JPH11322261A - Hanging load calculating method in hydraulic shovel of crane specification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly calculate hanging load and secure safety by judging an operating state of an attachment from a change at each detection tip and interrupting a new calculation by holding arithmetic values of hanging load calculated till the time when the attachment becomes a stoppage state for prescribed time or more. SOLUTION: An operating state of an attachment 10 is monitored by booms by angle sensors 17, 18 and changes in arm angles θ1, θ2. When movement of the attachment 10 is stopped, the time elapsed after the stoppage is measured by a timer and whether the stoppage state is continued for prescribed time or more or not is judged. When the attachment 10 is moving in the vertical direction and the stoppage time is less than the prescribed time, hanging load Wx is calculated. When the attachment 10 is in the stoppage state for the prescribed time or more, bottom pressure P1 of a boom cylinder 12 is lowered by the time elapsed after the stoppage and a possibility that hanging load can not be exactly calculated exists. Therefore, arithmetic values of hanging load calculated till the time are held and a new calculation is interrupted, and if hanging load should exceeds rated load, an alarm is given.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a suspension load in a hydraulic excavator of a crane specification, and more particularly to a suspension load of a hydraulic excavator of a crane specification equipped with a safety valve when a hydraulic hose is broken. It relates to an arithmetic method.

[0002]

2. Description of the Related Art There is a case where a hanging hook is attached to a tip of an attachment of a hydraulic excavator, and a suspended load is locked to the hanging hook to be used as a crane. Such a crane-type hydraulic excavator detects the boom angle and the arm angle with an angle sensor, detects the bottom pressure and rod pressure of the boom cylinder with a pressure sensor, and calculates the lifting load and the rated load from each detected value. The calculation is performed and an alarm is issued when the suspended load exceeds the rated load.

[0003] Further, it is obligatory for the hydraulic excavator of the crane specification to equip a boom lowering line with a safety measure valve in case of a hydraulic hose breakage. The safety measure valve includes a check valve, a switching valve, and the like, and is provided near the boom cylinder. And
Even if the hydraulic hose breaks and hydraulic oil leaks out, the hydraulic oil in the boom lowering line is shut off by the check valve inside the safety measure valve to prevent the attachment and the suspended load from falling.

[0004]

However, when the movement of the attachment is stopped and the boom is held, there is a slight leak from the switching valve of the safety measure valve, and the leak gradually reduces the pressure of the boom cylinder. Down to
When the limit of the frictional force of the cylinder rod is exceeded, the boom lowers by a small amount. As described above, since the holding pressure of the boom is reduced due to the leakage of the safety valve, if the attachment is stopped and the holding time is prolonged, the calculated value of the hanging load becomes smaller than immediately after the stop even for the same hanging load. Therefore, when an alarm is issued with the suspended load slightly exceeding the rated load, if the attachment is stopped and left in this state, there is a problem that the alarm stops as time passes.

[0005] Therefore, in a hydraulic excavator of a crane specification, there is a technical problem to be solved in order to accurately calculate a suspension load and to ensure safety even when hydraulic oil leaks from a safety measure valve. The present invention aims to solve this problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been proposed to achieve the above object, and has a hanging hook attached to the tip of the attachment and a safety measure valve in the event of a hydraulic hose breakage in the boom lowering line. It is configured to calculate the suspended load and the rated load from the detected values of the boom angle and the arm angle and the detected values of the bottom pressure and the rod pressure of the boom cylinder, and to issue an alarm when the suspended load exceeds the rated load. In a hydraulic excavator of a crane specification, the operation state of the attachment is determined from the change in each of the detection values, and when the attachment has stopped for a predetermined time or more, the calculated value of the suspended load calculated up to that time is held. The present invention also provides a method of calculating a suspended load in a hydraulic excavator of a crane specification in which a new calculation is interrupted.

[0007]

An embodiment of the present invention will be described below in detail with reference to the drawings. For convenience of explanation, conventionally known components will be described at the same time. FIG. 1 shows a control circuit in a hydraulic excavator of a crane specification, and an attachment 10 has a boom cylinder 1 for moving a boom 11 up and down.
2, an arm cylinder 14 for rotating the arm 13,
A bucket cylinder 16 for opening and closing the bucket 15 is provided. An angle sensor 17 is provided at a rotation base of the boom 11, and an angle sensor 1 is provided at a rotation base of the arm 13.
8 is provided to detect the boom angle theta ₁ and the arm angle theta ₂ to input detection signal of the angle sensor 17 and 18 respectively to the controller 19. Further, the respective pressure sensors 20, 21 provided on the bottom side and the rod side of the boom cylinder 12, for detecting the bottom pressure P ₁ and the rod pressure P ₂ of the boom cylinder 12 inputs the detection signal respectively to the controller 19.

The hydraulic oil discharged from the hydraulic pump 25 is:
In addition to being supplied to the control valve 30 for the boom and the control valve 40 for the bucket, it is also supplied to a control valve (not shown) for the arm. The control valve 30 for the boom is controlled by operating a remote control valve 31, and an HBCV (Hose Burst Check Valve) 32 is installed as a safety measure valve close to the boom cylinder 12 on the bottom line L ₁ of the boom cylinder 12. A holding valve 33 is interposed between the HBCV 32 and the control valve 30.

[0009] A two check valves 34 and 35 to the HBCV32 is provided in parallel, one pilot type check valve 34, the reverse flow when the pilot pressure P ₃ of the pilot line L ₃ is zero It becomes possible. Further, a switching valve 36 is interposed on the pump side of the check valve 34. The switching valve 36 is normally in the closed position 36a, and switches to the throttle position 36b when a pilot pressure is applied to the pilot port 37. When accordingly the pilot pressure P ₃ becomes zero the pilot line L ₃ is communicated with the tank 50. The switching valve 3
6 pilot port 37 of the pilot line L ₅ of the boom lowering side of the remote control valve 31 is connected. Further, reference numeral 38 denotes a relief valve to open when the bottom line L ₁ is equal to or higher than the pressure specified.

When the remote control valve 31 is operated to the boom raising side 31a, the pilot line L ₄
Pilot pressure P ₄ is generated, switches the position 30a the control valve 30 is raised to. When accordingly, the working oil is led out to the bottom line L ₁ of the boom cylinder 12 reaches the HBCV32 through retention valve 33, the H
It is supplied to the bottom side of the boom cylinder 12 through the check valve 35 of the BCV 32. Accordingly, the boom cylinder 12 is extended, the working oil of the rod side of the boom cylinder 12 is returned to the tank 50 through the rod line L _2. Thus, the boom 11 rises.

On the other hand, when the remote control valve 31 is operated to the boom lowering side 31b, the pilot line L
₅ the pilot pressure P ₅ is generated in the control valve 30 is switched to position 30b down. When accordingly the hydraulic oil is led to the rod line L ₂ boom cylinder 1
2 is supplied to the rod side. Therefore, the boom cylinder 1
2 is contracted, the working oil in the bottom side of the boom cylinder 12 reaches the HBCV32 through the bottom line L _1.

[0012] As described above, the pilot port 37 of the switching valve 36 is connected to pilot line L _5, since when boom lowering is switched to position 36b switching valve 36 is squeezed by the pilot pressure P _5, pilot lines the pilot pressure P ₃ of the L ₃ opens the check valve 34 becomes zero, it is possible to reverse flow of the bottom line L _1. Accordingly, the hydraulic fluid on the bottom side passes through the check valve 34 and the switching valve 36, and returns to the tank 50 through the holding valve 33 and the control valve 30. Thus, the boom 11 descends.

Meanwhile, the control valve 40 for the bucket is controlled by the operation of the remote control valve 41, the pilot pressure P ₆ in the pilot line L ₆ when the remote control valve 41 is operated in a bucket closing side 41a is generated The control valve 40 switches to the closed position 40a. In that case, the hydraulic oil is supplied to the bucket cylinder 16
Is derived to the bottom line L _8, the bucket cylinder 16
Extend, and the bucket 15 assumes a closed posture as shown in the figure.

[0014] In contrast, when the remote control valve 41 is operated in a bucket opening side 41b is pilot pressure P ₇ is generated in the pilot line L _7, switched to position 40b the control valve 40 is opened. When that happens,
Hydraulic oil is derived to the rod line L ₉ of the bucket cylinder 16, although not shown, the posture opens the bucket 15 bucket cylinder 16 is contracted.

[0015] Here, Yes and interposed electromagnetic switching valve 42 in the middle of the pilot line L _7, the controller 1
9 is input, the electromagnetic switching valve 4
2 switches from the open position 42a to the closed position 42b.
Therefore, when the hanging hook 22 is attached to the attachment 10 to make the crane specification, the electromagnetic switching valve 42 is switched to the closed position 42b to switch the pilot line L _7.
And the remote control valve 41 is turned to the bucket open side 41b.
In such a case, the bucket 15 is regulated so as not to open even if it is accidentally operated.

Reference numeral 26 denotes a relief valve for regulating the discharge pressure of the hydraulic pump 25, and reference numeral 27 denotes a hydraulic pressure source for a remote control valve. Further, reference numeral 60 is a monitor for displaying the suspension load W _X and load rating W _M or the like which is computed, 61 buzzer for issuing an alarm, 62 is a lamp for alarm. The controller 19 detects a bottom pressure P ₁ and the rod pressure P ₂ of the boom angle theta ₁ and the arm angle theta ₂ and the boom cylinder 12, with determining the operation state of the attachment 10 from the change of the detection value, respectively Rated load W _M
It calculates a load W _X hanging with. Also displays selectively or simultaneously the monitor 60 a distance d _X etc. until the fulcrum hanging load W _X and the rated load W _M sequence hanging computed.

[0017] As will be described later, compares the suspended load W _X and the rated load W _M by the controller 19, when the suspended load W _X has exceeded the rated load W _M is, or lighting the lamp 62 together with sounding the buzzer 61 It is configured to emit an alarm by flashing to notify the operator of an overload.

Further, a switch 63 for designating a normal shovel-specific operation and a crane-specific operation is provided, and the operator inputs the operation specification to the controller 19 using the switch 63. The controller 19 determines whether the excavator specifications or crane specification by operating the switch 63 does not execute the operation process and the warning process in suspension load W _X For excavator specifications. When the attachment 10 is set to the crane specification, the operator preliminarily closes the bucket 15 to the maximum state. However, the controller 19 outputs a signal to the electromagnetic switching valve 42 when determining that the bucket 15 is the crane specification. 42 is switched to the closed position 42b to hold the bucket 15 in the closed position.

[0019] Next, a description will be given of a procedure for calculating the suspension load W _X. As shown in FIG. 2, the rotational moment M acting on the attachment 10
And the distance D from the boom foot 11 a to the axis of the boom cylinder 12.

[0020]

(Equation 1)

The rotational moment M ₀ when the attachment 10 is in the current position shown in the figure and there is no suspended load is

[0022]

(Equation 2)

[0023] from equation (1) and equation (2), the moment M _X generated by the hanging load W _X is,

[0024]

(Equation 3)

Therefore, the lifting load W _X is expressed by the following equation.

[0026]

(Equation 4)

In a crane-type hydraulic excavator,
For each model according to the posture of the attachment 10, and pre-load rating W _M are determined, the distance to the hanging fulcrum d _X
Rated load W _M as the increases will be small.

Here, the remote control valve 31 shown in FIG.
When stopping the vertical movement of the boom 11 in the neutral position, since the pilot pressure P ₅ in the pilot line L ₅ do not occur, the switching valve 36 becomes closed position 36a in the HBCV32, pilot pressure in the pilot line L ₃ Since P ₃ is generated, the check valve 34 is closed, and backflow from the bottom side of the boom cylinder 12 is prevented. Thus, the bottom line L ₁ is blocked boom 11 is held in a stopped state.

However, the switching valve 36 has a slight leakage due to its structure, and it is extremely difficult to eliminate the leakage.
Therefore, even when the switching valve 36 is in the closed position 36a, switching valve 3 from the pilot line L ₃ of the hydraulic fluid on the bottom side of the boom cylinder 12 is the check valve 34
6 to the tank 50.

Accordingly, as shown in FIG. 3, the bottom pressure P ₁ of the boom cylinder gradually decreases, and the boom 11 lowers by a small amount at time t when the frictional force f of the cylinder rod exceeds the limit. In terms of the frictional force f, immediately after the movement of the boom 11 is stopped, only the kinetic frictional force that has been moving up to that point, the frictional force f is extremely small. In contrast, the holding time to stop the boom 11 becomes longer changes from kinetic friction static friction, and by oil leakage in HBCV32 described above, since the bottom pressure P ₁ decreases with time, the cylinder rod The frictional force f becomes maximum immediately before the movement starts.

When the boom 11 is lowered, the bottom volume of the boom cylinder 12 is reduced, and the bottom pressure P ₁ is increased again by the volume reduction, so that the boom 11 is stopped from lowering. Thus, in the state holding the boom 11 to stop the movement of the attachment 10, the bottom pressure P ₁ of the boom cylinder repeats the change.

Here, considering the frictional force f of the cylinder rod, the above-described rotational moment M is expressed by the following equation.

[0033]

(Equation 5)

However, the cylinder which changes every moment during the operation
Since it is impossible to detect the frictional force f of the rod,
The rotational moment M is calculated by the above equation (1). This
Immediately after stopping the movement of the attachment 10
Load W_XCan be calculated accurately, but the elapse of time after stopping
With the bottom pressure P₁Load W _X
Cannot be calculated accurately. Movement of attachment 10
Stop, the boom 11 exceeds the limit of the frictional force f
The time up to the point t when the descent starts
And the lifting load, but according to the applicant's experimental results
It turns out that boom 11 starts to descend in a few minutes
You.

[0035] Therefore, in order to accurately calculates the load W _X suspension in the present invention performs an operation of lifting the load W _X in accordance with the flowchart shown in FIG. First, the boom angle θ ₁ and the arm angle θ ₂ are detected by the angle sensors 17 and 18 (Step 1), and the bottom pressure P ₁ and the rod pressure P ₂ of the boom cylinder 12 are detected by the pressure sensors 20 and 21 ( Step 2). Attachment 10 from one set based on each detected value
Thereby calculating the rotational moment M (Step 3), and calculates the distance d _X to hanging fulcrum to determine the orientation of the attachment 10 (Step 4). The hydraulic excavator of the crane specification, for each model according to the posture of the attachment 10, has previously rated load W _M are determined, calculating the rated load W _M in this state if the distance d _X to hanging fulcrum is known Yes (step 5).

Next, the operation state of the attachment 10 is monitored based on changes in the boom angle θ ₁ and the arm angle θ ₂ , and when the movement of the attachment 10 is stopped, the elapsed time after the stop is measured by a timer. It is determined whether or not the stop state has continued for (n seconds) or more (step 6). The attachment 10 is moving up and down, or the attachment 1
0 downtime is less than n seconds, calculates a load W _X suspended by four expressions described above (step 7). If in step 6, since the attachment 10 is when it is stopped or n seconds, there is a risk that can not be accurately calculated the suspension load W _X with the passage of after the stop time, operation up to that time The calculated value of the suspended load is held, and the new calculation is interrupted. The predetermined time of n seconds differs depending on the model of the excavator and the lifting load, but is set to about 30 seconds.

[0037] In step 8, compares the rated load W _M calculated in step 5, and a suspension load W _X calculated in step 7, event, when the suspension load W _X exceeds the rated load W _M is As described above, the buzzer 61 is sounded and the lamp 62 is turned on or blinked to issue an alarm (step 9) to notify the operator of the overload. On the other hand, load W _X hanging in step 8 is equal to or less than the rated load W _M, jump to step 10. Then, in step 10, to display selectively or simultaneously the monitor 60 a distance d _X etc. until fulcrum hanging the suspension load W _X and the rated load W _M sequence (Step 9). Incidentally, in step 8, when the suspension load W _X approaches the rated load W _M be equal to or less than the rated load W _M may be issued a warning as a pre-stage of the alarm. Buzzer 61 for warning and warning
And the lighting color of the lamp 62 are changed.

[0038] Here, in step 6, the attachment 10 by a change in boom angle theta ₁ and the arm angle theta ₂
Although There has to determine whether or stopped in operation, In addition, the change of the bottom pressure and the rod pressure of the boom cylinder 12 and arm cylinder, a change in the operating state and suspension load W _X of the attachment 10 determination You can also. Further, when the attachment 10 is in operation, since the bottom pressure P ₁ and the rod pressure P ₂ of the boom cylinder 12 is not stable, during which without operation suspension load W _X, n seconds attachment 10 has stopped it may be calculated the load W _X suspension until.

Thus, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

[0040]

According to the present invention, as described in detail in the above embodiment, in a crane type hydraulic excavator equipped with a safety measure valve in case of a hydraulic hose breakage, the attachment has been stopped for a predetermined time or more. Sometimes, the new calculation of the suspension load is interrupted, so even if hydraulic oil leaks from the safety valve while holding the attachment, the suspension load is accurately calculated. be able to. Thus, the alarm stop due to the calculation error of the suspension load is eliminated, and the safety of the work in the crane-type hydraulic excavator can be ensured.

[Brief description of the drawings]

 The figure shows an embodiment of the present invention.

FIG. 1 is a control circuit diagram of a hydraulic excavator of a crane specification.

FIG. 2 is an explanatory diagram showing a rotational moment and a hanging load acting on an attachment.

FIG. 3 is a graph showing changes in bottom pressure of a boom cylinder and frictional force of a cylinder rod.

FIG. 4 is a flowchart showing a procedure for calculating a hanging load.

[Explanation of symbols]

10 Attachment 11 boom 12 boom cylinder 13 the arm 15 the bucket 17, 18 an angle sensor 19 controller 20, 21 pressure sensor 22 hanging hook 32 HBCV (hose burst check valve) 61 Buzzer 62 lamp theta ₁ boom angle theta ₂ arm angle P ₁ bottom pressure P ₂ rod pressure

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[Procedure amendment]

[Submission date] May 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Further, a switch 63 for designating a normal shovel-specific operation and a crane-specific operation is provided, and the operator inputs the operation specification to the controller 19 using the switch 63. The controller 19 determines whether the excavator specifications or crane specification by operating the switch 63 does not execute the operation process and the warning process in suspension load W _X For excavator specifications. When the attachment 10 is set to the crane specification, the operator preliminarily closes the bucket 15 to the maximum state. However, the controller 19 outputs a signal to the electromagnetic switching valve 42 when determining that the bucket 15 is the crane specification. 42 is switched to the closed position 42b is kept in the closed position of the bucket 15.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

[0037] In step 8, compares the rated load W _M calculated in step 5, and a suspension load W _X calculated in step 7, event, when the suspension load W _X exceeds the rated load W _M is As described above, the buzzer 61 is sounded and the lamp 62 is turned on or blinked to issue an alarm (step 9) to notify the operator of the overload. On the other hand, load W _X hanging in step 8 is equal to or less than the rated load W _M, jump to step 10. Then, in step 10, to display selectively or simultaneously the monitor 60 a distance d _X etc. until fulcrum hanging the suspension load W _X and the rated load W _M sequence. Incidentally, in step 8, when the suspension load W _X approaches the rated load W _M be equal to or less than the rated load W _M may be issued a warning as a pre-stage of the alarm. The alarm and the warning are distinguished by changing the sounding pattern of the buzzer 61 and the lighting color of the lamp 62.

Claims (1)

[Claims] 1. A hanging hook is attached to a tip end of an attachment, and a safety measure valve is provided in a boom lowering line when a hydraulic hose is broken, and a detected value of a boom angle and an arm angle, and a bottom pressure and a rod pressure of a boom cylinder are reduced. Calculate the lifting load and the rated load from the detected values, and in a crane-type hydraulic excavator configured to issue an alarm when the lifting load exceeds the rated load, the operating state of the attachment is determined from the change in each of the detected values. Judgment, when the attachment has been stopped for a predetermined time or more, a new calculation is suspended while retaining the calculated value of the suspended load calculated up to that time. Calculation method of lifting load.