JPS627671Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boom moment response electric signal generating device for a working vehicle having a boom whose elevation is controlled by a hydraulic cylinder. This type of boom moment response electric signal generating device is used as an actual measurement signal generating device that is compared with a limit value in a safety device that monitors the limit working state of a working vehicle such as a crane. Up until now, boom moment response electric signal generators have consisted of a pressure transducer installed on the load-holding side oil chamber side of a hydraulic cylinder for boom elevation adjustment and converting the oil pressure in the oil chamber into an electric signal and outputting it. Alternatively, it consisted of a load cell installed at the tip of the piston rod of a hydraulic cylinder for boom elevation adjustment. However, although the former type has the advantage of simple construction and low cost, the value detected by the pressure transducer does not match the load actually acting on the hydraulic cylinder. In the case of the latter, although it has the advantage of high accuracy, it has the disadvantage that the value is greatly deviated when compared with the load actually acting on it. Since the load cell is interposed in the structure, the structure is complicated, and the processing is troublesome and costly.

The present invention focuses on the fact that the disadvantages of the former are largely due to the frictional forces generated between the cylinder and the piston and between the cylinder and the piston rod in connection with the up-and-down movement of the boom. It is an object of the present invention to provide a boom moment response electric signal generating device that can solve the above-mentioned disadvantages while taking advantage of the advantage of low cost, and can generate an electric signal that accurately responds to the boom moment.

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram of a crane having a boom whose elevation is controlled by a hydraulic cylinder, in which the present invention is implemented, and here a truck crane is shown. In Figure 1,
Reference numeral 1 denotes a swivel base mounted on a truck A so that it can rotate freely; 2, a boom whose base end is pivotally connected to the swivel base 1 in a manner that it can be raised and lowered; and 3, interposed between the swivel base 1 and the boom 2 at an appropriate position. This hydraulic cylinder 3 has a load holding side oil chamber 4 (in this example, the non-piston rod side oil chamber) and a load non-holding side oil chamber 5 (in this example, the piston rod side oil chamber). )
The boom 2 is driven to rise and fall by supplying and discharging hydraulic oil to and from the control valve 6. As is well known, in the oil passage 7 that connects the load holding side oil chamber 4 of the hydraulic cylinder 3 and the control valve 6, hydraulic oil can freely flow in the direction of the hydraulic cylinder 3, but the flow in the opposite direction is caused by non-load holding. A counterbalance valve 7a is provided which is configured to be activated when the pressure in the oil passage between the side oil chamber 5 and the control valve 6 exceeds a certain level. Figures 1 and 2
In the figure, 8 is a pressure transducer that converts the oil pressure in the load holding side oil chamber 4 of the hydraulic cylinder 3 into an electrical signal. Referring to FIG. 2, the configuration of the boom moment response electric signal generating device of the present invention will be explained. The electrical output signal generated by the pressure transducer 8 enters a computing unit 9. 10
is the raising and lowering driving state of the boom 2, that is, the hydraulic cylinder 3 is extended and the boom 2 is raising and lowering, the hydraulic cylinder 3 is contracting and the boom 2 is lowering and lowering, or the hydraulic cylinder 3 is stopped. This is a boom hoisting drive direction detector that detects whether the boom 2 is stopped. Specifically, the boom hoisting drive direction detector 10 is configured with a limit switch (not shown) arranged in relation to the control valve 6 so as to detect the operating state of the control valve 6, or a limit switch (not shown) that is arranged in relation to the control valve 6, or An angle transducer 11 that detects the angle and generates it as an electrical signal, and a discriminator 12 that discriminates whether the electrical signal generated by the angle transducer 11 is increasing or decreasing within a minute unit time. Just configure it. 13 is a correction signal generation section, and this correction signal generation section 13
is the hydraulic cylinder 3 when the boom 2 is driven to raise and lower.
An electric signal corresponding to the frictional resistance force generated between the cylinder and the piston and between the cylinder and the piston rod is stored in advance as a correction electric signal, and the boom hoisting drive direction detector 10 detects the raising or lowering movement of the boom 2. When detected, a correction electrical signal corresponding to the detection result is generated. This generated correction electric signal is supplied to the arithmetic unit 9. The calculator 9 corrects (amplifies, if necessary) the electrical signal supplied from the pressure transducer 8 in accordance with this corrected electrical signal to generate an electrical signal responsive to the boom moment. In the case of this embodiment, the correction signal generated from the correction signal generating section 13 is set as follows.

That is, the boom hoisting drive direction detector 10 detects the hoisting motion of the boom 2, and the signal is sent to the correction signal generator 13.
If it is in.

In this case, hydraulic oil is supplied to the load non-holding side oil chamber 5 of the hydraulic cylinder 3, and the hydraulic oil is discharged from the load holding side oil chamber 4. A constant pressure Pc sufficient to open the counterbalance valve 7 is generated. Furthermore, when the hydraulic cylinder 3 is retracting, the frictional force f that exists in the oil-tight sliding portion between the piston and cylinder of the hydraulic cylinder and between the piston rod and cylinder acts in a direction that inhibits the retracting movement of the hydraulic cylinder 3. . And now, the external force acting on the hydraulic cylinder 3 ; F Pressure in the oil chamber 4 on the load holding side ; P Area of the oil chamber on the load holding side ; S Pressure in the oil chamber 5 on the non-load holding side ; Pc Area of the oil chamber on the non-load holding side ;sc Frictional resistance force between the cylinder, piston, and piston rod ;f Assuming that, the following equation holds true.

F=SP-ScPc+f The electric signal corresponding to (-ScPc+f) in this equation is a value stored in advance in the correction signal generation unit 13 as a correction electric signal when the boom is lowered. When the driving direction detector 10 detects the overturning motion of the boom 2, the correction signal generator 13 outputs the signal. Then, in the computing unit 9, the electric signal output from the pressure transducer 8 is added and corrected by the above-mentioned value, so that the signal obtained from the computing unit 9 is calculated based on the external force acting on the hydraulic cylinder 3 (this is the boom moment). (which is the value it responds to).

The boom raising/lowering drive state detector 10 detects the raising/lowering of the boom 2, and the signal is sent to the correction signal generator 13.
If it is in.

In this case, the load holding side oil chamber 4 of the hydraulic cylinder 3
Hydraulic oil is supplied to the oil chamber 5 on the non-load-holding side, and is discharged from the oil chamber 5 on the non-load-holding side.The balance of forces in the hydraulic cylinder 3 is expressed in the formula using the same signs as above:F=SP-ScPc −f However, in this case, Pc is at an extremely low pressure, so
The term ScPc can be ignored, and the following equation holds.

F=SP-f The electric signal corresponding to -f in this equation is a value stored in advance in the correction electric signal generation unit 13 as a correction electric signal when the boom is raised. When the drive direction detector 10 detects the raising and raising of the boom 2, the correction signal generator 13 outputs the signal. Then, in the arithmetic unit 9, the value is added and corrected to the electric signal output from the pressure transducer 8, so that the signal obtained from the arithmetic unit 9 is
It responds almost accurately to the external force (boom moment response value) that acts on the boom.

In the above embodiment, the correction signal generating section stores and outputs the value obtained by adding the pressure of the oil chamber on the non-load holding side of the hydraulic cylinder to the frictional force f between the cylinder, piston, and piston rod.
Of course, the correction signal generating section may be configured to memorize and output only the value of the frictional resistance force f, and the oil pressure in the oil chamber on the non-load holding side may be detected by a pressure transducer.

As is clear from the above description, when the boom is being raised and lowered, the frictional resistance force f between the cylinder, piston, and piston rod is in the opposite direction to the external force F acting on the hydraulic cylinder. In order to take this frictional resistance into consideration, the present invention is equipped with a boom hoisting drive direction detector and is configured to correct the electrical signal generated by the pressure transducer according to the detection result of this detector. Since it is possible to obtain an accurate boom moment response electrical signal, its practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a truck crane, and FIG. 2 is a boom moment response electric signal generator according to the present invention. Hydraulic cylinder; 3. Pressure transducer;
8. Boom hoisting drive direction detector; 10.

Claims (1)

[Scope of utility model registration request] A boom moment response electric signal generator for a work vehicle having a boom such as a crane having a boom controlled by a double-acting hydraulic cylinder,
A pressure transducer that converts the hydraulic pressure in the load holding side oil chamber of the hydraulic cylinder into an electric signal corresponding to the hydraulic pressure, a boom hoisting drive direction detector, and at least between the cylinder and the piston of the hydraulic cylinder when the boom is hoisted. and a correction signal generating section that stores in advance an electric signal corresponding to the frictional resistance force generated between the cylinder and the piston rod as a correction electric signal, and the boom hoisting drive direction detector detects the raising or lowering movement of the boom. When detected, outputting a correction electric signal corresponding to the detection result from the correction signal generator,
A boom moment response electric signal generator for a working vehicle having a boom such as a crane, characterized in that the electric signal generated by the pressure transducer is corrected in response to the correction electric signal from the correction signal generator. .