Further, in the above embodiment, the detection output of the pressure detector 9 during the boom raising operation is outputted from the difference circuit 14 as is, and the detection output of the pressure detector 9 during the boom lowering operation is the corrected value. Although the configuration is such that the difference circuit 14 outputs a signal obtained by subtracting the value V corresponding to the hysteresis generated by the setting device 19, the following configuration is also possible.

That is, an adder circuit 14 is used in place of the difference circuit 14 in FIG. 3, and the output of the pressure detector 9 during the boom lowering operation is directly output from the adder circuit, and the output of the pressure detector 9 during the boom lowering operation is outputted from the adder circuit.
For the output of , the value corresponding to the hysteresis V
It may also be configured such that only 1 is output from the adder circuit. In this case, the value output from the adder circuit is
The value is higher than the value when the boom is raised by an amount corresponding to the hysteresis, but since this value is proportional to the boom supporting force, it may be adjusted as appropriate using a coefficient unit, adjuster, etc.

By the way, the present invention relates to a boom supporting force detecting device for a crane. Please refer to FIG. 5 to see how the boom supporting force detecting device of the present invention is applied to the above-mentioned moment limiter device. I will briefly explain.

FIG. 5 is a schematic diagram of a crane having a telescopic boom and raising and lowering the boom using an elevating cylinder. In the figure, l is the boom length, θ is the boom inclination angle, W is the suspended load, w is the horizontal distance from the boom foot pin P to the suspended load position, G is the boom's own weight, and g is the boom center of gravity from the boom foot pin P. The horizontal distance to the position, F is the elevating cylinder supporting force (hereinafter referred to as boom supporting force), and f is the vertical length from the boom foot pin to the extension line of the elevating cylinder. In the figure, equation (1) holds true from the moment balance conditions around the boom foot pin P.

F・f=G・g+W・w ...(1) From equation (1) F=(g/f)・G+(w/f)・W ...(2) From equation (2), the hanging load W on the crane If the boom supporting force when there is no W=0 is F ₀ , then
We obtain the following equation (3).

F ₀ =(g/f)・G (3) Also, the coefficient of the load term in equation (2) is set as δ, and the following equation is set.

δ=w/f (4) The physical meaning of δ is that it represents the change in the boom supporting force per unit suspended load, and it represents load sensitivity.

By substituting equations (3) and (4) into equation (2), the boom supporting force F
Alternatively, the hanging load W can be expressed as in equations (5) and (6).

F=F ₀ + δ・W ……(5) W=(F−F ₀ )/δ ……(6) Equation (6) is the boom supporting force F when lifting the suspended load W, and the boom support force F when no load is applied. It is shown that the suspension load W can be calculated from three quantities: the boom support force F ₀ and the boom support force δ per unit suspension load. The safety of the crane can be confirmed by comparing the known permissible hanging load Wr with respect to the boom length l, boom inclination angle θ, or working radius with the hanging load W derived from the above equation (6).

Specifically, the boom support force F ₀ at no load (W = 0) in equation (3) and the boom support force per unit suspended load δ in equation (4) are calculated theoretically or approximated at the crane design stage. , and store the F ₀ and δ at each boom length l, each boom inclination angle θ, or working radius in a storage device provided in the crane, under various usage conditions of the crane, The safety of the crane, that is, the overload state of the crane can be determined by comparing the suspension load W determined from these with the allowable suspension load Wr corresponding to the conditions of use.

In this way, the detected value of the boom supporting force directly affects the measurement accuracy of the suspended load and, ultimately, the reliability of the moment limiter device.

As detailed above, according to the present invention, the circuit configuration is simpler, the number of parts is reduced, and the equipment is reduced, compared to the conventional device which detects the pressure in the elevation cylinder that elevates the crane boom to detect the boom supporting force. It is possible to provide a boom support force detection device for a crane that requires fewer adjustment steps, can therefore significantly reduce total cost, and can detect boom support force with high accuracy.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the general configuration of the boom support force detection device, Fig. 2 is a characteristic diagram showing the relationship between the oil pressure in the rod side cylinder chamber and the non-rod side cylinder chamber in the elevating cylinder and the boom inclination angle. 3
The figure is a circuit diagram showing a circuit configuration of an embodiment of the present invention.
4A to 4E are characteristic diagrams showing the relationship between the output signal from each circuit block and the boom inclination angle in the embodiment shown in FIG. A moment limiter device that raises and lowers,
FIG. 2 is a schematic diagram showing an example of application of the present invention. 1... Elevation cylinder, 1a... Non-rod side cylinder chamber, 1b... Rod side cylinder chamber, 2... Piston, 3... Piston rod, 4... Boom,
6, 7... Oil feed pipe, 8... Hydraulic circuit, 9... Pressure detector, 13, 16... Low pass filter, 14
... difference circuit, 17 ... differentiation circuit, 18 ... comparison circuit, 19 ... correction value setter.

Claims (1)

[Claims] 1. A boom support force detection device for a crane of the type that detects pressure in an elevating cylinder of a telescopic boom, comprising: a pressure detector that detects the pressure inside the non-rod side cylinder of the elevating cylinder that adjusts the boom inclination angle of the crane; a rate of change calculation means for calculating a rate of change of the output of the pressure detector or the output of an angle detector for detecting the inclination angle of the boom in a normal operating range of the crane; and a calculation output output from the rate of change calculation means. a discriminating means for discriminating whether the operating direction of the boom is in the upward or downward direction based on the magnitude and polarity of the boom; correction value setting means for generating an output corresponding to the difference between the detected pressures of the pressure detectors;
and an arithmetic circuit that adds or subtracts the output of the correction value setting means to the output of the pressure detector, and the arithmetic circuit corresponds to the boom supporting force in which hysteresis caused by the hydraulic circuit configuration including the cylinder is canceled. 1. A crane boom support force detection device, characterized in that it is configured to obtain an output of: