JP2001163582A - Derrick cylinder pressure detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure detection device capable of accurately and stably detecting the pressure of the derrick cylinder of a crane over a wide range from low to high load. SOLUTION: Each of voltage values corresponding to each of detected pressure values is input to an actual load computing part through a respective input part (S31). The actual load computing part performs computation processes. In such processes, the input voltage is converted to pressure and the converted pressure from a detector is compared with a predetermined value, a correction value for the converted pressure indicated by the detection result selected in accordance with the comparison result is calculated and holding pressure P0 is calculated from the calculated value and converted to a corresponding voltage value (S32). The value is subjected to A/D conversion by an overload preventing device and the resulting digital value is compared with an allowable load value to detect any overload (S33). A warning or stopping process is performed in accordance with the comparison result (S34).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device, and more particularly to a pressure detecting device for detecting a derrick cylinder pressure of a crane.

[0002]

2. Description of the Related Art A crane working vehicle having a boom is provided with a derrick hydraulic cylinder, and the boom can be raised and lowered by increasing or decreasing the internal pressure. This derrick cylinder 8
As shown in FIG. 8, 0 (hereinafter simply referred to as “hydraulic cylinder”) is usually a detector P1 that converts the pressure (P1) on the cylinder head side into a corresponding voltage and detects it, and a pressure on the cylinder rod side. And a detector P2 which converts (P2) into a corresponding voltage and detects the voltage, and inputs each detection result to the overload prevention device 82. The overload prevention device 82 has an A /
After the input voltage value is converted into a digital voltage value by a D converter (not shown), a load moment (actual load) applied to the boom 81 is calculated based on the converted voltage value. If it is determined that the calculated value is close to the voltage value corresponding to the allowable load,
A warning instruction is issued to the alarm device 83 to alert the operator of the crane, or a stop instruction is issued to the stop device 84 to stop the boom up and down.

[0003] In general, crane work is in a wide range from a high load to a low load due to a variety of materials to be suspended, and the detection result of the detector P1 for detecting the pressure applied to the hydraulic cylinder in such a range is highly accurate. Is required. In recent years, with the rise of structures, hydraulic equipment,
For example, the need for using a hydraulic cylinder for raising and lowering a boom at a high load has increased, and the hydraulic cylinder has been used at a high pressure in conjunction with the technical improvement of hydraulic equipment. Therefore, the detection result of the detector P1 is required to have higher accuracy over a wider range.

In general, if one detector P1 is to detect a wide range of pressure from a high load to a low load, the accuracy depends on the resolution of the A / D converter itself. There is a problem that accuracy is reduced. For example, in the case of a resolution of 10 bits, the detection result is represented by 1024 (= 2 ¹⁰ ) data, so that the detection accuracy per bit becomes coarser in proportion to the range of the detection application range. . On the other hand, when the resolution is increased, the A / D converter is generally expensive, the cost is increased, and the adjustment thereof is complicated. Therefore, at present, it is not a preferable measure to improve the detection accuracy.

For example, when an accuracy of about 1 kg / cm ² (hereinafter simply referred to as “k” and 10 k ≒ 1 MPa) is required, a detector having a rated 350 k is required
Since 0k * 0.3% = 1.05k, the accuracy is 0.3
% FS (full scale). This is rated 50
At 0k, an accuracy of 0.2% FS is required. It is not so difficult to manufacture detectors with a rating of 400k and 500k, but in order to achieve high accuracy, it is necessary for the manufacturer to improve the manufacturing accuracy of each part and to make adjustments more precise. Due to the small size, adjustment is required before use.

Further, for example, a detector accuracy of 0.3
% (1/333), a resolution of 10 (1/333) is required in consideration of the accuracy of the A / D converter (for example, ± 0.25 bits).
Bit (1/1024 * 2.5 bits = 1/410) is possible, but at 0.2% (1/500), resolution of 10 bits is insufficient, and 11 bits (1/2048)
You need the above. However, A / D converters with high resolution are expensive and generally have slow conversion speeds. In addition, the performance cannot be exhibited unless peripheral circuits such as an analog reference power supply are also made highly accurate. Therefore, using a high-resolution A / D converter to improve detection accuracy is not a good measure.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems, and its object is to
An object of the present invention is to provide a pressure detecting device that can accurately detect a derrick cylinder pressure of a crane.

Here, it is possible to detect pressure due to low load using only a detector applicable to high pressure, but the pressure value per bit indicating the detection accuracy is large in a relatively low load range. This results in a coarse detection result. However, in general, the detection accuracy for high pressure and the detection accuracy for low pressure do not need to be the same, and the fact that sufficiently good detection results can be obtained with higher accuracy for low pressure than for low pressure,
That is, the pressure detection device of the present invention is based on the fact that it is not necessary to have uniform detection accuracy in all detection ranges.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned object, and its gist is to provide a device for detecting a pressure generated in a derrick cylinder for raising and lowering a crane boom. A plurality of detecting means for detecting a pressure value in the derrick cylinder; a selecting means for selecting any one of the detecting means based on the detection results of the plurality of detecting means; and a detecting means from the selected detecting means. And calculating means for calculating the pressure generated in the derrick cylinder, wherein each of the plurality of detecting means comprises:
Having a different detection range, the selection means, when the detection result from the selected detection means is out of the detection range,
The apparatus is characterized in that another detection means is selected to switch the detection result, and that the detection results before and after the switching time are corrected to match.

[0010]

The pressure detecting device of the present invention detects a plurality of pressure values in a derrick cylinder of a crane by a plurality of detecting means having different detection ranges, and based on the plurality of detection results, detects any one of the detection results. The pressure generated in the derrick cylinder is calculated based on the selection. If the selected detection result is out of the detection range, switch to the detection result from the other detection means, correct the detection results before and after the switching time to match, and derrick to raise and lower the crane boom. The pressure generated in the cylinder is detected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the pressure detecting device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing the vicinity of a derrick cylinder at the base of a boom including a pressure detector of the pressure detection device of the present invention, and FIG. 2 is a schematic diagram of an overload prevention device including the pressure detection device of FIG. FIG. 3 shows a block diagram, and FIG.
4 shows a schematic overall flow up to an alarm or a stop instruction based on a detection result. Here, the same components as those of the conventional device shown in FIG. The derrick cylinder 10 of FIG. 1 further includes a pressure detector P3 for detecting the pressure on the cylinder head side separately from the detectors P1 and P2, in addition to the detectors P1 and P2. Having a range. Each applicable detection range is a range in which a relatively low pressure can be accurately detected, for example, 0 to 35M.
Pa and a range in which a relatively high pressure can be accurately detected, for example, 0 to 50 MPa. Also, each detector P1,
P2 and P3 convert the detected pressure value (MPa) into a corresponding voltage value, and input each voltage value to the actual load calculation unit 20 through each of the input units p1, p2, and p3 (step S31 in FIG. 3). ). The actual load calculation unit 20 includes a CPU 20a that performs calculation processing (step S32), and a memory 20b in which the CPU 20a stores corresponding data for converting each input voltage value into a pressure value Pa and various calculated values. In the arithmetic processing in step S32, the input voltage is pressure-converted with reference to the memory 20b, and the converted pressure (P
A comparison is made as to whether 1) is within the detection range, a correction value of the converted pressure of the selected detection result is calculated according to the comparison result, a holding pressure (PO) is calculated from the calculated value, and a holding pressure (PO) is calculated.
Is converted to a corresponding voltage value. The converted value is input to the comparison unit 82a of the overload prevention device 82, where it is A / D converted, and the digital value is compared with the allowable load value from the allowable load input unit 21 to perform overload detection (step S33). According to the comparison result, the alarm or stop processing is performed in the same manner as described with reference to FIG. 8 (step S34).

FIG. 4 is a graph showing the relationship between the converted pressure value Pa of each detection result (voltage value) of the detectors P1 and P3 and the pressure PD generated by the derrick cylinder. FIG. 5 is a graph showing the relationship between the detected pressure shown in FIG. FIG. 3 shows the converted pressure Pa of the detection result of the detector P3.
7 is a graph showing the relationship between the reduced pressure Pa and the pressure PD generated on the cylinder head side when the calculation processing of FIG.
FIG. 6 shows a schematic flow of the calculation process (step S32) of FIG.

As shown in FIG. 4, the converted pressure Pa (solid line in FIG. 4) of the detection result of the detector P1, which is applicable to a low pressure load, is proportional when the generated pressure PD is equal to or lower than a constant pressure (rated pressure). When the pressure exceeds a certain pressure, the converted pressure Pa shows a constant value, and the detector P1 enters a non-detectable state. On the other hand, the converted pressure Pa (dotted line in FIG. 4) of the detection result of the detector P3 whose application range is up to a high load is proportional to the generated pressure PD up to the rated pressure of the detector P3. Here, a high-load detector P
3 and the detector P1 for low load, it is desirable that the converted pressures Pa of the detectors P1 and P3 coincide with each other at the generated pressure PD that is equal to or lower than the rated pressure. Currently do not match. In the example of FIG. 4, the converted pressure Pa of the detector P3 shows a smaller value. In this case, unless the converted pressure Pa of each of the detectors P1 and P3 matches the value of the corresponding generated pressure PD at the switching pressure Pc of the detector, the comparing unit 82 of the overload prevention device 82
This causes a problem in that the comparison result in “a” fluctuates and an accurate overload detection result cannot be obtained. For example, when the generated pressure is 35.0 MPa, each detector is set to 34.8 MPa.
a, 35.3 MPa in some cases, and the difference may cause a sudden change in the processing in the overload prevention device at the time of switching. Therefore, the detection result of the detector P3 is
The correction is performed as described below in accordance with the respective detection results of P1 and P2 (indicated by the dashed line in FIG. 5), and as shown by A in the graph of FIG. Are proportional to each other at a constant rate of change.
Here, the switching pressure Pc is, for example, a value that can be determined by the rated pressure on the detector side with a lower rated pressure.

FIG. 6 shows an operation flow (zero correction) for executing the operation process S32 of FIG. The pressure value is shown in parentheses, and the unit is MPa. First, the detection result from the detector P1 is converted into a corresponding pressure (P1) (step S61), and it is determined whether the pressure is 30 MPa or more (step S62).
It is determined whether the pressure exceeds 5 MPa (step S63). y
If es, it is determined from the detected pressure (P3) of the detector P3 according to the corrected pressure (P3X) = (P3) + (dP3) (step S64), and the holding pressure (PO) = (P3X) -K
* (P2) is obtained (step S65). Step S6
In No. 2, if no, the holding pressure (PO) = (P
1) -K * (P2) is obtained (step S67). If the answer is no in step S63, a correction value dP3 = (P1)-(P3) of the detected pressure (P3) is obtained (step S66), and then the above step S67 is performed.
After step S65 or S67, the holding pressure (PO) is converted into a corresponding voltage value (step S68), and the converted value P0 is input to the comparison unit 82a of the overload detection device 82. The comparing unit 82a A / D converts the converted value PO and compares the digital value with an allowable value to detect an overload. here,
K indicates a pressure receiving area ratio between the head side and the rod side of the derrick cylinder.

FIG. 7 shows an operation flow (span correction) for an operation process different from that of FIG. In this calculation process, the pressure (P1) corresponding to the detection result from the detector P1 is converted (step S71), and it is determined whether the pressure is 30 MPa or more (step S72). If yes, the pressure exceeds 35 MPa. It is determined (step S73).
If yes, it is determined from the detected pressure (P3) of the detector P3 according to the corrected pressure (P3X) = (P3) * (dP3) (step S74), and the holding pressure (PO) = (P3X) -K
* (P2) is obtained (step S75). Step S7
In No. 2, if no, the holding pressure (PO) =
(P1) −K * (P2) is obtained. Step S7
In No. 3, if no, a correction value dP3 = (P1) / (P3) of the detected pressure (P3) is obtained (step S76), and then the holding pressure (PO) = (P1) -K * (P2). Is obtained (step S77). Step S72 or S7
After 6, the above step S77 is performed. Step S7
5. After S77, the holding pressure (P0) is converted into a corresponding voltage value (step S78), and the converted value P0 is input to the comparison unit 82a of the overload detection device 82. The comparator 82a A / D converts the converted value P0 and compares the digital value with an allowable value to detect an overload.

As described above, the calculation flows of FIGS. 4 and 7 are different from each other in the correction value calculation formula and the correction formula. The correction value of the pressure (P3) in FIGS. 4 and 7 is, as described above, the equation (P3) + (dP3) and the equation (P3) × (dP3). The gradient is the same as P3), but the gradient is different in span correction.

Here, when the basic correction procedure is arranged,
For example, if the rated pressure of the detector P1 is 35 MPa,
The converted pressure (cylinder head side) is as follows: (1) When the pressure (P1) is 0 to 35 MPa, the detection result of the detector P1 is used. (2) When the pressure (P1) = 35 MPa, the pressure (P1)
3) correction value, (P3) + (dP3) or (P3) ×
(DP3) is used. (3) When the pressure (P1) exceeds 35 MPa, the calculation is performed by performing the above-mentioned correction (2) on the detection result of the detector P3.

Here, the work of taking in the pressure detection is performed at a certain timing (for example, 0.1 second).
Especially when the pressure change is steep, the pressure (P1) is 35MP.
When the value matches a, it may not be the capture timing. In this case, since the correction value cannot be calculated in time, the pressure (P1) is in a certain range, and in the examples of FIGS.
When the pressure is 0 to 35 MPa, a correction value of the pressure (P3) is calculated in advance and secured in the memory. This prevents a delay in the calculation of the holding pressure due to the correction, and thus a delay in the operation of the overload prevention device. If the pressure exceeds 35 MPa, a converted pressure is calculated from the pressure (P3) using the correction value.

Next, as a specific embodiment, the pressure generated during the operation of the derrick cylinder: 2 to 40 MPa or more P1: The maximum value of the pressure that can be detected by the detector 35MPa
a (allowable value of 52.5 MPa that does not damage the detector) P3: Rated pressure 50 MPa Accuracy of P1 and P3: 0.5% FS Assuming 0.5% FS, the maximum error at the generated pressure of 2 MPa is P
In the case of 1, it is 8.75% from the following formula. 35 × 0.005 = 0.175 Pa, 0.175 ÷ 2 =
0.0875.

In P3, it becomes 12.5% from the following formula. 50 × 0.005 = 0.25 Pa, 0.25 ÷ 2 = 0.
125.

The resolution is 10 bits (0 to 1024).
In the case of the A / D converter, P1 is about 0.03 MPa /
The bit P3 indicates a resolution per bit of about 0.05 MPa / bit. From this, in the pressure detecting device of the present invention, at the time of a low load of 35 MPa or less, which is the switching pressure, the derrick cylinder generated pressure is finely reduced to 0.03 MPa per bit by the existing A / D converter (resolution 10 bits). In addition to being detectable, it can be detected at 0.05 MPa per bit under a high load exceeding 35 MPa. Accordingly, when compared with a conventional pressure detecting device that detects a range from low load to high load with one detector, the pressure detecting device of the present invention maintains the same detection accuracy as the conventional device at high load while maintaining low detection accuracy. This is a more practical pressure detecting device capable of detecting the detection accuracy under a load at a finer accuracy than under a high load.

Further, since two detectors for detecting the pressure on the cylinder head side are provided and each detection is performed in parallel, it is possible to mutually detect a detector failure, and the detector for low load fails. Even if the same, the detector for high load can be used for the entire detection range.

[0024]

According to the pressure detecting device of the present invention, the derrick cylinder pressure of the crane can be detected accurately and stably over a wide range from a low load to a high load.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the vicinity of a derrick cylinder at the base of a boom, including a pressure detector of a pressure detection device of the present invention.

FIG. 2 is a schematic block diagram of an overload prevention device including the pressure detection device of FIG.

FIG. 3 shows a schematic overall flow from pressure detection to a warning or stop instruction based on the detection result.

FIG. 4 is a graph showing the relationship between the converted pressure value Pa of each detection result (voltage value) of the detectors P1 and P3 and the pressure PD generated by the derrick cylinder.

5 is a conversion pressure P of a detection result of the detector P3 shown in FIG.
converted pressure Pa when the arithmetic processing of FIG.
6 is a graph showing the relationship between the pressure PD generated on the cylinder head side.

FIG. 6 shows an operation flow (zero correction) for executing the operation process S32 of FIG. 3;

FIG. 7 shows an operation flow (span correction) for operation processing different from that of FIG.

FIG. 8 is a conceptual diagram showing the vicinity of a derrick cylinder at the base of a boom including a pressure detector of a conventional pressure detection device.

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[Procedure amendment]

[Submission date] January 7, 2000 (2000.1.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Here, when the basic correction procedure is arranged,
For example, if the rated pressure of the detector P1 is 35 MPa,
The converted pressure (cylinder head side) is as follows: (1) When the pressure (P1) is 0 to 35 MPa, the detection result of the detector P1 is used. (2) When the pressure (P1) = 35 MPa, the pressure (P1)
3) correction value, (P3) + (dP3) or (P3) ×
(DP3) is calculated in advance. (3) When the pressure (P1) exceeds 35 MPa, the detection result of the detector P3 is used after the correction of the above (2).

Claims (1)

[Claims] An apparatus for detecting a pressure generated in a derrick cylinder for raising and lowering a crane boom, a plurality of detection means for detecting a pressure value in the derrick cylinder, and a detection result of the plurality of detection means And a calculating means for calculating a pressure generated in the derrick cylinder based on a detection result from the selected detecting means. Each of the means has a different detection range, and when the detection result from the selected detection means is out of the detection range, the selection means selects another detection means and switches and switches the detection result. An apparatus for correcting detection results before and after a time point so as to match.