HYDRAULIC CONTROL SYSTEM IN WORK MACHINES

Abstract

In a work machine in which an interchangeable work attachment is attached to a tip portion of a work arm having a boom, the lowering of the boom is controlled at a lowering speed corresponding to an operation amount of an operating tool in a stable state even when the work attachment is exchanged. A monitoring device (22) for inputting information regarding a weight of an attached work attachment (8) to a control unit (21) is provided. A map (35) indicating a relationship between the weight of the interchangeable work attachment (8) and a holding pressure of an oil chamber (14a) on the cylinder head side of the boom is provided in a control unit (21). An estimated value for the holding pressure corresponding to the weight of the attached work attachment (8) is obtained based on the map (35).A configuration is adopted such that an opening area of ​​a contraction-side discharge port (18f) of a control valve (18) is controlled based on the estimated value of the holding pressure.

Description

Technical field

[0001] The present invention relates to a technical field of a hydraulic control system used in working machines such as a hydraulic excavator. State of the art

[0002] Some work machines such as a hydraulic excavator include a work arm including a boom pivotally mounted on a machine body and capable of swinging vertically, and an arm pivotally mounted in a tip portion of the boom. A work attachment such as a bucket, crusher, and shredder is interchangeably attached to the tip portion of the work arm. A configuration is adopted in which the boom is moved vertically by performing an expansion / contraction operation of a boom cylinder, which expands by supplying oil to a head-side oil chamber and contracts by discharging oil from the head-side oil chamber. In this work machine, a weight of the work arm or the work attachment acts as a force to lower the boom. Accordingly, the pressure in the head-side oil chamber of the boom cylinder is high.Therefore, the lowering speed of the boom is usually controlled by controlling the discharge flow rate from an oil chamber on the boom cylinder head side (discharge control). In this case, for example, a control valve is provided with a discharge port in a discharge oil passage from the oil chamber on the boom cylinder head side, and the area of ​​the discharge port of the control valve is increased or decreased depending on the operation amount of a boom operating tool. In this way, the lowering speed of the boom is controlled to correspond to the operation amount of the operating tool.

[0003] However, when the boom lowering speed is controlled by controlling the discharge flow rate from the oil chamber on the head side of the boom cylinder as described above, the discharge flow rate from the oil chamber on the head side increases or decreases not only depending on the opening area of ​​the discharge port of the control valve, but also on the pressure in the oil chamber on the head side of the boom cylinder. The pressure in the oil chamber on the head side of the boom cylinder changes greatly depending on the weight of the work attachment, which acts as a force to lower the boom. Therefore, the boom lowering speed changes even if the opening areas of the discharge ports are the same, i.e.the operation amounts of the boom operating tools are the same depending on the weight of the attached work attachment, and the lowering speed of the boom cannot be accurately controlled, resulting in a problem of poor operability.

[0004] Therefore, in the related art, for example, the following techniques are known to ensure the lowering speed of the boom according to the operation amount of the operation tool even when the work attachment is replaced. There is a technique (see, for example, PTL 1) described as follows. A control valve (discharge control valve) for controlling the discharge flow rate from the oil chamber on the boom cylinder head side, flow rate detecting means for detecting a flow rate flowing through the control valve, and a pressure sensor for detecting a holding pressure acting on the boom cylinder due to an external force are provided. Based on the detected holding pressure and the detected flow rate, the opening area of ​​the control valve is controlled so that a pressure opposing the holding pressure is generated on an inlet side of the control valve.There is another technique (see, for example, PTL 2) disclosed as follows. An electromagnetic proportional pressure reducing valve is provided in a regeneration circuit to direct the oil discharged from the oil chamber on the boom cylinder head side to an oil chamber on the rod side when the boom is lowered. The opening degree of the electromagnetic proportional pressure reducing valve is controlled based on a differential pressure between the pressure of the head-side oil chamber detected by the pressure sensor and a preset target pressure value of the head-side oil chamber. Patent literature [PTL 1] JP-A-2003-106304 [PTL 2] JP-A-2010-78035 Brief description of the inventionTechnical problem

[0005] However, the two techniques described above, disclosed in PTLS 1 and 2, are configured to control the opening area of ​​the discharge control valve and the opening degree of the electromagnetic proportional pressure reducing valve based on the pressure of the oil chamber on the head side of the boom cylinder, which is frequently input from the pressure sensor. However, the pressure frequently input from the pressure sensor is a dynamic pressure, and there is a possibility that an unstable and unpredictable pressure value is input depending on the usage status of the work attachment. When this dynamic pressure is used, the control valve or the electromagnetic proportional pressure reducing valve is operated irregularly, causing the problem that stable control cannot be performed. Here, this is the problem to be solved by the present invention. Solution to the problem

[0006] In view of the circumstances described above, the present invention was made to solve the problems. According to the invention, in a first aspect, there is provided a boom lowering control system in a work machine including a work arm having at least one boom pivotally supported to swing vertically on a machine body, an interchangeable work attachment attached to a tip portion of the work arm, a boom cylinder that causes the boom to swing vertically by expansion by supplying oil to a head-side oil chamber and contraction by discharging oil from the head-side oil chamber, a control valve having a discharge port for controlling a discharge flow rate from a head-side oil chamber of a boom cylinder, control means for controlling an operation of the control valve, and an operating tool operated to move the boom vertically.The boom lowering control system includes information input means for inputting information regarding a weight of the attached work attachment to the control means. The control means includes a map indicating a relationship between the weight of the interchangeable work attachment and a holding pressure of the oil chamber on the boom cylinder head side, and determines an estimated holding pressure value corresponding to the weight of the attached work attachment based on the map. Based on the estimated value of the holding pressure, the control means controls an outlet opening area of ​​the control valve so that the discharge flow rate from the oil chamber on the boom cylinder head side becomes a target discharge flow rate set in accordance with an operation amount of the operating tool when the boom is lowered.

[0007] According to a second aspect of the invention, in the first aspect of the boom lowering control system in a work machine, when the holding pressure estimated value corresponding to the weight of the attached work attachment is obtained based on the map, the control means groups a holding pressure map value of the oil chamber on the boom cylinder head side into a plurality of groups according to a size of the holding pressure map value to set in advance a representative value of the holding pressure for each group, and sets the representative holding pressure value of a group to which the holding pressure map value corresponding to the weight of the attached work attachment belongs as the holding pressure estimated value corresponding to the weight of the attached work attachment.

[0008] According to the invention in a third aspect, in the first aspect of the boom lowering control system in a work machine, when the estimated holding pressure value corresponding to the weight of the attached work attachment is obtained based on the map, the control means sets a representative value of the holding pressure in advance for each group by grouping the work attachments into a plurality of groups in accordance with a magnitude of the weight of the work attachment, and sets the representative value of the holding pressure of a group to which the attached work attachment belongs as the estimated value of the holding pressure corresponding to the weight of the attached work attachment.

[0009] According to the invention in a fourth aspect, in any one of the first to third aspects of the boom lowering control system in a work machine, the map uses a linear relationship to indicate a relationship between the weight of the work attachment and the holding pressure of the oil chamber on the head side of the boom cylinder based on a moment about a support shaft for swingably supporting the boom on the machine body.

[0010] According to the invention in a fifth aspect, in the first aspect of the boom lowering control system in a work machine, the weight of the work attachment includes the weight of a coupler used to attach the work attachment to the tip portion of the work arm.

[0011] According to the invention in a sixth aspect, in the first aspect of the boom lowering control system in a work machine, the work arm includes the boom and an arm pivotally supported to be pivotable at a tip portion of the boom. As the work attachment, a work attachment attached to the tip portion of the boom and a work attachment attached to a tip portion of the arm are provided. The card when the work attachment is attached to the tip portion of the boom and the card when the work attachment is attached to the tip portion of the arm are provided individually. Advantageous effects of the invention

[0012] According to the invention in the first aspect, the lowering of the boom can be controlled in a stable state at a lowering speed corresponding to an operation amount of the boom operating tool even when the work attachment is replaced. Therefore, the first aspect can significantly contribute to improving operability.

[0013] According to the inventions in the second and third aspects, the lowering of the boom can be controlled more stably, and the second and third aspects are excellent for tuning.

[0014] According to the invention in the fourth aspect, it is possible to easily obtain the holding pressure map values ​​corresponding to the weights of various work attachments.

[0015] According to the invention in the fifth aspect, the holding pressure estimated value is obtained by taking the weight of the coupler into account. Therefore, a correct estimated holding pressure value can be obtained.

[0016] According to the invention in the sixth aspect, even when a working arm forming member to which the working attachment is attached is the boom or the arm, any correct estimated holding pressure value can be obtained. Short description of the drawings Fig. 1 is a side view of a hydraulic excavator. Fig. 2 is a hydraulic circuit diagram of the hydraulic excavator. Fig. 3 is a control block diagram of a boom lowering control system. Fig. 4(A) is a view showing a stem mounting card, and Fig. 4(B) is a view showing a boom mounting card. Fig. Figure 5 is a table showing the grouping of work essays. Description of the embodiments

[0017] In the following, an embodiment of the present invention will be explained with reference to the drawings.

[0018] First, the first embodiment of the present invention will be described with reference to Fig. 1 to 4 explained; Fig. 1 is the drawing illustrating the hydraulic excavator 1 as an example of a construction machine according to the present invention, wherein the hydraulic excavator 1 includes a lower crawler body 2, an upper swing body 3 swingably supported above the lower crawler body 2, and a front working part 4 mounted on the upper swing body 3, and others; and the front working part 4 includes a boom 5 whose base end part is vertically swingably supported by the upper swing body 3, an arm 6 longitudinally swingably supported on one end part of the boom 5, a bucket 7 swingably attached to the end part of the arm 6, and others; wherein the hydraulic excavator 1 includes various hydraulic actuators such as boom / arm / bucket cylinders 8, 9, 10 for swinging the boom 5, the arm 6, and the bucket 7, respectively.of the bucket 7, left and right travel motors (not shown) for moving the lower traveling body 2 and a swing motor (not shown) for swinging the upper swing body 3. In addition, the hydraulic excavator 1 can use various optional hydraulically operated attachments such as a hammer, breaker, grapple and rotary cutter (in . Fig. 1 not shown).

[0019] In addition, reference numeral 14 stands for a boom cylinder that performs an expansion / contraction movement to cause the boom 5 to swing vertically. The boom cylinder 14 is configured as follows. A head-side end portion is supported to swing in a front part of the upper slewing body 3 via a head-side support shaft 14c. A rod-side end portion is supported to swing in an intermediate portion in the longitudinal direction of the boom 5 via a rod-side support shaft 14d. The boom cylinder 14 expands to lift the boom 5 by supplying oil to a head-side oil chamber 14a (in Fig. 1 not shown) of the boom cylinder 14, and contracts to lower the boom 5 by discharging the oil from the head-side oil chamber 14a.

[0020] Fig. 1 shows a bucket mounted as a work attachment 8 at the front end of the working arm 7. However, depending on the work content of the hydraulic excavator 1, various working tools such as a hammer, a compactor, a swing bucket, a clamshell bucket, a thumb bucket, a grapple, and a breaker (all not shown) can be exchanged and mounted at the front end of the working arm 7. When the working tools are mounted at the front part of the working arm 7, in some cases, in contrast to the Fig. 1, no coupler is used. However, in some cases, various couplers (not shown, a pin coupler, a quick coupler, a coupler with a hook, or a coupler that can tilt or rotate the work tool with respect to the work arm) may be used. In addition, when the coupler is used, a combination of the work tool and the coupler can be appropriately selected depending on a function of the coupler. In the present embodiment, when the coupler is used, the work tool and the coupler are referred to as the work attachment 8, and when the coupler is not used, the work tool is referred to as the work attachment 8.

[0021] Fig. 1 also shows the boom 5 and the arm 6 as arm members constituting the working arm 7 of the present invention, and the working attachment 8 is attached to the tip portion of the arm 6. However, some of the various working attachments 8 as described above are attached to the tip portion of the boom 5. In this case, the working arm 7 does not include the arm 6. Moreover, the working arm 7 includes at least the boom 5 pivotally supported to be vertically pivotable on the machine body. However, when other arm members constituting the working arm 7 are provided in addition to the boom 5, the arm member is not limited to the arm 6, and various shapes or multiple arm members may be used.

[0022] Next, the oil supply / discharge of the boom cylinder 14 is explained using a schematic hydraulic circuit diagram in Fig. 2. In this case, reference numeral 15 represents a hydraulic pump serving as a hydraulic supply source for the boom cylinder 14, reference numeral 16 represents a pilot pump serving as a supply source for a pilot pressure, reference numeral 17 represents an oil tank, and reference numeral 18 represents a control valve for controlling the oil supply / discharge of the boom cylinder 14. As the hydraulic circuit of the hydraulic excavator 1, in addition to the boom cylinder 14, control circuits for other hydraulic actuators (the arm cylinder 10, the bucket cylinder 11, a swing motor (not shown) for swinging the upper swing body 3, or a travel motor (not shown)) and a circuit for controlling the discharge flow rate of the hydraulic pump are provided. However, illustration and description thereof are omitted.

[0023] The control valve (corresponding to a control valve of the present invention) 18 is a pilot-operated three-position spool valve having expansion-side and contraction-side pilot ports 18a and 18b. In a state where no pilot pressure is input to both pilot ports 18a and 18b, the control valve 18 is in a neutral position N, where no oil is supplied to or discharged from the boom cylinder 14. However, the control valve 18 is switched to an expansion-side position X when the pilot pressure is input to the expansion-side pilot port 18a. The oil supplied from the hydraulic pump 15 is supplied to the head-side oil chamber 14a of the boom cylinder 14 via an expansion-side supply port 18c, and the oil discharged from a rod-side oil chamber 14b is discharged into an oil tank 17 via an expansion-side drain port 18d.On the other hand, the control valve 18 is switched to a contraction-side position Y when the control pressure is input to the contraction-side control port 18b. The oil supplied from the hydraulic pump 15 is supplied to the rod-side oil chamber 14b of the boom cylinder 14 via a contraction-side supply port 18e, and the oil discharged from the head-side oil chamber 14a is discharged into the oil tank 17 via a contraction-side drain port 18f (which corresponds to a discharge port of the present invention). Then, the opening areas of the supply and discharge ports 18c and 18d on the expansion side and the supply and discharge ports 18e and 18f on the contraction side are controlled to increase or decrease them by a movement stroke of a spool that moves in response to the control pressures input to the supply and discharge ports 18a and 18b on the expansion and contraction sides.

[0024] In addition, Fig. 2, reference numerals 19 and 20 represent expansion-side and contraction-side electromagnetic proportional valves. The expansion-side and contraction-side electromagnetic proportional valves 19 and 20 respectively output the control pressures to the expansion-side and contraction-side control ports 18a and 18b of the control valve 18 based on a control signal output from a control unit 21 (described later). Then, the movement stroke of the spool of the control valve 18 is increased or decreased in response to an increase or decrease in the control pressures output from the expansion and contraction side electromagnetic proportional valves 19 and 20, and the opening areas of the supply and discharge ports 18c and 18d on the expansion side and the supply and discharge ports 18e and 18f on the contraction side are controlled to increase or decrease.

[0025] Here, when lowering the boom 5 in the air (when lowering the boom 5 in a state where the work attachment 8 is not on the ground), the weight of the front working part 4 (working arm 7 or work attachment 8) acts as the contraction force of the boom cylinder 14. Therefore, the pressure in the head-side oil chamber 14a of the boom cylinder 14 is sufficiently higher than the pressure in the rod-side oil chamber 14b. Therefore, the lowering speed of the boom 5 is controlled by controlling the discharge flow rate from the head-side oil chamber 14a of the boom cylinder (meter-out control).

[0026] On the other hand, the control unit (corresponding to the control means of the present invention) 21 controls the control valves for various hydraulic actuators and controls the discharge flow rate of the hydraulic pump 15 based on an operation of operating tools for various hydraulic actuators. In the control performed by the control unit 21, a part related to the lowering control of the boom 5 will be explained with reference to a control block diagram in Fig. 3. The boom operation detection means 23 for detecting an operation direction and an operation amount of a boom operation tool 23a (corresponding to an operation tool of the present invention) operated to vertically move the monitoring device 22 and the boom 5 is connected to an input side of the control unit 21, and the contraction-side electromagnetic proportional valve 20 is connected to an output side of the control unit 21. The control unit 21 is provided with each unit such as an attachment arm component determination unit 25, a work attachment weight calculation unit 26, a holding pressure mapping unit 27, a grouping unit 28, a holding pressure estimated value setting part 29, a target flow rate setting part 30, an opening area calculation unit 32, and a valve control unit 33.

[0027] The monitoring device 22 corresponds to the information input means of the present invention and is arranged in a cab 3a, which in the present embodiment is mounted on the upper swing body 3. The monitoring device 22 has a screen (not shown) for displaying information about various interchangeable work attachments 8 and operating elements (not shown) such as a keyboard or a touch panel, and stores information about the weight of various work attachments 8. Then, the monitoring device 22 is operated by an operator so that weight information about the attached work attachment 8 is input to the control unit 21. For example, work tools T1 to Tn and couplers C1 to Cn of the interchangeable work attachment 8 are displayed on the screen of the monitoring device 22.A work tool T and a coupler C (when the coupler is used) of the attached work attachment 8 are selected from the work tools T1 to Tn and the couplers C1 to Cn by the operating means. In this way, the weights Wt and Wc of the attached work tool T and the attached coupler C are input to the control unit 21. In this case, with respect to a specific work tool to which a heavy load is applied when carrying a heavy object, not only information about the weight of the work tool itself but also information about a load weight corresponding to the work tool (e.g., 1 / 2 of the maximum estimated load weight) is stored in the monitoring device 22. A configuration is adopted in which the weight obtained by adding the load weight to the weight of the work tool itself is output to the control unit 21 as the weight Wt of the work tool.

[0028] In addition, the monitoring device 22 is configured so that the operating device can select information about whether the work attachment 8 is attached to any arm link of the boom 5 and the arm 6, and the information about the arm link of the attachment is input to the control unit 21.

[0029] In the present embodiment, the monitoring device 22 is configured to store the information about the weights of the various work attachments 8. However, a configuration may be adopted in which the information is stored in the control unit 21 so that the monitoring device 22 performs only a selection operation. Even in this case, the information regarding the weight of the attached work attachment 8 is input to the control unit 21 based on an operation of the monitoring device 22.

[0030] Next, the lowering control of the boom 5 executed by the controller 21 will be explained with reference to Fig. 3. The controller 21 forwards the information output by the monitoring device 22 to the weight calculation unit for the work tool 25 and the weight calculation unit for the work attachment 26.

[0031] The attachment arm component determination unit 25 determines whether the work attachment 8 is attached to one of the boom 5 and the arm 6 based on the information input from the monitoring device 22, and outputs the determination result to the holding pressure map unit 27.

[0032] In addition, the work attachment weight calculation unit 26 calculates the weight W of the work attachment 8 based on the information input from the monitoring device 22. The weight W of the work attachment 8 is calculated by adding the weight Wt of the work tool T selected by the monitoring device 22 and the weight Wc of the coupler C (W=Wt+Wc). Then, the calculated weight W of the work attachment 8 is output to the holding pressure map unit 27.

[0033] The holding pressure map unit 27 is provided in advance with a map 35 indicating a relationship between the weight of the attachable work attachment 8 and the holding force of the head-side oil chamber 14a of the boom cylinder 14. In the map 35, a boom mounting map 35a when the work attachment 8 is attached to the end portion of the boom 5 and an arm mounting map 35b when the work attachment 8 is attached to the end portion of the arm 6 are individually provided. One of the boom mounting map 35a and the arm mounting map 35b is selected based on the determination result of the attachment arm component determination unit 25.

[0034] Then, the holding pressure map unit 27 uses the selected boom mounting map 35a or the selected arm mounting map 35b to obtain a holding force map value Pm corresponding to the weight W of the work attachment 8 calculated by the work attachment weight calculation unit 26. Then, the holding pressure map value Pm is output to the grouping unit 28.

[0035] Here, map 35 (boom mounting map 35a and arm mounting map 35b) shows the relationship between the weight W of the work attachment 8 and the holding pressure P of the oil chamber 14a on the head side of the boom cylinder in a linear relationship. The following describes a method for constructing map 35 using the arm mounting map 35b as an example when the interchangeable work attachment 8 is attached to the front part of the arm 6.

[0036] Fig. 1 shows the hydraulic excavator 1 when the following configuration is adopted. The work attachment 8 (bucket) is attached to the tip of the arm 6 via a tool support shaft 8a, and a posture of the work arm 7 (boom 5 and arm 6) is a maximum reach posture in which an axial height of the support shaft 8a corresponds to the axial height of a boom support shaft 5a (located on the same horizontal line H), and the axis of the attachment support shaft 8a is located at a position farthest from the axis of the boom support shaft 5a. The maximum reach posture is a posture in which a moment M around the boom support shaft 5a due to the weight of the front work part 4 is maximized. The moment M generated due to the weight of the front work part 4 at the maximum reach is obtained by the following formula (1). M=(W×L×g)+∑(Wi×Li×g)

[0037] In formula (1) and formulas (3) and (4), W is the weight of the working attachment 8 and L is a horizontal distance from an axial position of the boom support shaft 5a to a center of gravity position of the working attachment 8 at the maximum reach. Wi (i=1, 2, 3,... x) is the weight of each of the elements A1, A2, A3,... Ax (in the front working part 4, shown in Fig. 1, the boom 5, the arm cylinder 10, the arm 6, the bucket cylinder 11, a first link 12 and a second link 13) other than the working attachment 8 and forming the front working part 4, Li (i = 1, 2, 3, ... x) is a horizontal distance from the axial position of the boom support shaft 5a in the maximum reach position to the center of gravity position of each of the links A1, A2, A3, ... Ax, except for the working attachment 8 in the maximum reach position, and g is the acceleration due to gravity Fig. 1 shows the horizontal distances L, L1, L2, L3, L4, L5 and L6 from the axial position of the boom support shaft 5a to the axial positions of the work attachment 8, the boom 5, the arm cylinder 10, the arm 6, the bucket cylinder 11, the first link 12 and the second link 13.

[0038] On the other hand, the moment M around the boom support shaft 5a generated due to the holding pressure P of the head-side oil chamber 14a of the boom cylinder 14 is obtained by the formula (2). M=P×S×R

[0039] In formula (2) and formulas (3) and (4), P is the holding pressure of the head-side oil chamber 14a of the boom cylinder 14, S is a head-side pressure-receiving area of ​​a piston of the boom cylinder 14, and R is a lever arm. The lever arm R is the length of a vertical line from the axis of the boom support shaft 5a to a line of action (a straight line connecting the head-side support shaft 14c and the rod-side support shaft 14d of the boom cylinder 14) of the boom cylinder 14.

[0040] Then, based on a balance formula between the moment M around the boom support shaft 5a generated due to the weight of the front working part 4 and the moment M around the boom support shaft 5a generated due to the holding pressure P of the head-side oil chamber 14a of the boom cylinder 14, the holding pressure P of the head-side oil chamber 14a of the boom cylinder 14 at the maximum boom position of the front working part 4 is expressed by the formula (3). P={(W×L×g) / (S×R)}+{∑(Wi×Li×g) / (S×R)}

[0041] Then, "Σ(Wi×Li×g) / (S×R)" in formula (3) is an element other than the work attachment 8 and is a constant value ({Σ (Wi×Li×g) / (S×R)}=b: constant) regardless of the attached work attachment 8. In addition, if the horizontal distance L from the axial position of the support shaft of the boom 5a to the position of the center of gravity of the work attachment 8 is considered to be constant, even if the work attachment 8 is replaced, "(Lxg) / (SxR)" in formula (3) is also a constant value ({ (Lxg) / (SxR)}=a : constant). Therefore, formula (3) can be expressed as formula (4). P=(a×W)+b

[0042] Then, “a” and “b” in formula (4) are calculated and obtained based on known data or measurement data of each member constituting the front working part 4 and the boom cylinder 14. In this way, the arm mounting map 35b (see Fig. 4(A)) to show a relationship between the weight W of the work attachment 8 and the holding pressure P of the oil chamber 14a on the boom cylinder head side in a linear relationship.

[0043] In addition, when the work attachment 8 is attached to the front part of the boom 5, the values ​​of “a” and “b” in formula (4) are different. However, the boom mounting card 35a (see Fig. 4(B)) to indicate a relationship between the weight W of the work attachment 8 and the holding pressure P of the oil chamber 14a on the head side of the boom cylinder in a linear relationship. In this case, the attachment support shaft 8a is provided in the tip portion of the boom 5, and the maximum reach position is a position where the axial height of the attachment support shaft 8a is the same height as the axial height of the boom support shaft 5a (on the same horizontal line), and the axis of the attachment support shaft 8a is located at the position farthest from the axis of the boom support shaft 5a.

[0044] Then, as described above, the map 35 (boom mounting map 35a or arm mounting map 35b) is used to obtain the holding force map value Pm corresponding to the weight W of the attached work attachment 8 in the holding force map holding pressure map unit 27, and the holding force map value Pm is output to the grouping unit 28. In the grouping unit 28, the holding pressure map value Pm is grouped into a plurality of groups (three groups of first, second, and third groups G1, G2, and G3 in the present embodiment) according to a size of the holding pressure map value Pm. In this case, the threshold setting part 28a sets the same number of holding pressure threshold values ​​Pt (in the present embodiment, first, second, and third holding pressure threshold values ​​Pt1, Pt2, and Pt3 (Pt1≤Pt2≤Pt3)) as the number of groups, and the map value Pm of the holding pressure is grouped using the holding pressure threshold values.In the present embodiment, the holding pressure map value Pm is grouped into the first group G1 when the holding pressure map value Pm is equal to or less than the first holding pressure threshold value Pt1 (Pm≤Pt1). When the holding pressure map value Pm exceeds the first holding pressure threshold value Pt1 and is equal to or less than the second holding pressure threshold value Pt2 (Pt1 <Pm≤Pt2), wird der Haltedruck-Kartenwert Pm in die zweite Gruppe G2 gruppiert. Wenn der Wert des Haltedruckkennfelds Pm den zweiten Haltedruck-Schwellenwert Pt2 überschreitet und gleich dem dritten Haltedruck-Schwellenwert Pt3 oder kleiner als dieser ist (Pt2<Pm≤Pt3), wird der Wert des Haltedruckkennfelds Pm in die dritte Gruppe G3 gruppiert. Die Haltedruck-Schwellenwerte können entsprechend einer Größe oder Spezifikationen des Hydraulikbaggers 1 beispielsweise durch Verwendung externer Eingabemittel wie der Überwachungsvorrichtung 22 entsprechend geändert werden.Then, the grouping unit 28 outputs a grouping result, that is, whether the holding pressure map value Pm belongs to any of the first, second, and third groups, to the holding pressure estimation value setting part 29.

[0045] Here shows Fig. 5 each shows a result example in which various types and sizes of interchangeable work tools T1 to T25 (a bucket, a hammer, a compactor, a swing bucket, a clamshell bucket, a thumb bucket, grapple, and breaker) are mounted on the tip part of the arm 6 or the boom 5 without a coupler or via couplers C1 to C9, which can be combined with the work tools T1 to T25. In each case, the card 35 (boom mounting card 35a or arm mounting card 35b) is used to obtain the value Pm of the holding pressure card corresponding to the weight W of the work attachment 8 (work tool T and coupler C), and the value Pm of the holding pressure card is grouped (first, second, and third groups G1, G2, and G3).

[0046] On the other hand, when the group to which the holding force map value Pm belongs is input from the grouping unit 28, the holding pressure estimated value setting part 29 sets a holding force representative value set in advance for each group as the holding force estimated value P corresponding to the attached work attachment 8, and outputs the holding force estimated value P to the opening area calculation unit 32. In the present embodiment, the holding pressure representative value of each group is set to the maximum holding pressure map value Pm of the group, that is, the first group G1 is set to the first holding pressure threshold value Pt1, the second group G2 is set to the second holding pressure threshold value Pt2, and the third group G3 is set to the third holding pressure threshold value Pt3.The first, second and third holding pressure threshold values ​​Pt1, Pt2 and Pt3 respectively become the estimated holding pressure value P of the working attachment 8 belonging to the first, second and third groups G1, G2 and G3.

[0047] On the other hand, as described above, the boom operation detecting means 23 for detecting the operation of the boom operating tool 23a is connected to the input side of the control unit 21. However, an operation signal output from the boom operation detecting means 23 is input to the target flow rate setting part 30 of the control unit 21. When the operation signal on the boom lowering side is input from the boom operation detecting means 23, the target flow rate setting part 30 sets a target discharge flow rate Qt from the head-side oil chamber 14a of the boom cylinder 14 in accordance with the operation amount of the boom operating tool 23a to realize the boom lowering speed corresponding to the operation amount of the boom operating tool 23a. Then, the target discharge flow rate Qt is output to the opening area calculating unit 32.

[0048] Based on the estimated value P for the holding pressure inputted from the holding pressure estimated value setting part 29 and the desired discharge flow rate Qt inputted from the target flow rate setting part 30, the opening area calculation unit 32 uses the formula (6) derived from the formula (5) of the opening shown below and calculates the opening area of ​​the discharge port 18f on the contraction side of the control valve 18. Q=C×A×√(ΔP / ρ) A=(√ρ / C)×(Qt / √P)

[0049] In formula (5), Q is the flow rate of the nozzle, A is the orifice area of ​​the nozzle, ΔP is the differential pressure of the nozzle, C is a factor and ρ is the density of the liquid.

[0050] Furthermore, in formula (6), A is the opening area of ​​the discharge port 18f on the contraction side of the control valve 18, Qt is the target discharge flow rate set by the target flow rate setting part 30, P is the estimated holding pressure set by the holding pressure estimated value setting part 29, C is a flow coefficient, and ρ is the fluid density. In formula (6), the pressure (tank pressure) on the downstream side of the discharge port 18f on the throat side is regarded as "0 (zero)". Furthermore, a value of "√ρ / C" in formula (6) is regarded as a constant. The value of "√ρ / C" is set by a constant setting part 32a that uses external input means such as the monitor 22 and inputs it to the opening area calculation unit 32.

[0051] Then, the opening area of ​​the contraction-side outlet port 18f of the control valve 18, which is calculated using the formula (6), is output to the valve control unit 33.

[0052] Based on the opening area of ​​the contraction-side exhaust port 18f input from the opening area calculation unit 32, the valve control unit 33 obtains a spool movement stroke of the control valve 18 corresponding to the opening area. An input control pressure to the contraction-side control port 18b for moving a spool to the stroke is further obtained, and a current command value to the contraction-side electromagnetic proportional valve 20 for outputting the control pressure is further obtained. In this way, the current command value is output as a control signal to the contraction-side electromagnetic proportional valve 20. In this way, the contraction-side exhaust port 18f of the control valve 18 is controlled to have the opening area calculated by the opening area calculation unit 32.Then, since the opening area of ​​the contraction-side discharge port 18f of the control valve 18 is controlled in this way, the discharge flow rate from the head-side oil chamber 14a of the boom cylinder 14 can be controlled to correspond to the target discharge flow rate Qt set according to the operation of the boom operating tool 23a.

[0053] In the above-described embodiment, the hydraulic excavator 1 includes the working arm 7 having at least the boom 5 pivotally supported to be vertically pivotable on the upper swing body (machine body), the interchangeable work attachment 8 attached to the tip portion of the working arm 7, the boom cylinder 14 that allows the boom 5 to swing vertically by supplying oil to the head-side oil chamber 14a and contracting by discharging oil from the rod-side oil chamber 14b, and the control valve (control valve) 18 having the contraction-side discharge port (outlet port) 18f for controlling the discharge flow rate from the head-side oil chamber 14a of the boom cylinder 14, the control unit (control means) 21 for controlling the operation of the control valve 18, and the boom operating tool 23a that is operated to move the boom 5 vertically.Furthermore, the hydraulic excavator 1 is provided with the monitoring device (information input means) 22 for inputting information regarding the weight of the attached work tool 8 into the control unit 21. Then, the control unit 21 includes the map 35 indicating the relationship between the weight of the interchangeable work attachment 8 and the holding pressure of the oil chamber 14a on the head side of the boom cylinder. The control unit 21 obtains the estimated value of the holding pressure corresponding to the weight of the attached work attachment 8 based on the map 35.Based on the estimated value of the holding pressure, the control unit 21 controls the opening area of ​​the contraction-side discharge port 18f of the control valve 18 so that the discharge flow rate from the oil chamber 14a on the boom cylinder side corresponds to the target discharge flow rate set according to the operation amount of the boom operating tool 23a when the boom 5 is lowered.

[0054] In this way, in the embodiment of the present invention, the opening area of ​​the contraction-side discharge port 18f of the control valve 18 when lowering the boom 5 is controlled based on the estimated value of the holding pressure corresponding to the weight of the work attachment 8. In this way, even if the weight of the work attachment 8 changes due to replacement of the work attachment 8, the opening area can be controlled so that the discharge flow rate from the boom cylinder 14 is adjusted to that corresponding to the operation amount of the boom operation tool 23a, that is, so that the boom 5 can be lowered at the lowering speed corresponding to the operation amount of the boom operation tool 23a.In this case, however, the estimated value of the holding pressure is a fixed value obtained according to the weight of the attached work attachment 8 based on the map 35 provided in the control unit 21. Therefore, as in a case where the discharge flow rate is controlled by using a pressure detection value of the oil chamber 14a on the boom cylinder head side, which is frequently input from the pressure sensor as the holding pressure, a stable discharge flow rate can be controlled without the problem of unstable control after the opening area of ​​the discharge port 18f on the contraction side is irregularly changed in response to the pressure detection value. As a result, even when the work attachment 8 is replaced, the boom 5 can be lowered in a stable state at a lowering speed corresponding to the operation amount of the boom operation tool 23a.Therefore, this configuration can significantly improve usability.

[0055] Furthermore, in this configuration, when the control unit 21 obtains the estimated value of the holding pressure corresponding to the weight of the attached work attachment 8 based on the map 35, the control unit 21 groups the holding pressure map value of the boom head-side oil chamber 14a into the plurality of groups (three groups of the first, second, and third groups G1, G2, and G3 in the present embodiment) according to the size of the holding pressure map value, sets the representative value (first, second, and third holding pressure threshold values ​​Pt1, Pt2, and Pt3 in the present embodiment) of the holding pressure in advance for each group, and sets the representative value of the holding pressure of the group to which the holding pressure map value corresponding to the weight of the attached work attachment 8 belongs as the estimated holding pressure value corresponding to the weight of the attached work attachment 8.In this way, the holding pressure map value is grouped, and the representative value of the holding pressure of each group is set as the estimated holding pressure value used to control the discharge flow rate. This allows for more stable control of the boom lowering, and this configuration is ideal for tuning.

[0056] In addition, the map 35 shows the relationship between the weight of the work attachment 8 and the holding pressure of the oil chamber 14a on the head side of the boom cylinder in a linear relationship based on the moment about the support shaft (boom support shaft 5a) that pivotally supports the boom 5 on the machine body. Because the map 35 indicating the linear relationship is used in this way, the holding pressure values ​​corresponding to the weights of the various work attachments 8 can be easily determined.

[0057] Furthermore, in this configuration, the weight of the working attachment 8 includes the weight of the coupler used to attach the working attachment 8 to the tip portion of the working arm 7. In this way, even when the coupler is used, the estimated value of the holding pressure is obtained in consideration of the weight of the coupler, so that a correct estimated value of the holding pressure can be obtained.

[0058] Additionally, in the present embodiment, the work arm 7 includes the boom 5 and the arm 6 pivotally supported to be pivotable in the tip portion of the boom 5. On the other hand, the work attachment 8 attached to the tip portion of the boom 5 and the work attachment 8 attached to the tip portion of the arm 6 are provided as a work tool. Then, in the map 35 indicating the relationship between the weight of the interchangeable work attachment 8 and the holding pressure, the map (boom mounting map 35a) when the work attachment 8 is attached to the tip portion of the boom 5 and the map (arm mounting map 35b) when the work attachment is attached to the tip portion of the arm 6 are individually provided. In this way, the map 35 is individually provided in accordance with the work arm molding member (boom 5 or arm 6) to which the work attachment 8 is attached.Therefore, even if the working arm forming element to which the working attachment 8 is attached is the boom 5 or the arm 6, any suitable estimate of the holding pressure can be obtained.

[0059] In fact, the present embodiment is not limited to the above-described embodiment. For example, when the estimated value of the holding pressure corresponding to the weight of the attached work attachment is obtained based on the map, the work attachments are divided into several groups according to the size of the weight of the work attachment, and the representative value of the holding pressure is set in advance for each group. The map is used to obtain the representative value of the holding pressure of the group to which the attached work attachment belongs. In this way, a configuration can be adopted in which the representative value of the holding pressure is set as the estimated value of the holding pressure according to the weight of the attached work attachment.Since the work attachments are grouped in this way and the representative value of the holding pressure is set as the estimated value of the holding pressure, as in a case of the embodiment described above, the lowering of the boom can be controlled more stably, and this configuration is excellent for tuning.

[0060] In addition, in the above-described embodiment, when the opening area calculation unit 32 of the control unit 21 calculates the opening area of ​​the contraction-side discharge port (outlet port) 18f, the opening area is calculated using Formula (6) as described above. However, the opening area can be controlled more accurately by adding a correction value obtained in view of a pressure loss of the control valve 18 or a hydraulic line to this calculation.

[0061] Furthermore, in the embodiment described above, the map indicating the relationship between the weight of the work attachment and the holding pressure of the oil chamber on the head side of the boom is created under the assumption that the work arm is at the maximum reach. The reason for this is as follows. It is assumed that the holding pressure is the highest at the maximum reach, and control is performed under the assumption that the holding pressure is the highest. In this way, the boom lowering speed can be reliably prevented from being faster than the expected speed. However, in some cases, depending on the work contents performed by the work machine, it is conceivable that the holding pressure is higher. Therefore, to cope with this case, the correction value can be added to the map.

[0062] Furthermore, the present invention is not limited to the hydraulic excavator and can be applied to boom lowering control systems for various types of work machines in which the interchangeable work attachment is attached to the tip portion of the work arm including the boom. Industrial applicability

[0063] This invention is available for use in the hydraulic control system of a working machine such as a hydraulic excavator. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP-A-2003-106304

[0004] JP-A-2010-78035

[0004]

Claims

[1] A boom lowering control system in a work machine, comprising: a work arm including at least one boom pivotally mounted to pivot vertically on a machine body; an interchangeable work attachment mounted on a tip portion of the work arm; a boom cylinder that causes the boom to swing vertically by expanding through oil supply to a head-side oil chamber and contracts by oil discharge from the head-side oil chamber; a control valve having an outlet port for controlling a discharge flow rate from a head-side oil chamber of the boom cylinder; control means for controlling an operation of the control valve; and a An operating tool operated to move the boom vertically, the boom lowering control system comprising: Information input means for inputting information regarding a weight of the attached work attachment into the control means, wherein the control means includes a map indicating a relationship between the weight of the interchangeable work attachment and a holding pressure of the oil chamber on the boom cylinder head side, and obtains an estimated value for the holding pressure corresponding to the weight of the attached work attachment based on the map, and Based on the estimated value of the holding pressure, the control means controls an outlet opening area of ​​the control valve so that the discharge flow rate from the oil chamber on the boom cylinder head side becomes a target discharge flow rate set in accordance with an operation amount of the operation tool when the boom is lowered. [2] A boom lowering control system in a working machine according to claim 1, wherein, when the estimated value of the holding pressure corresponding to the weight of the attached work attachment is obtained based on the map, the control means groups a holding pressure map value of the oil chamber on the boom cylinder head side into a plurality of groups according to a size of the holding pressure map value to set a representative value of the holding pressure in advance for each group, and sets the representative value of the holding pressure of a group to which the holding pressure map value corresponding to the weight of the attached work attachment belongs as the estimated value of the holding pressure corresponding to the weight of the attached work attachment. [3] A boom lowering control system in a working machine according to claim 1, wherein, when the estimated value of the holding pressure corresponding to the weight of the attached work attachment is obtained based on the map, the control means sets a representative value of the holding pressure in advance for each group by grouping the work attachments into a plurality of groups according to a size of the weight of the work attachment, and sets the representative value of the holding pressure of a group to which the attached work attachment belongs as the estimated value of the holding pressure corresponding to the weight of the attached work attachment. [4] A boom lowering control system in a work machine according to any one of claims 1 to 3, wherein the map uses a linear relationship to indicate a relationship between the weight of the work attachment and the holding pressure of the oil chamber on the head side of the boom cylinder based on a moment about a support shaft for swingably supporting the boom on the machine body. [5] A boom lowering control system in a work machine according to claim 1, wherein the weight of the working attachment includes the weight of a coupler used to attach the working attachment to the tip portion of the working arm. [6] A boom lowering control system in a working machine according to claim 1, wherein the working arm comprises the boom and a stick pivotally mounted in a tip section of the boom, a working attachment attached to the tip section of the boom and a working attachment attached to the tip section of the stick are provided as the working attachment and the card when the work attachment is attached to the tip portion of the boom and the card when the work attachment is attached to the tip portion of the arm are provided separately.

Images