JP2023157145A - Boom lowering control system in work machine - Google Patents

Abstract

To perform a control for lowering a boom at a descending speed according to an operation tool operation amount in a stable condition even if a work attachment is replaced in a work machine in which a replaceable work attachment is attached to a tip of a work arm including a boom.SOLUTION: There is provided a monitor device 22 which inputs information regarding a weight of an attached work attachment 8 into a controller 21. The controller 21 is provided with a map 35 which shows a relationship between a weight of a replaceable work attachment 8 and a holding pressure of a boom cylinder head side oil chamber 14a. The controller 21 calculates a holding pressure estimation value according to the weight of the attached work attachment 8 based on the map 35, and controls an opening area of a contraction side discharge opening 18f of a control valve 18 based on the holding pressure estimation value.SELECTED DRAWING: Figure 3

Description

The present invention relates to the technical field of boom lowering control systems for working machines such as hydraulic excavators.

Some work machines, such as hydraulic excavators, are equipped with a boom that is pivotally supported on the main body of the machine so that it can freely swing up and down, and a work arm that is made up of a stick that is supported so that it can swing freely at the tip of the boom. Work attachments such as buckets, breakers, and crushers are attached to the tip of the arm so that they can be exchanged, and the vertical movement of the boom is extended by supplying oil to the oil chamber on the head side, allowing oil to be discharged from the oil chamber on the head side. There is one that is configured to do this by the telescopic operation of a boom cylinder that retracts. In such work machines, the weight of the work arm and work attachment acts as a force to lower the boom, so the pressure in the head side oil chamber of the boom cylinder is high, so the lowering speed of the boom cannot be controlled. This is normally performed by controlling the discharge flow rate from the boom cylinder head side oil chamber (meter-out control). In this case, for example, a control valve having a meter-out opening is provided in the discharge oil path from the boom cylinder head side oil chamber, and the meter-out opening area of the control valve is controlled to increase or decrease according to the operation amount of the boom operating tool. In this way, the boom lowering speed is controlled in accordance with the amount of operation of the operating tool.
However, as mentioned above, when controlling the descending speed of the boom by controlling the discharge flow rate from the boom cylinder head side oil chamber, the discharge flow rate from the head side oil chamber is determined not only by the opening area of the meter-out opening of the control valve, but also by controlling the discharge flow rate from the boom cylinder head side oil chamber. The pressure in the boom cylinder head side oil chamber increases or decreases depending on the pressure in the boom cylinder head side oil chamber, and the pressure in the boom cylinder head side oil chamber changes greatly depending on the weight of the work attachment that acts as a force for lowering the boom. Therefore, even if the opening area of the meter-out opening is the same, that is, the amount of operation of the boom operating tool is the same, the lowering speed of the boom will change depending on the weight of the attached work attachment, and the lowering speed of the boom will change. There is a problem that accurate control is not possible and operability is poor.
Conventionally, there has been a technology that has made it possible to maintain the boom lowering speed according to the operating amount of the operating tool even if the work attachment is replaced. For example, a control valve (meter-out control valve), a flow rate detection means for detecting the flow rate passing through the control valve, and a pressure sensor for detecting the holding pressure acting on the boom cylinder by an external force, and based on the detected holding pressure and flow rate. There are techniques that control the opening area of a control valve so that pressure opposing the holding pressure is generated on the inlet side of the control valve (see, for example, Patent Document 1), and a technique that controls the opening area of the control valve so that pressure that opposes the holding pressure is generated on the inlet side of the control valve. An electromagnetic proportional pressure reducing valve is provided in the regeneration circuit that supplies discharged oil from the chamber to the rod side oil chamber, and the opening degree of the electromagnetic proportional pressure reducing valve is set in advance with the pressure in the head side oil chamber detected by a pressure sensor. There is a known technology (for example, see Patent Document 2) in which control is performed based on the differential pressure between the target pressure value and the target pressure value of the head side oil chamber.

Japanese Patent Application Publication No. 2003-106304 Japanese Patent Application Publication No. 2010-78035

However, in both of Patent Documents 1 and 2, the opening area of the meter-out control valve and the opening degree of the electromagnetic proportional pressure reducing valve are determined based on the pressure of the boom cylinder head side oil chamber that is input from a pressure sensor at any time. It is configured to control. However, the pressure input from the pressure sensor at any time is dynamic pressure, and depending on the usage conditions of the work attachment, unstable and unpredictable pressure values may be input. There is a problem in that the control valve and the electromagnetic proportional pressure reducing valve move irregularly and cannot perform stable control, and this problem is to be solved by the present invention.

The present invention was created with the aim of solving these problems in view of the above-mentioned circumstances. A work arm that includes a work arm, a replaceable work attachment that is attached to the tip of the work arm, and expands when oil is supplied to the head side oil chamber and contracts when oil is discharged from the head side oil chamber to swing the boom up and down. A boom cylinder that is operated to move the boom, a control valve having a meter-out opening that controls the discharge flow rate from the head side oil chamber of the boom cylinder, a control means that controls the operation of the control valve, and a control valve that is operated to move the boom up and down. A working machine is provided with an information input means for inputting information regarding the weight of the attached work attachment into the control means, and the control means inputs information regarding the weight of the replaceable work attachment and the boom cylinder head side. Equipped with a map showing the relationship with the holding pressure of the oil chamber, based on this map, the estimated value of the holding pressure corresponding to the weight of the attached work attachment is calculated, and the pressure from the oil chamber on the boom cylinder head side when the boom is lowered is calculated. A boom lowering control system for a work machine, characterized in that a meter-out opening area of a control valve is controlled based on the estimated holding pressure value in order to make the discharge flow rate a target discharge flow rate set according to the operation amount of the operating tool. be.
In the invention of claim 2, in claim 1, the control means calculates the map value of the holding pressure of the oil chamber on the boom cylinder head side in calculating the estimated holding pressure value corresponding to the weight of the attached work attachment based on the map. are divided into a plurality of groups according to the size of the holding pressure map value, a representative value of holding pressure is set in advance for each group, and the holding pressure map value corresponding to the weight of the attached work attachment is set in advance. A boom lowering control system for a working machine is characterized in that a holding pressure representative value of a group to which it belongs is set as an estimated holding pressure value corresponding to the weight of an attached work attachment.
The invention of claim 3 is the invention according to claim 1, in which the control means adjusts the work attachment according to the weight of the work attachment when determining the estimated holding pressure value corresponding to the weight of the work attachment attached based on the map. Accordingly, the holding pressure is divided into multiple groups according to the weight of the attached work attachment, and the representative value of the holding pressure is set in advance for each group. This is a boom lowering control system for a working machine characterized by using an estimated holding pressure value.
The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the map calculates the weight of the work attachment and the boom cylinder head based on the moment around the support shaft that swingably supports the boom on the fuselage body. A boom lowering control system for a working machine is characterized in that the relationship with the holding pressure of a side oil chamber is expressed as a linear relationship.
The invention of claim 5 provides the boom lowering control in a working machine according to claim 1, wherein the weight of the work attachment includes the weight of a coupler used for attaching the work attachment to the tip of the work arm. It is a system.
The invention of claim 6 is based on claim 1, wherein the work arm includes a boom and a stick pivotably supported at the tip of the boom, and the work attachment is attached to the tip of the boom. There are two types: one that is attached to the tip of the stick, and one map that is attached to the tip of the boom, and another map that is attached to the tip of the stick. A boom lowering control system for a working machine is characterized by the following.

According to the invention of claim 1, even if the work attachment is replaced, the control for lowering the boom at a lowering speed corresponding to the operation amount of the boom operating tool can be performed in a stable state, and the operation is improved. It can greatly contribute to improving sexual performance.
By adopting the inventions of claims 2 and 3, more stable boom lowering control can be performed and excellent tuning is achieved.
According to the invention of claim 4, holding pressure map values corresponding to the weights of various work attachments can be easily obtained.
According to the fifth aspect of the invention, the estimated value of the holding pressure is determined by taking into account the weight of the coupler, so that an appropriate estimated value of the holding pressure can be obtained.
According to the invention of claim 6, it is possible to obtain appropriate holding pressure estimation values regardless of whether the work arm component to which the work attachment is attached is a boom or a stick.

FIG. 2 is a schematic side view of the hydraulic excavator in a maximum reach position. It is a hydraulic circuit diagram of a boot cylinder. It is a control block diagram of a boom lowering control system. (A) is a map for stick mount, and (B) is a diagram showing a map for boom mount. FIG. 3 is a table showing the grouping of work attachments.

Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a schematic side view of a hydraulic excavator 1, which is an example of a working machine of the present invention. The upper revolving body 3 (corresponding to the main body of the present invention), which is mounted on the upper revolving body 3, and the front working machine 4 mounted on the upper revolving body 3, further includes a base end portion of the front working machine 4. A boom 5 is supported on the upper revolving body 3 via a boom support shaft 5a so as to be swingable up and down, and a stick 6 is supported at the tip of the boom 5 via a stick support shaft 6a so as to be swingable back and forth. A work arm 7 consisting of a work arm 7, a work attachment 8 movably attached to the tip of the stick 6 via an attachment support shaft 8a, a stick cylinder 10 that extends and contracts to swing the stick 6, and a work attachment 8 that swings the work attachment 8. It is composed of various members such as a bucket cylinder 11 that expands and contracts for movement, and first and second links 12 and 13 that connect the tip of the bucket cylinder 11 to the stick 6 and the work attachment 8, respectively.

Furthermore, 14 is a boom cylinder that extends and contracts to swing the boom 5 up and down, and the head side end of the boom cylinder 14 swings toward the front of the upper revolving structure 3 via the head side support shaft 14c. The rod side end portion is swingably supported at the longitudinally intermediate portion of the boom 5 via the rod side support shaft 14d, and the head side oil chamber 14a of the boom cylinder 14 (see FIG. (not shown) expands and raises the boom 5, and contracts when oil is discharged from the head side oil chamber 14a to lower the boom 5.

Here, in FIG. 1, a bucket is shown as the work attachment 8 attached to the tip of the work arm 7, but a breaker is attached to the tip of the work arm 7 depending on the work to be performed by the hydraulic excavator 1. Various work tools such as (hammer), compactor, tilt bucket, clamshell bucket, thumb bucket, grapple, and crusher (all not shown) can be attached interchangeably. Furthermore, when attaching these work tools to the tip of the work arm 7, there are cases where a coupler is not used as in the case of the bucket shown in FIG. A coupler that allows the work tool to be tilted or rotated with respect to the work arm may be used.Furthermore, when a coupler is used, the combination of the work tool and coupler can be selected as appropriate depending on the function of the coupler, etc. It looks like this. In this embodiment, when a coupler is used, the work tool and the coupler are used as the work attachment 8, and when the coupler is not used, the work tool is used as the work attachment 8.
1 shows a boom 5 and a stick 6 as arm members constituting the work arm 7 of the present invention, and a work attachment 8 is attached to the tip of the stick 6. Some of the work attachments 8 are attached to the tip of the boom 5, and in that case, the work arm 7 does not include the stick 6. Further, the work arm 7 includes at least a boom 5 that is pivotally supported on the main body of the machine so as to be able to freely swing up and down, but if there is another arm member constituting the work arm 7 in addition to the boom 5, the arm member is The present invention is not limited to the stick 6, and various shapes and numbers of arm members may be used.

Next, the oil supply and discharge control for the boom cylinder 14 will be explained based on the schematic hydraulic circuit diagram of FIG. 2. In FIG. A pilot pump serves as a supply source, 17 is an oil tank, and 18 is a control valve that controls oil supply and discharge to the boom cylinder 14. Note that the hydraulic circuit of the hydraulic excavator 1 includes other hydraulic actuators other than the boom cylinder 14 (the stick cylinder 10, the bucket cylinder 11, or a swing motor (not shown) for turning the upper revolving structure 3), a travel motor (not shown), etc. (not shown), a circuit for controlling the discharge flow rate of the hydraulic pump, etc., are also provided, but illustrations and explanations thereof will be omitted.

The control valve (corresponding to the control valve of the present invention) 18 is a pilot-operated three-position switching spool valve having expansion side and contraction side pilot ports 18a, 18b, and both pilot ports 18a, 18b have pilot ports 18a, 18b. When pressure is not input, the boom cylinder 14 is located at the neutral position N where no oil is supplied or discharged, but when pilot pressure is input to the extension side pilot port 18a, it is switched to the extension side position X. The oil supplied from the hydraulic pump 15 is supplied to the head-side oil chamber 14a of the boom cylinder 14 via the extension-side supply opening 18c, and the oil discharged from the rod-side oil chamber 14b is supplied to the extension-side discharge opening 18d. On the other hand, when pilot pressure is input to the reduction side pilot port 18b, the oil is switched to the reduction side position Y, and the oil supplied from the hydraulic pump 15 is passed through the reduction side supply opening 18e. The oil is supplied to the rod side oil chamber 14b of the boom cylinder 14, and the oil discharged from the head side oil chamber 14a is sent to the oil tank 17 via the contraction side discharge opening 18f (corresponding to the meter-out opening of the present invention). It is designed to flow to The opening areas of the expansion side supply and discharge openings 18c and 18d and the contraction side supply and discharge openings 18e and 18f are determined according to the pilot pressures input to the expansion and contraction side pilot ports 18a and 18b. The increase or decrease is controlled by the movement stroke of the moving spool.

Furthermore, in FIG. 2, reference numerals 19 and 20 indicate electromagnetic proportional valves on the expansion side and contraction side, and these electromagnetic proportional valves 19 and 20 on the expansion side and contraction side operate based on control signals output from a controller 21, which will be described later. , pilot pressures are output to the expansion side and contraction side pilot ports 18a and 18b of the control valve 18, respectively. The spool movement stroke of the control valve 18 increases or decreases by increasing or decreasing the pilot pressure output from the extension side and contraction side electromagnetic proportional valves 19 and 20, and the expansion side supply and discharge openings 18c and 18d are reduced. The opening areas of the side supply and discharge openings 18e and 18f are controlled to increase or decrease.

Here, when lowering the boom 5 in the air (when lowering the boom 5 with the work attachment 8 not in contact with the ground), the weight of the front work equipment 4 (work arm 7, work attachment 8, etc.) Since it acts as a force for contraction, 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 boom cylinder head side oil chamber 14a (meter-out control).

On the other hand, the controller 21 (corresponding to the control means of the present invention) controls the control valves for various hydraulic actuators, the discharge flow rate of the hydraulic pump 15, etc. based on the operation of the operating tools for the various hydraulic actuators. However, among the controls performed by the controller 21, the part related to the lowering control of the boom 5 will be explained based on the control block diagram of FIG. A boom operation detection means 23 for detecting the operation direction and operation amount of the operated boom operation tool 23a (corresponding to the operation tool of the present invention) is connected, and the reduction side electromagnetic proportional valve 20 is connected to the output side. In addition, the mounting arm member determination section 25, the work attachment weight calculation section 26, the holding pressure map section 27, the grouping section 28, the holding pressure estimated value setting section 29, the target discharge flow rate setting section 30, the opening area calculation section 32, Various parts such as a valve control part 33 are provided.

The monitor device 22 corresponds to the information input means of the present invention, and in this embodiment, it is disposed inside the cab 3a mounted on the upper revolving body 3, and is equipped with various replaceable work attachments. It has a display screen (not shown) for displaying information such as 8 and operating means (not shown) such as a keyboard and touch panel, and also stores information regarding the weight of various work attachments 8. Then, when the operator operates the monitor device 22, weight information of the attached work attachment 8 is input to the controller 21. For example, work tools T1 to Tn and couplers C1 to Cn of replaceable work attachments 8 are displayed on the display screen of the monitor device 22, and the work attachment 8 attached from among these work tools T1 to Tn and couplers C1 to Cn is displayed. By selecting the work tool T and coupler C (if a coupler is used) using the operating means, the weights Wt and Wc of the installed work tool T and coupler C are input to the controller 21. In this case, for a specific work tool that is subject to a heavy load, such as when carrying a heavy object, it is important to consider not only the weight of the work tool itself, but also the load weight corresponding to the work tool (for example, 1/2 of the maximum estimated load weight). Information is also stored in the monitor device 22, and the weight obtained by adding the load weight to the weight of the work tool itself is output to the controller 21 as the weight Wt of the work tool.
Further, the monitor device 22 is configured such that information as to which arm member of the boom 5 or the stick 6 the work attachment 8 is attached to can be selected using the operating means, and information on the attachment arm member is also sent to the controller 21. It is now entered.
In this embodiment, the information regarding the weight of various work attachments 8 is stored in the monitor device 22, but it is also possible to store this information in the controller 21 and use the monitor device 22 to perform only selection operations. It can also be done. Even in this case, information regarding the weight of the attached work attachment 8 is input to the controller 21 based on the operation of the monitor device 22.

Next, the lowering control of the boom 5 performed by the controller 21 will be explained based on FIG. 26.
The attachment arm member determination section 25 determines whether the work attachment 8 is attached to the boom 5 or the stick 6 based on information input from the monitor device 22, and uses the determination result as a holding pressure map section 27. Output to.
Further, the work attachment weight calculation unit 26 calculates the weight W of the work attachment 8 based on information input from the monitor 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 monitor 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 section 27.

The holding pressure map section 27 is previously provided with a map 35 showing the relationship between the weight of the attachable work attachment 8 and the holding pressure of the head side oil chamber 14a of the boom cylinder 14. The map 35 includes a boom mount map 35a when the work attachment 8 is attached to the tip of the boom 5, and a stick mount map 35b when the work attachment 8 is attached to the tip of the stick 6. Based on the determination result of the attachment arm member determining section 25, either the boom mount map 35a or the stick mount map 35b is selected.
Then, the holding pressure map section 27 calculates the holding pressure corresponding to the weight W of the work attachment 8 calculated by the work attachment weight calculation section 26 using the selected boom mount map 35a or stick mount map 35b. Find the map value Pm. Then, the holding pressure map value Pm is output to the grouping section 28.

Here, the maps 35 (boom mount map 35a, stick mount map 35b) express the relationship between the weight W of the work attachment 8 and the holding pressure P of the boom cylinder head side oil chamber 14a in a linear relationship. However, the method for creating the map 35 will be described below, taking as an example the stick mount map 35b in which the replaceable work attachment 8 is attached to the tip of the stick 6.
In FIG. 1, the work attachment 8 (bucket) is attached to the tip of the stick 6 via the attachment support shaft 8a, and the posture of the work arm 7 (boom 5 and stick 6) is adjusted to the axis of the attachment support shaft 8a. The maximum height at which the height is the same as the axial center height of the boom support shaft 5a (located on the same horizontal line H), and the axial center of the attachment support shaft 8a is at the farthest position from the axial center of the boom support shaft 5a. The hydraulic excavator 1 is shown in the reach position, and the maximum reach position is the position in which the moment M around the boom support shaft 5a due to the weight of the front work equipment 4 is maximum. The moment M due to the weight of the front working machine 4 is determined by the following equation (1).
M=(W×L×g)+Σ(Wi×Li×g)...(1)
In the above equation (1) and the following equations (3) and (4), W is the weight of the work attachment 8, and L is the horizontal distance from the axial center position of the boom support shaft 5a to the center of gravity position of the work attachment 8 in the maximum reach position. The distance, Wi (i=1, 2, 3, ... 4, the weight of the boom 5, stick cylinder 10, stick 6, bucket cylinder 11, first link 12, second link 13, etc.), and Li (i=1, 2, 3, . . . x) are the maximum reach The horizontal distance from the axial center position of the boom support shaft 5a in the posture to the center of gravity position of each member A1, A2, A3, . . . Ax other than the work attachment 8, g is the gravitational acceleration. In addition, in FIG. 1, the horizontal distance from the axial center position of the boom support shaft 5a to the axial center positions of the work attachment 8, boom 5, stick cylinder 10, stick 6, bucket cylinder 11, first link 12, and second link 13 is shown. L, L1, L2, L3, L4, L5, and L6 are shown.
On the other hand, the moment M around the boom support shaft 5a due to the holding pressure P of the head side oil chamber 14a of the boom cylinder 14 is determined by the following equation (2).
M=P×S×R...(2)
In the above formula (2) and the following formulas (3) and (4), P is the holding pressure of the head side oil chamber 14a of the boom cylinder 14, S is the head side pressure receiving area of the piston of the boom cylinder 14, and R is the moment arm The moment arm R has the length of a perpendicular line extending from the axis of the boom support shaft 5a to the line of action of the boom cylinder 14 (the straight line connecting the head side support shaft 14c and the rod side support shaft 14d of the boom cylinder 14). It is.
From the equation of balance between the moment M around the boom support shaft 5a due to the weight of the front work equipment 4 and the moment M around the boom support shaft 5a due to the holding pressure P of the head side oil chamber 14a of the boom cylinder 14, front work The holding pressure P of the head side oil chamber 14a of the boom cylinder 14 in the maximum reach attitude of the machine 4 is expressed by the following equation (3).
P={(W×L×g)/(S×R)}+{Σ(Wi×Li×g)/(S×R)} ...(3)
"Σ(Wi×Li×g)/(S×R)" in the above formula (3) is an element other than the work attachment 8 and is a constant value ({Σ (Wi×Li×g)/(S×R)}=b: constant), and furthermore, even if the work attachment 8 is replaced, the horizontal distance from the axial center position of the boom support shaft 5a to the center of gravity position of the work attachment 8 When distance L is considered constant, "(L x g)/(S x R)" in the above formula (3) is also a constant value ({(L x g)/(S x R)} = a : constant), so equation (3) can be expressed as equation (4) below.
P=(a×W)+b...(4)
By calculating "a" and "b" in the above formula (4) based on known data or measured data of each member constituting the front work machine 4 and the boom cylinder 14, the work attachment 8 A stick mount map 35b (see FIG. 4(A)) is created that expresses the relationship between the weight W and the holding pressure P of the boom cylinder head side oil chamber 14a in a linear relationship.
In addition, when the work attachment 8 is attached to the tip of the boom 5, the values of "a" and "b" in the above equation (4) are different, but the weight W of the work attachment 8 and the boom A boom map 35a (see FIG. 4(B)) is created that expresses the relationship with the holding pressure P of the cylinder head side oil chamber 14a in a linear relationship. In this case, the attachment support shaft 8a is provided at the tip of the boom 5, and the maximum reach posture is such that the axial center height of the attachment support shaft 8a is the same height as the axial center height of the boom support shaft 5a (on the same horizontal line). ), and the axial center of the attachment support shaft 8a is at the farthest position from the axial center of the boom support shaft 5a.

Then, as described above, using the map 35 (boom mount map 35a or stick mount map 35b), a map value of the holding pressure corresponding to the weight W of the work attachment 8 attached in the holding pressure map section 27 is obtained. Pm is obtained, and the holding pressure map value Pm is output to the grouping section 28, which divides the holding pressure map value Pm according to the magnitude of the holding pressure map value Pm. They are divided into a plurality of groups (in this embodiment, three groups: first, second, and third groups G1, G2, and G3). In this case, the threshold setting unit 28a sets the same number of holding pressure thresholds Pt as the number of groups (in this embodiment, first, second, and third holding pressure thresholds Pt1, Pt2, and Pt3 (Pt1≦Pt2≦Pt3). In this embodiment, when the holding pressure map value Pm is less than or equal to the first holding pressure threshold Pt1 (Pm≦Pt1), the holding pressure map value Pm is classified into the first group G1; When the pressure threshold Pt1 is exceeded and the second holding pressure threshold Pt2 or less (Pt1<Pm≦Pt2), it is set as the second group G2, and when the pressure exceeds the second holding pressure threshold Pt2 and is below the third holding pressure threshold Pt3 (Pt2<Pm ≦Pt3), it is set as the third group G3.The values of these holding pressure thresholds are changed as appropriate depending on the size and specifications of the hydraulic excavator 1, for example, using external input means such as the monitor device 22. Then, the grouping unit 28 outputs the grouping result, that is, to which group the holding pressure map value Pm belongs, the first, second, or third, to the holding pressure estimated value setting unit 29. do.

Here, FIG. 5 shows various types and sizes of work tools T1 to T25 (buckets, breakers (hammers), compactors, tilt buckets, clamshell buckets, thumb buckets, grapples, crushers, etc.) that can be replaced. In each case, the map 35 (boom mount map 35a or stick mount map 35b) is attached to the tip of the stick 6 or boom 5 without a coupler or via couplers C1 to C9 that can be combined with work tools T1 to T25. is used to find the holding pressure map value Pm corresponding to the weight W of the work attachment 8 (work tool T and coupler C), and divide the holding pressure map value Pm into groups (first, second, third groups G1, G2, G3) An example of the result is shown below.

On the other hand, when the group to which the holding pressure map value Pm belongs is input from the grouping unit 28, the holding pressure estimated value setting unit 29 sets the holding pressure representative value set in advance for each group to the work attachment 8. is set as the holding pressure estimated value P corresponding to , and outputs the holding pressure estimated value P to the opening area calculation section 32. In this embodiment, the holding pressure representative value of each group is the maximum holding pressure map value Pm of the group, that is, the first holding pressure threshold Pt1 for the first group G1, and the second holding pressure threshold Pt2 for the second group G2. , the third group G3 is set to the third holding pressure threshold Pt3, and these first, second, and third holding pressure thresholds Pt1, Pt2, and Pt3 are respectively set to the first, second, and third groups G1, This is the estimated holding pressure value P of the work attachments 8 belonging to G2 and G3.

On the other hand, as described above, the boom operation detection means 23 for detecting the operation of the boom operation tool 23a is connected to the input side of the controller 21, and the operation signal output from the boom operation detection means 23 is , is input to the target discharge flow rate setting section 30 of the controller 21. The target discharge flow rate setting unit 30 sets the boom operating tool to a boom lowering speed according to the operating amount of the boom operating tool 23a when a boom lowering operation signal is input from the boom operation detecting means 23. A target discharge flow rate Qt from the head side oil chamber 14a of the boom cylinder 14 is set according to the operation amount of the boom cylinder 23a. Then, the target discharge flow rate Qt is output to the opening area calculation section 32.

The opening area calculation section 32 calculates the orifice as shown below based on the estimated holding pressure P input from the estimated holding pressure setting section 29 and the target discharge flow rate Qt input from the target discharge flow rate setting section 30. Using equation (6) derived from equation (5), the opening area of the reduction side discharge opening 18f of the control valve 18 is calculated.
Q=C×A×√(ΔP/ρ)...(5)
A=(√ρ/C)×(Qt/√P)...(6)
In the above equation (5), Q is the flow rate passing through the orifice, A is the opening area of the orifice, ΔP is the differential pressure across the orifice, C is the flow coefficient, and ρ is the fluid density.
In addition, in (6) above, A is the opening area of the reduction side discharge opening 18f of the control valve 18, Qt is the target discharge flow rate set by the target discharge flow rate setting section 30, and P is the holding pressure estimated value setting section 29. The set holding pressure estimate, C is the flow coefficient, and ρ is the fluid density. In addition, in formula (6), the pressure (tank pressure) on the downstream side of the reduction side discharge opening 18f is regarded as "0 (zero)". Further, the value of "√ρ/C" in equation (6) is regarded as a constant, and the value of "√ρ/C" can be determined by the constant setting section 32a using external input means such as the monitor device 22. It is set and input to the aperture area calculation section 32.
Then, the opening area of the contraction side discharge opening 18f of the control valve 18 calculated using the above equation (6) is output to the valve control section 33.

Based on the opening area of the reduction-side discharge opening 18f inputted from the opening area calculation unit 32, the valve control unit 33 determines the spool movement stroke of the control valve 18 that corresponds to the opening area. Furthermore, the input pilot pressure to the reduction side pilot port 18b for moving the spool to the specified stroke is determined, the current command value to the reduction side electromagnetic proportional valve 20 for outputting the pilot pressure is determined, and the current The command value is output to the reduction side electromagnetic proportional valve 20 as a control signal. Thereby, the reduction side discharge opening 18f of the control valve 18 is controlled to have the opening area calculated by the opening area calculating section 32. By controlling the opening area of the contraction side discharge opening 18f of the control valve 18 in this way, the discharge flow rate from the head side oil chamber 14a of the boom cylinder 14 can be set in accordance with the operation of the boom operating tool 23a. This means that control can be performed to achieve the target discharge flow rate Qt.

In the embodiment configured as described above, the hydraulic excavator 1 includes a working arm 7 including at least a boom 5 that is pivotally supported on an upper revolving body (body body) so as to be vertically swingable, and a distal end portion of the working arm 7. a boom cylinder 14 that expands when oil is supplied to the head-side oil chamber 14a and contracts when oil is discharged from the head-side oil chamber 14b to swing the boom 5 up and down; A control valve (control valve) 18 having a reduction side discharge opening (meter-out opening) 18f that controls the discharge flow rate from the head side oil chamber 14a of the cylinder 14, and a controller (control valve) that controls the operation of the control valve 18. 21 and a boom operating tool 23a that is operated to move the boom 5 up and down, the hydraulic excavator 1 further inputs information regarding the weight of the work attachment 8 attached to the hydraulic excavator 1 to the controller 21. A monitor device (information input means) 22 is provided. The controller 21 is equipped with a map 35 showing the relationship between the weight of the replaceable work attachment 8 and the holding pressure of the boom cylinder head side oil chamber 14a, and the attached work attachment is determined based on the map 35. 8 is calculated, and the discharge flow rate from the boom cylinder head side oil chamber 14a when the boom 5 is lowered is set to a target discharge flow rate set according to the operation amount of the boom operating tool 23a. Preferably, the opening area of the reduction side discharge opening 18f of the control valve 18 is controlled based on the estimated holding pressure value.

In this embodiment of the present invention, the opening area of the contraction side discharge opening 18f of the control valve 18 when the boom 5 is lowered is controlled based on the estimated holding pressure corresponding to the weight of the work attachment 8. By doing so, even if the weight of the work attachment 8 changes due to replacement of the work attachment 8, the discharge flow rate from the boom cylinder 14 can be maintained at the target discharge flow rate set according to the operation amount of the boom operating tool 23a. In other words, the boom 5 can be controlled to be lowered at a lowering speed corresponding to the operation amount of the boom operation tool 23a. Since this is a fixed value determined according to the weight of the attached work attachment 8 based on As shown in the figure, there is no problem such as the opening area of the reduction side discharge opening 18f changing irregularly depending on the detected pressure value and the control becomes unstable, and stable discharge flow rate control can be performed. . As a result, even if the work attachment 8 is replaced, the boom 5 can be stably lowered at a lowering speed corresponding to the operation amount of the boom operating tool 23a, which can greatly contribute to improved operability.

Furthermore, in this device, the controller 21 calculates the estimated value of the holding pressure corresponding to the weight of the attached work attachment 8 based on the map 35 by using the map value of the holding pressure of the boom cylinder head side oil chamber 14a as the holding pressure. The map values are divided into multiple groups (first, second, and third groups G1, G2, and G3 in this embodiment) according to the magnitude of the map values, and the representative value of the holding pressure is determined for each group. (In this embodiment, the first, second, and third holding pressure thresholds Pt1, Pt2, and Pt3) are set in advance, and the holding pressure of the group to which the holding pressure map value corresponding to the weight of the attached work attachment 8 belongs is set in advance. The representative value is the estimated holding pressure value corresponding to the weight of the attached work attachment 8, but the holding pressure map values are divided into groups in this way, and the holding pressure representative value of each group is used as the holding pressure used for discharge flow rate control. By using the estimated value, more stable boom lowering control can be performed and it is also excellent for tuning.

Furthermore, the map 35 is based on the weight of the work attachment 8 and the holding pressure of the boom cylinder head side oil chamber 14a based on the moment around the support shaft (boom support shaft 5a) that swingably supports the boom 5 on the fuselage body. By using the map 35 expressed in such a linear relationship, holding pressure map values corresponding to the weights of various work attachments 8 can be easily obtained.

Furthermore, in this device, the weight of the work attachment 8 includes the weight of the coupler used to attach the work attachment 8 to the tip of the work arm 7. As a result, even when a coupler is used, the estimated value of the holding pressure is determined by taking the weight of the coupler into consideration, and an appropriate estimated value of the holding pressure can be obtained.

Further, in the present embodiment, the work arm 7 is composed of a boom 5 and a stick 6 that is swingably supported at the tip of the boom 5, while the work attachment 8 is constructed from the boom 5. The map 35 showing the relationship between the weight and holding pressure of the replaceable working attachment 8 shows that the working attachment 8 is attached to the tip of the boom 5. A map (boom mount map 35a) for when the stick 6 is attached to the tip of the stick 6 (boom mount map 35a) and a map (stick mount map 35b) for the case when it is attached to the tip of the stick 6 are provided separately. In this way, by providing the map 35 individually according to the work arm component (boom 5, stick 6) to which the work attachment 7 is attached, even if the work arm component to which the work attachment 8 is attached is the boom 5. Even with the stick 6, appropriate holding pressure estimation values can be obtained.

Note that this embodiment is, of course, not limited to the above-described embodiment. For example, when calculating the estimated holding pressure value corresponding to the weight of the work attachment attached based on the map, the work attachment is Attachments are divided into multiple groups according to their weight, and a representative value of holding pressure is set in advance for each group, and a map is used to determine the representative value of holding pressure for the group to which the attached work attachment belongs. It is also possible to use a configuration in which the holding pressure representative value is determined and the holding pressure representative value is used as the holding pressure estimated value corresponding to the weight of the attached work attachment. By grouping in this way and using the holding pressure representative value as the holding pressure estimated value, more stable boom lowering control can be performed and excellent tuning is possible, as in the case of the above embodiment.
Furthermore, in the above embodiment, when the opening area calculation unit 32 of the controller 21 calculates the opening area of the reduction side discharge opening (meter-out opening) 18f, the calculation is performed using equation (6) as described above. However, by adding a correction value that takes into account the pressure loss of the control valve 18 and hydraulic piping to this calculation, more accurate opening area control can be performed.
Furthermore, in the embodiment described above, the map showing the relationship between the weight of the work attachment and the holding pressure of the boom cylinder head side oil chamber is created assuming that the work arm is in the maximum reach position. This is because it is assumed that the holding pressure is highest at the maximum reach position, and by performing control assuming that the holding pressure is the highest, the boom lowering speed will be faster than the expected speed. However, it is thought that the holding pressure may become higher depending on the work performed by the work machine, and correction values may be added to the map in preparation for such cases. can.
Further, the present invention is not limited to hydraulic excavators, but can be implemented in boom lowering control systems of various working machines in which a replaceable work attachment is attached to the tip of a work arm including a boom.

INDUSTRIAL APPLICATION This invention can be utilized for the boom lowering control system when the work attachment is replaced in working machines, such as a hydraulic excavator.

5 Boom 5a Boom support shaft 6 Stick 7 Work arm 8 Work attachment 14 Boom cylinder 14a Head side oil chamber 18 Control valve 18f Reduction side discharge opening 21 Controller 22 Monitor device 23a Boom operating tool 27 Holding pressure map section 28 Grouping section 30 Target discharge flow rate setting section 32 Opening area calculation section 35 Map 35a Map for boom mount 35b Map for stick mount

Claims (6)

A work arm that includes at least a boom that is pivotably supported on the main body of the machine so as to be able to swing vertically, an exchangeable work attachment that is attached to the tip of the work arm, and a head side that extends by supplying oil to the head side oil chamber. A boom cylinder that is contracted by oil discharge from an oil chamber to cause the boom to swing up and down, a control valve having a meter-out opening that controls the discharge flow rate from the head side oil chamber of the boom cylinder, and operation of the control valve. In a work machine comprising a control means for controlling a boom and an operating tool operated to move the boom up and down, an information input means is provided for inputting information regarding the weight of an attached work attachment to the control means. The means includes a map showing the relationship between the weight of the replaceable work attachment and the holding pressure of the boom cylinder head side oil chamber, and calculates the estimated holding pressure value corresponding to the weight of the installed work attachment based on the map. At the same time, the meter-out opening area of the control valve is determined based on the estimated holding pressure value in order to make the discharge flow rate from the boom cylinder head side oil chamber when the boom is lowered to the target discharge flow rate set according to the operation amount of the operating tool. A boom lowering control system for a working machine, characterized in that: In claim 1, the control means calculates the estimated holding pressure value corresponding to the weight of the attached working attachment based on the map, by comparing the map value of the holding pressure of the boom cylinder head side oil chamber with the holding pressure map value. The groups are divided into multiple groups according to the size, and the representative value of the holding pressure is set in advance for each group, and 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 belongs. A boom lowering control system for a working machine, characterized in that the holding pressure is estimated to correspond to the weight of an attached work attachment. In claim 1, the control means groups the work attachments into a plurality of groups according to the size of the weight of the work attachment when determining the estimated holding pressure value corresponding to the weight of the work attachment attached based on the map. The representative value of the holding pressure is set in advance for each group, and the representative value of the holding pressure of the group to which the attached work attachment belongs is set as the estimated value of the holding pressure corresponding to the weight of the attached work attachment. A boom lowering control system for a working machine characterized by: In any one of claims 1 to 3, the map calculates the weight of the work attachment and the holding pressure of the oil chamber on the boom cylinder head side based on the moment about the support shaft that swingably supports the boom on the fuselage body. A boom lowering control system for a working machine, characterized in that the relationship is expressed as a linear relationship. 2. The boom lowering control system for a working 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 of the working arm. In claim 1, the work arm includes a boom and a stick that is swingably supported at the tip of the boom, and the work attachment is attached to the tip of the boom and the stick is attached to the tip of the stick. A working machine characterized in that a map is provided separately for the case where the work attachment is attached to the tip of the boom and the map when it is attached to the tip of the stick. boom lowering control system.

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