JP2008096255A - Apparatus for measuring load of working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus capable of solving insufficiency in the accuracy of Japanese Unexamined Patent Application Publication No. 2006-78348, while taking advantage of its strong points. <P>SOLUTION: The apparatus is constituted of a boom 3, an arm 4, angle sensors 7-9 for measuring respective rocking angles of a working tool 5, pressure sensors 10a and 10b for detecting a pressure of a boom cylinder 3a, a load cell 25 with a load limiting function which is coupled at the tip of a working tool cylinder 5a and provided to a link 11 for rocking the tool 5, and an arithmetic operation means 6 for calculating the load of cargo from respective detection values of the angle sensors 7-9, the pressure sensors 10a and 10b, and the load cell 25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a load measuring device for a work machine.

  In a working machine such as a hydraulic excavator, the work amount may be measured by an integrated value of a load transported by a work tool. For example, in the case of a work that attaches a magnet or the like as a work tool to the tip of a work device to which the boom or arm is connected, and picks up and lifts iron scrap or the like as a suspended load, the integrated value of the load of the suspended load to be absorbed Will be measured. Conventionally, as a load measuring device in such an aspect, a technique disclosed in Japanese Patent Laid-Open No. 2002-277311 (Patent Document 1) has been proposed. As shown in FIG. 10, a pin type load cell is incorporated at two locations of the pins 100 and 101 of the work tool connecting portion at the tip of the arm 4 and the link tip connected to the boom cylinder, and acts on the two pins. The resultant force of the forces Ta and Tc is calculated to calculate the suspension load W of the work tool.

  However, this technique assumes that there is a suspended load at the center of the magnet 102, which is a work tool, so that the load measurement accuracy is not always good, and a load cell is arranged on the front end side of the front work device. Therefore, as a result of using a structure with an excessive capacity in consideration of overload on the load cell, the load measurement accuracy decreases, the durability problem from the structure of the pin type load cell, and the load cell itself when replacing the work tool There existed a problem that there was a high possibility of damage from the necessity to remove. For this reason, the applicant of this application has proposed the load measuring apparatus which can solve these problems in Unexamined-Japanese-Patent No. 2006-78348 (patent document 2).

This device includes an angle sensor for measuring each rotation angle of a boom, an arm, and a work tool, a pressure sensor for detecting a pressure of the boom cylinder and the work tool cylinder, and an arm from each detection value of the angle sensor and the pressure sensor. Computation processing means that calculates moments around the tip pin and calculates the suspension load from them, and according to this, unlike the above technique, the load cell is arranged on the pin part that is the support part of the work tool Since this is not done, all the problems arising from the load cell will be solved.
Japanese Patent Laid-Open No. 2002-277311 (FIG. 4) Japanese Patent Laying-Open No. 2006-78348 (FIG. 3)

  On the other hand, in this technique, the member closest to the work tool among the members to be detected for calculating the suspension load of the work tool is the work tool cylinder (usually a bucket cylinder). Since the load on the work tool is small, the moment calculation value around the work tool connecting pin varies greatly due to a slight change in pressure, and there is a problem that the detected value varies depending on the position of the load with respect to the work tool.

  The present invention was devised in view of the above-described problems of the prior art, and provides an apparatus that can solve the inadequate accuracy that is the subject while taking advantage of the advantages of JP-A-2006-78348. It is something to try.

  For this reason, the load measuring device for a work machine according to the present invention is a load measuring device for a work machine in which an arm is connected to a boom end and a work tool is swingably connected to the arm end. , An angle sensor that measures each swing angle of the work tool, a pressure sensor that detects the pressure of the boom cylinder, and a load limiter that is connected to the tip of the work tool cylinder and disposed at a link portion that swings the work tool. It is characterized by comprising a load cell with a function, and arithmetic processing means for calculating the load of the load from the detected values of the angle sensor, the pressure sensor and the load cell.

  The present invention basically adopts the device configuration proposed in Japanese Patent Laid-Open No. 2006-78348, but in that configuration, a load cell with a load limiting function is used instead of a configuration for detecting the pressure of the work implement cylinder, It arrange | positions to the link part (for example, link rod) which rocks a working tool. The link portion that swings the work tool is a member that is connected to the work tool, and is a member that receives the load of the load as it is. For this reason, the load cell detected at that position can detect the load value around the link appropriately corresponding to the load value of the load, and the error of the load value of the load that is finally calculated based on that value is extremely small. Less. On the other hand, since a load cell with a load limiting function is used, even if an excessive load occurs near the work tool, the load cell receives it by means of the load limiting function, so a structure with an especially excessive load rating There is no need to use For this reason, the thing of the rating suitable for the load of a load can be used, and the detection accuracy improves.

  Here, as a form accompanied with the load limiting function of the load cell, as in the embodiment described later, the load cell is arranged after the load limiting function is provided in the link portion, and the load cell itself is loaded. It is good also as a structure provided with a restriction | limiting function. As a specific aspect of the load limiting function, there is a structure in which the load cell main body or the main body attaching portion is provided with a load restricting body movement limiting mechanism with respect to the load cell detecting portion.

  According to the above configuration, the load measurement value error is reduced regardless of the position of the work implement. In addition, the load cell to be applied may be rated so that the load value of the assumed load can be detected, so that the accuracy of load measurement is not reduced. That is, the present invention overcomes the problems of the conventional load measuring device and can perform load detection with sufficient accuracy.

  An example of a specific form according to the present invention will be described with reference to the drawings. In the following example, a hydraulic excavator is used as a base machine, and the working tool is in the form of using a magnet. However, this may be applied to other types of working machines (for example, the working tool is a small turning type of a bucket). Of course, the present invention is not limited to the following embodiments.

  FIG. 1 shows a load detection device and a hydraulic excavator to which the load detection device is applied. As shown in the figure, in the excavator, an upper swing body 2 is connected to a lower traveling body 1 so as to be horizontally rotatable, and a front work device as a work device is attached to the upper swing body 2. The front working device is composed of a boom 3, an arm 4, and a magnet 5 as a work tool. The boom 3 is mounted on a bracket (not shown) of the fuselage, the arm 4 is mounted on the end of the boom 3, and the magnet 5 is mounted on the end of the arm 4. The hydraulic cylinders (boom cylinder 3a, arm cylinder 4a, work tool cylinder 5a) are connected by pins 7a to 9a, respectively, and can be swung around the connection pins 7a to 9a as base points. The magnet 5 carries a load by adsorbing scraps such as iron scraps, and is swingable around the arm connecting pin 9a by a link rod 11 connected to the tip of the work tool cylinder 5a. Further, the magnet 5 includes an electromagnetic magnet control panel 17, and excitation is turned on / off by the switch mechanism 18.

  The load detection device consists of an angle sensor 7-9 attached to the boom 3, the arm 4, and the magnet 5, which is a work tool, a pressure sensor 10 (10a, 10b) for detecting the pressure of the boom cylinder 3a, and the magnet 5 around A load cell 25 for detecting the load of the link portion, and a controller 6 for calculating a suspension load based on the detection values output from them.

  The angle sensors 7 to 9 detect the swing angles of the boom 3, the arm 4, and the magnet 5, which are movable members. The swing angle is the boom angle α as the joint angle of the boom 3 with respect to the upper swing body 2, the arm angle β as the joint angle of the arm 4 with respect to the boom 3, and the joint angle of the magnet 5 with respect to the arm 4 (originally the bucket). As the bucket angle γ.

  The pressure sensors 10 (10a, 10b) are arranged at two locations on the head side and the rod side of the boom cylinder 3a, and detect pressures (head pressure and rod pressure) at the respective positions.

  As shown in FIG. 2, the load cell 25 is incorporated in a link rod 11 that is a link member of the magnet 5. The link rod 11 is pivotally supported at both ends by a connecting pin 5b to the magnet 5 and a connecting pin 5c to the work tool cylinder 5a.

  Such a load cell 25 built-in structure of the link rod 11 is a load limiting structure for preventing an excessive load from being applied to the load cell 25. That is, as shown in the figure, the link rod 11 is composed of a casing 20 and a shaft 21, and the shaft 21 is slidably coupled within the casing 20 (the end of the shaft 21 is connected to the shaft by a connecting pin 5b). The end of the casing 20 is pivotally supported by the connecting pin 5c). The front end of the shaft 21 is formed with a front end flange by a plate member 22 fastened with bolts. On the other hand, the casing 20 is formed by joining a main body portion 20a in which an insertion hole into which the shaft 21 is inserted is formed and a fitting portion 20b that closes the insertion hole and pivotally supports the inserted shaft 21. . The inner diameter of the insertion hole of the main body portion 20a is smaller than the flange width of the shaft tip 22, but the diameter of the shaft tip 22 is increased to a predetermined depth to form a stepped portion 20c, and the shaft tip 22 in a state of being inserted into the bottom of the insertion hole. Is locked at the stepped portion 20c. In such a configuration, the load cell 25 is disposed at the distal end of the fitting portion 20b in the insertion hole of the casing 20, and the buffering spring 26 is disposed at the distal end thereof. In the state where the shaft 21 is inserted into the insertion hole, the load cell 25 is sandwiched between the fitting portion 20b of the casing 20 and the flange of the shaft tip 22 via the spring 26 as shown in FIG. Will be placed.

  As a result, when a force in the compression direction acts on the link rod 11 (for example, when the magnet 5 collides with something), the shaft tip 22 comes into contact with the bottom of the insertion hole of the casing 20 and the force is applied to the load cell 25. Does not work. On the other hand, when a force in the pulling direction acts (for example, when a load is attracted to the magnet 5), the force acts on the load cell 25 from the shaft 21 via the spring 26, and the load is detected. When an excessive load is applied due to the unexpected movement of the shaft, the shaft tip 22 slides greatly, and the flange of the tip 22 comes into contact with and engages with the step portion 20c of the insertion hole. Further movement is restricted. That is, the stepped structure that allows this engagement state to function restricts the movement of the shaft tip 22 that is a load applying body with respect to the load cell 25 detection unit, which forms a load limiting mechanism of the load cell 25. In this embodiment, it is not necessary to place a load cell that has an excessive load rating due to this load limiting structure, and if a load cell in a range that is suitable for the total load of the magnet 5 weight and the maximum load lifted by the magnet 5 is applied. Since it is good, the load detection apparatus according to the present embodiment is significantly improved in the detection accuracy of the suspended load as compared with the prior art.

  As shown in FIG. 1, the controller 6 receives the outputs from the angle sensors 7 to 9, the pressure sensors 10a and 10b, and the load cell 25, and calculates the load. For this reason, it is connected so that the output values of these devices can be input, and is provided with a display 12 that outputs the values calculated by itself. Further, on / off outputs from the pressure switch 13, the zero setting switch 14, the measurement switch 15, and the reset switch 16 are received, and arithmetic control described later is performed.

  Next, the calculation theory used when calculating the load in the load detection apparatus constructed as described above will be described with reference to FIGS. The theory is basically the same as that disclosed by the applicant of the present application in Japanese Patent Laid-Open No. 2006-78348 (Patent Document 2) except that the detection value of the load cell is used.

The relationship between the lifting load Wg and the moment ΔMbm due to the load around the boom connecting pin 7a is as follows using FIG.
ΔMbm = Wg ・ (L1 + L2) (1)
L1: Horizontal distance from boom connecting pin 7a to magnet connecting pin 9a L2: Horizontal distance from magnet connecting pin 9a to load point

On the other hand, the relationship between the lifting load Wg and the moment ΔMbk due to the load around the magnet connecting pin 9a is as follows, using FIG.
ΔMbk = Wg · L2 (2)

Therefore, the following equation is obtained from the above equations (1) and (2).
Wg ・ L1 ＝ ΔMbm−ΔMbk (3)

Therefore, the lifting load Wg is calculated by the following equation.
Wg = (ΔMbm−ΔMbk) / L1 (4)

Here, the moment ΔMbm around the boom connecting pin 7a due to the lifting load Wg of the above formula (4) is the moment Mbma around the boom connecting pin 7a under load and the moment Mbmi around the boom connecting pin 7a under no load. Since it is a difference, it is obtained by the following equation.
ΔMbm = Mbma-Mbmi (5)

Here, in the above formula (5), the moment Mbmi around the boom connecting pin 7a at no load is the weight of the boom angle α, arm angle β, bucket angle γ, and movable members 3, 4, and 5 of the front working device. And the position of the center of gravity. That is, when FIG. 4 is used, the moment Mbmi is obtained by the following equation (note that the coordinate position is particularly that shown in FIG. 4. The same applies hereinafter. Wbm is the weight of the boom, Wst is the weight of the arm, Wmg. Is the weight of the magnet).
Mbmi = Wbm.Lob.cos (.alpha. +. Alpha.ab + .alpha.bd) + Wst. {Loa.cos.alpha. + Lac.cos (.pi .-. Alpha .-. Beta .-. Beta.cg)} + Wmg. {Loa.cos.alpha. + Lag.cos (.pi .-. Alpha .-. Beta.) + Lgh.cos (.gamma .-. Gamma.h) -Α-β)} …… (6)

On the other hand, the moment Mbma around the boom connecting pin 7a at the time of load in the above equation (5) is obtained from the pressure (head pressure and rod pressure) of the boom cylinder 3a and the boom angle α. That is, using FIG. 4, the moment Mbma due to the boom cylinder thrust Fbm is obtained by the following equation.
Mbma = Fbm · Lof …… (7)
In the equation (7), the following equation is used.
Lof = Lod · cosη, η = cos -1 {Lod 2 + Lde 2 -Loe 2/2 · Lod 2 · Lde 2},

Next, the moment ΔMbk around the magnet coupling pin 9a due to the lifting load Wg is the difference between the moment Mbka due to the load around the magnet coupling pin 9a under load and the moment Mbki due to the load around the magnet coupling pin 9a under no load. Therefore, it can be obtained by the following formula.
ΔMbk = Mbka-Mbki (8)

Here, in the above equation (8), the moment Mbki around the magnet coupling pin 9a when there is no load is the weight of the boom angle α, arm angle β, bucket angle γ, and movable members 3, 4, and 5 of the front working device. And calculated from the position of the center of gravity. That is, when FIG. 5 is used, the moment Mbki is obtained by the following equation (note that the coordinate position shown in FIG. 5 is used in particular; the same applies hereinafter).
Mbki = Wmg / Lgh / cos (γ + γh−α−β) (9)

∠ｉｋｊ＝φ1となるφ1について、φ1＝cos^−１｛（Lkj^２＋Lki^２＋Lij^２）／２・Lkj・Lki｝、
∠jkg＝φ2となるφ２について、φ２＝cos^−１｛（Lkj^２＋Lkg^２＋Lgij^２）／２・Lkj・Lkg｝、
∠ｉkg＝φとなるφについて、φ＝φ1＋φ2、
モーメントアームＲrod について、Ｒrod＝Lgk・sin（φ） On the other hand, the moment Mbka around the magnet coupling pin 9a at the time of load in the above equation (9) is obtained from the detection value Frod of the load cell 25, the magnet angle γ, and the link mechanism of the magnet cylinder 5a. That is, using FIG. 5, the moment Mbka is obtained by the following equation (Rrod is a moment arm).
Mbka ＝ Frod ・ Rrod …… （10）
In the equation (10), the following equation is used.
For Lkj where kj = Lkj,

For ∠ikj = φ1 become ^{φ1, φ1 = cos -1 {(} Lkj 2 + Lki 2 + Lij 2) / 2 · Lkj · Lki},
For ∠jkg = φ2 become ^{φ2, φ2 = cos -1 {(} Lkj 2 + Lkg 2 + Lgij 2) / 2 · Lkj · Lkg},
For φ where ikg = φ, φ = φ1 + φ2,
For moment arm Rrod, Rrod = Lgk · sin (φ)

  Next, a calculation processing procedure in the controller 6 in which the load is calculated using the above calculation theory will be described with reference to FIGS. The following processing procedure is slightly different from the procedure disclosed in Japanese Patent Laid-Open No. 2006-78348, but may be the same as that.

    FIG. 6 is a flowchart showing the flow of the entire calculation process including offset value calculation, load correction and integration. As shown in the figure, after the load calculation calculation process (S1 to S8) is performed, the magnet 5 is loaded. It is determined whether or not it is adsorbed (S9). If the load is adsorbed, load correction and integration calculation processing are performed (S10 to S14). If it is not the suction state, an offset value calculation calculation process is performed according to the situation (S15 to S19).

  First, although it is load calculation calculation processing (S1-S8), this detailed flowchart is shown in FIG.

(S1)
The data of the weights and the positions of the center of gravity of the movable members 3, 4, and 5 of the front working device are read from the memory in the controller 6.

(S2)
A pressure signal (boom cylinder head pressure Pbmh, boom cylinder rod pressure Pbmr), an angle signal (boom angle α, arm angle β, bucket angle γ) and switch signals input to the controller 6 are read.

(S3)
Of the data read in S1 and S2, the moment around the boom connection pin 7a at the time of no load (the weight of the working device) based on the weight, the position of the center of gravity, and the angle signal of each movable member according to the above equation (6) Mbmi is calculated.

(S4)
Based on the position of the center of gravity, the angle signal, and the pressure signal, the moment Mbma around the boom connecting pin 7a at the time of load is calculated by the above equation (7).

(S5)
Similarly to S3, based on the weight, center of gravity position, and angle signal of each movable member, the moment Mbki around the magnet connection pin 9a at the time of no load (the weight of the working device) is calculated by the above equation (9).

(S6)
Based on the output signal of the load cell 25 and the angle signal of each movable member, the moment Mbka around the magnet coupling pin 9a at the time of load is calculated by the above equation (10).

(S7)
Based on the moments Mbmi, Mbma, Mbki, and Mbka calculated in S3 to 6, the moments ΔMbm and ΔMbk of the boom connecting pin 7a and the magnet connecting pin 9a due to the lifting load Wg are expressed by the above equations (5) and (8). After calculating, based on these calculated moments ΔMbm and ΔMbk, the lifting load Wg is calculated by the above equation (4).

(S8)
Filtering is performed on the value of the lifting load Wg calculated in S7, the fluctuation component is removed, and the average load Wg is calculated. The calculated value is temporarily stored in the memory.

  Thereafter, the process proceeds to a procedure (S9) for determining whether or not a load is attracted to the magnet 5, and the procedure branches depending on whether or not the determination is possible. When the load is adsorbed is the actual lifting load detection state, the procedure in that case will be described with reference to FIG.

(S10)
When a load is attracted to the magnet 5, whether or not the hydraulic excavator is in an operating state is determined based on the presence or absence of a signal from the pressure switch 13. If there is no signal, the process returns to S9.

(S11)
If it is determined in S10 that there is a signal from the pressure switch 13, it is determined whether or not the measurement switch 15 is on. If the measurement switch 15 is not turned on, the process proceeds to step S14 described later.

(S12)
If it is determined in S11 that the measurement switch 15 is turned on, the calculated value of S8 stored in the memory is taken out, the value is corrected with the load offset value, and the final lifting load Wg is calculated. The final value is stored in the memory.

(S13)
It is determined whether or not the magnet operation switch 18 is turned on. If it is determined that the magnet operation switch 18 is turned on, there is a possibility that the operation is still in progress.

(S14)
If it is determined in S13 that the magnet operation switch 15 is not turned on, it is determined that the work for the load has been completed, and the final load value Wg stored in S12 is added to the integrated load. Thereafter, the process returns to the procedure of S2.

  Next, in S9, when it is determined that the load is not attracted to the magnet 5, it is determined that the loading operation is not performed, and the process proceeds to the offset value calculation calculation processing state. The procedure in this state will be described with reference to FIG.

(S15, S16)
It is determined whether or not the reset switch 16 has been operated based on the presence or absence of a switch signal (S15). If a switch signal is input, the integrated load is reset (S16). If no switch signal is input, the process proceeds to step S17.

(S17-19)
Next, the presence / absence of a signal from the pressure switch 13 for detecting the operation state of the hydraulic excavator is determined (S17). If there is a signal, the presence / absence of a signal from the measurement switch 15 is determined (S18). The current load (value calculated in S8) is stored in the memory as a load offset value (S19). If the signal of any of the switches 13 and 15 is not input, the load offset value is not stored, and the process returns to S2.

  As described above, the load calculation process in the controller 6 of this embodiment is based on the calculation method disclosed in Japanese Patent Application Laid-Open No. 2006-78348, and thus the high accuracy of the calculated value of the calculation method itself is exhibited. However, by improving it further, the load around the magnet mounting close to the load that is the final measurement target is detected from the load cell 25, and the detected value is also used as the calculation reference, so it is finally calculated. Value becomes even more accurate, and the occurrence of errors is reduced no matter which part of the magnet 5 is attracted to the load. Here, the load cell 25 is positioned on the front end side of the front working device, and there is a risk of receiving an unexpectedly excessive load due to the operation of the front working device. Is accompanied by a load limiting structure, so an excessive load will not be applied to the load cell 25. For this reason, it is possible to adopt a standard according to the total load of the magnet weight and the maximum load lifted by the magnet 5. There is no fear (opening of accuracy of detection value due to use of a standard with an excessive load taken into account) as in the device of Kai 2002-277311.

  The present invention is a technique applicable to a work machine that requires load detection.

It is explanatory drawing which shows the apparatus structure of the embodiment of this invention. It is explanatory drawing of the load cell incorporating structure used for the example of an embodiment. It is a structure figure for explaining each numerical value used when calculating the moment around the boom attachment pin at the time of load. It is a structural diagram for explaining each numerical value used when calculating the moment around the boom mounting pin when there is no load. It is a structure figure for explaining each numerical value used when calculating the moment around a work implement attachment pin. It is a flowchart of the whole arithmetic processing procedure of a controller. 7 is a flowchart detailing steps S1 to S8 in the flowchart of FIG. 6. 7 is a flowchart detailing steps S10 to S14 in the flowchart of FIG. FIG. 7 is a flowchart detailing steps S15 to S19 in the flowchart of FIG. It is explanatory drawing of the load detection apparatus disclosed by Unexamined-Japanese-Patent No. 2002-277311 (patent document 1).

Explanation of symbols

1 Lower traveling body
2 Upper swing body
3 Boom
3a Boom cylinder
4 arms
4a Arm cylinder
5 Magnet (work implement)
5a Work tool cylinder
6 Controller (arithmetic processing means)
11 Link rod
25 Load cell

Claims (2)

A load measuring device for a work machine in which an arm is connected to a boom end, and a work tool is swingably connected to the arm end.
An angle sensor for measuring each swing angle of the boom, arm, and work implement;
A pressure sensor for detecting the pressure of the boom cylinder;
A load cell with a load limiting function connected to the tip of the work tool cylinder and disposed on a link for swinging the work tool;
Arithmetic processing means for calculating the load of the load from the detected values of the angle sensor, the pressure sensor, and the load cell;
A load measuring device for a work machine, comprising:   The load measuring device for a work machine according to claim 1, wherein a link or a load cell for swinging the work tool is provided with a movement restricting mechanism of the load applying body with respect to the load cell detecting unit.

Images