Control system for construction machinery

Abstract

In construction machinery equipped with a stick, this invention aims to avoid excessive or insufficient pump flow rate to the stick cylinder due to factors such as the stick's orientation and the weight of the load, while also reducing costs and simplifying control. [Solution] The control device 17 includes a first map 26 that sets the basic pump flow rate according to the amount of operation of the stick control tool, and a second map 27 that sets a correction value to correct the basic pump flow rate set in the first map 26 according to the differential pressure between the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9. The control device 17 is configured to correct the basic pump flow rate set in the first map 26 using the correction value set in the second map 27, and to output a control signal to the variable capacity means 11a of the hydraulic pump 11 to achieve the corrected pump flow rate.

Description

Technical Field

[0001] The present invention relates to the technical field of control systems for construction machinery such as hydraulic excavators.

Background Art

[0002] Among construction machinery, there is a type such as a hydraulic excavator, in which a front working unit mounted on the machine body is composed of a boom, a stick, a bucket, etc., and these boom, stick, and bucket are driven based on the telescopic operation of hydraulic cylinders for the boom, stick, and bucket. In the machine body of such construction machinery equipped with hydraulic cylinders, a variable displacement type hydraulic pump serving as a pressure oil supply source for the hydraulic cylinders is mounted, and in the cab, operating tools for operating each hydraulic cylinder are provided. Furthermore, in recent years, operation detection means for detecting the operation amount of the operating tool for the hydraulic cylinder has been provided, and a control device for outputting a control signal to the capacity variable means of the hydraulic pump based on an input signal from the operation detection means has been provided to promote the electronic control of the hydraulic pump. In this case, generally, the pump flow rate is controlled to increase or decrease in accordance with the increase or decrease in the operation amount of the operating tool. However, the operating speed of the hydraulic cylinder changes depending on the posture of the working unit and the weight of the load loaded on the working unit even when the operation amount of the operating tool is the same. For example, when the weight of the load is heavy, compared with the case when it is light, the operating speed of the hydraulic cylinder in the direction of lowering the load becomes faster, and the operating speed of the hydraulic cylinder in the direction of raising the load becomes slower. Therefore, if the pump flow rate control is based only on the operation amount of the operating tool, there is a risk that the pump flow rate supplied to the hydraulic cylinder becomes excessive and enters a boost state, or the pump flow rate becomes insufficient and enters a vacuum state, resulting in the problem that efficient control cannot be performed. Therefore, conventionally, a technique has been known in which a position detector is provided to detect the rotation angle of each front member (boom, stick, bucket) constituting the work section, and a pressure detector is provided to detect the pressure in the head-side oil chamber and the rod-side oil chamber of the hydraulic cylinder. Based on the input signals from these detectors, the gravity component of the direction vector of the front member movement is calculated, the maximum pump flow rate is calculated, the pump flow rate increase rate is calculated, the equivalent mass of the front member is calculated, a correction coefficient is calculated, and the corrected pump flow rate increase rate is calculated. Based on these calculation results, the pump flow rate is controlled so that the pump flow rate is controlled not only in accordance with the amount of operation of the operating tool, but also in accordance with the direction vector of the movement of the front member and the equivalent mass of the front member (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6707053 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the device described in Patent Document 1 requires a position detector (rotation angle detector) to detect the relative position of the front member, in addition to the operating amount detector and pressure detector of the operating tool. Many construction machines do not have such a position detector, and installing a new position detector incurs costs and effort. Furthermore, it requires many complex calculations as described above (calculation of the gravity direction component of the direction vector of the front member's movement, calculation of the maximum pump flow rate, calculation of the pump flow rate increase rate, calculation of the equivalent mass of the front member, calculation of the correction coefficient, and calculation of the corrected pump flow rate increase rate), which complicates the control. This is the problem that the present invention aims to solve. [Means for solving the problem]

[0005] The present invention was created in view of the above circumstances and with the aim of solving these problems, and the invention of claim 1 is a construction machine comprising a boom supported on the machine body so as to be able to move up and down, and a stick supported at the tip of the boom so as to be able to swing, and the swing of the stick is configured to be performed based on the extension and retraction operation of a stick cylinder, and in providing a control system for controlling the pump flow rate of a variable capacity hydraulic pump which is the source of pressurized oil for the stick cylinder, the control system comprises operation detection means for detecting the operation of an operating tool for the stick for operating the stick cylinder, pressure detection means for detecting the differential pressure between the head side oil chamber and the rod side oil chamber of the stick cylinder, and these operation detection The control system for construction machinery is characterized by providing a control device that outputs a control signal to a variable-capacity means of a hydraulic pump based on input signals from an output means and a pressure detection means, the control device comprising a first map that sets a basic pump flow rate according to the amount of operation of a stick-type operating tool input from an operation detection means, and a second map that sets a correction value for correcting the basic pump flow rate set in the first map according to the differential pressure between the head-side oil chamber and the rod-side oil chamber input from a pressure detection means, the control device corrects the basic pump flow rate set in the first map using the correction value set in the second map, and outputs a control signal to the variable-capacity means of the hydraulic pump to achieve the corrected pump flow rate. The invention of claim 2 is a control system for a construction machine, characterized in that, in claim 1, the second map sets correction values ​​separately for the extension side and the retraction side of the stick cylinder. The invention of claim 3 is a control system for construction machinery, characterized in that, in claim 1, the correction value set by the second map is a numerical value of 0 or more and 1 or less that is multiplied by the basic pump flow rate, and the correction value is set to be 1 or close to 1 when the differential pressure between the head-side oil chamber and the rod-side oil chamber is small, and to approach 0 when the differential pressure is large. The invention of claim 4 is a control system for a construction machine, characterized in that, in claim 1, the control system includes a regeneration circuit that supplies discharged oil from the rod-side oil chamber of the stick cylinder to the head-side oil chamber, and the second map sets a correction value to reduce the pump flow rate by the amount of regeneration flow rate corresponding to the differential pressure between the rod-side oil chamber and the head-side oil chamber. The invention of claim 5 is a control system for construction machinery, characterized in that, in any one of claims 1 to 4, the second map is created based on data obtained by actually measuring the relationship between the differential pressure between the head-side oil chamber and the rod-side oil chamber of the stick cylinder and the operating speed of the stick cylinder. [Effects of the Invention]

[0006] By adopting the invention of claim 1, problems such as excessive or insufficient pump flow to the stick cylinder resulting in boost or vacuum states can be effectively avoided, enabling efficient pump flow control and contributing to improved operability. Moreover, it does not require expensive equipment such as position detectors to detect the stick's attitude, contributing to cost reduction, and also has the advantage of being easy to control. By adopting the invention of claim 2, efficient pump flow rate control can be performed using separate correction values ​​for the extension side and the contraction side, respectively. By adopting the invention of claim 3, the corrective pump flow rate can be made equivalent to the basic pump flow rate in the region of small differential pressure, which has little effect on the operating speed of the stick cylinder, while the corrective pump flow rate can be reduced in the region of large differential pressure, which is affected by horsepower control, thereby enabling more efficient pump flow rate control. By adopting the invention of claim 4, the pump flow rate for regeneration can be reduced, enabling more efficient pump flow rate control. By adopting the invention of claim 5, it is possible to create a highly accurate second map that corresponds to the actual device. [Brief explanation of the drawing]

[0007] [Figure 1] This is a side view of a hydraulic excavator. [Figure 2] This is a diagram of the hydraulic control circuit for a stick cylinder. [Figure 3] This figure shows the opening characteristics of the first and second regions at the extension-side operating position of the control valve for the stick. [Figure 4] This is a schematic diagram of measured data showing the relationship between the differential pressure in the head-side oil chamber and the rod-side oil chamber of a stick cylinder and the operating speed. [Figure 5] (A) is the first map, (B) is the second map, and (C) is a diagram showing an example of pump flow rate correction. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In Figure 1, 1 is a hydraulic excavator, which is an example of a construction machine of the present invention. The hydraulic excavator 1 is composed of various parts, including a crawler-type lower traveling body 2, an upper rotating body 3 that is rotatably supported on the lower traveling body 2, and a front working section 4 that is mounted on the upper rotating body 3. The front working section 4 is further composed of a boom 5 whose base end is supported on the upper rotating body 3 so as to be able to swing up and down, a stick 6 that is supported on the tip of the boom 5 so as to be able to swing back and forth, a bucket 7 that is rotatably attached to the tip of the stick 6, and boom cylinders 8, stick cylinders 9, bucket cylinders 10, etc., which extend and retract to cause the boom 5, stick 6, and bucket 7 to swing, respectively. In Figure 1, L is a vertical line passing through the pivot axis 6a of the stick 6. Furthermore, in the following explanation, the movement of the stick 6 in the direction that brings the tip of the stick 6 closer to the aircraft (upper rotating body 3) is referred to as stick in (movement towards the inward side), and the movement of the stick 6 in the direction that moves the tip of the stick 6 away from the aircraft is referred to as stick out (movement towards the outward side).

[0009] The stick cylinder 9 is configured to swing the stick 6 inward by extending due to the supply of pressurized oil to the head-side oil chamber 9a and the discharge of oil from the rod-side oil chamber 9b, while it swings the stick 6 outward by contracting due to the supply of pressurized oil to the rod-side oil chamber 9b and the discharge of oil from the head-side oil chamber 9a. The pressurized oil supply and discharge control for the stick cylinder 9 will be explained based on the hydraulic control circuit diagram shown in Figure 2. In Figure 2, 11 is a variable displacement hydraulic pump that serves as the pressurized oil supply source for the stick cylinder 9, 11a is a variable displacement means for the hydraulic pump 11, 12 is a pump oil passage to which the discharged oil from the hydraulic pump 11 is supplied, 13 is an oil tank, and 14 is a control valve for the stick that controls the oil supply and discharge for the stick cylinder 9.

[0010] The stick control valve 14 is a four-position spool valve equipped with extension and retraction pilot ports 14a and 14b. When no pilot pressure is input to either pilot port 14a or 14b, it is in a neutral position N, where it does not supply or discharge pressurized oil to or from the stick cylinder 9. However, when pilot pressure is input to the retraction pilot port 14b, it switches to the retraction operating position X, opening a supply valve passage 14c to supply discharged oil from the hydraulic pump 11 to the rod-side oil chamber 9b of the stick cylinder 9, and opening a discharge valve passage 14d to allow discharged oil from the head-side oil chamber 9a to flow to the oil tank 13. Furthermore, when pilot pressure is input to the extension-side pilot port 14a, the system switches to the extension-side operating position Y, which is provided with a first region Y1 and a second region Y2. In this case, the second region Y2 is set to a position where the spool's movement stroke from the neutral position N is greater than that of the first region Y1. When the system is in the first region Y1, the regeneration valve passage 14f, which supplies discharged oil from the rod-side oil chamber 9b of the stick cylinder 9 to the head-side oil chamber 9a via the check valve 14e, and the supply valve passage 14g, which supplies discharged oil from the hydraulic pump 11 to the head-side oil chamber 9a, are opened, and the discharge valve passage 14h, which discharges the discharged oil from the rod-side oil chamber 9b to the oil tank 13, is also opened. However, the discharge valve passage 14h in the first region Y1 is restricted and its opening area is set to be small (see Figure 3). Furthermore, when located in the second region Y2, the supply valve passage 14g that supplies discharged oil from the hydraulic pump 11 to the head-side oil chamber 9a is opened, and the discharge valve passage 14h that discharges oil from the rod-side oil chamber 9b to the oil tank 13 is opened. However, the opening area of ​​the supply valve passage 14g in the second region Y2 is set to be larger than the opening area of ​​the supply valve passage 14g in the first region Y1, and the opening area of ​​the discharge valve passage 14h in the second region Y2 is configured to open wide without being restricted like the discharge valve passage 14h in the first region Y1 (see Figure 3). In Figure 3, the regeneration valve passage 14f is also open in the second region Y2, but as will be described later, the second region Y2 is the region located when the head-side oil chamber 9a is at a higher pressure than the rod-side oil chamber 9b, so the regeneration valve passage 14f in the second region Y2 is closed by the check valve 14e. Here, the opening areas of the supply valve passage 14c and discharge valve passage 14d in the retracted operating position X are uniquely set according to the movement stroke of the spool displaced by the pilot pressure input to the retracted pilot port 14b. Furthermore, the opening areas of the regeneration valve passage 14f, supply valve passage 14g, and discharge valve passage 14h in the first region Y1 of the extension operating position Y, and the supply valve passage 14g and discharge valve passage 14h in the second region Y2 are uniquely set according to the movement stroke of the spool displaced by the pilot pressure input to the extension pilot port 14a. In addition, the opening characteristics of the supply valve passage and discharge valve passage are set according to meter-in control, which controls the operating speed by the supply flow rate to the stick cylinder 9, and meter-out control, which controls the operating speed by the discharge flow rate from the stick cylinder 9. In this embodiment, the regeneration valve passage 14f provided in the stick control valve 14 constitutes a regeneration circuit that supplies the discharged oil from the rod-side oil chamber to the head-side oil chamber according to the present invention.

[0011] Furthermore, in Figure 2, 15 is the extension-side solenoid valve and 16 is the retraction-side solenoid valve. These extension-side and retraction-side solenoid valves 15 and 16 output pilot pressure to the extension-side and retraction-side pilot ports 14a and 14b of the stick control valve 14 based on control signals from the control device 17, which will be described later. The spool of the stick control valve 14 is displaced by the pilot pressure output from these extension-side and retraction-side solenoid valves 15 and 16 to the extension-side operating position Y and the retraction-side operating position X as described above. In this case, the movement stroke of the spool is controlled to increase or decrease according to the increase or decrease in pilot pressure. The stick control valve 14 is set to be in the first region Y1 of the extension-side operating position Y if the pilot pressure output from the extension-side solenoid valve 15 is less than a predetermined pilot pressure Pp, and to be in the second region Y2 if it is equal to or greater than the predetermined pilot pressure Pp (see Figure 3).

[0012] Also, in FIG. 2, 18 is a bypass oil passage from the pump oil passage 12 to the oil tank 13, 19 is a bypass control valve for controlling the flow rate of the bypass oil passage 18, and 20 is a bypass solenoid valve that outputs pilot pressure to the bypass control valve 19 based on a control signal from the control device 17.

[0013] Furthermore, in FIG. 2, 21 is an operation detection means for detecting the operation (operation direction and operation amount) of a stick operation tool (not shown, such as an operation lever), 22 is a pump pressure sensor for detecting the discharge pressure (pump pressure) of the hydraulic pump 11, 23 is a head side pressure sensor for detecting the pressure of the head side oil chamber 9a of the stick cylinder 9, and 24 is a rod side pressure sensor for detecting the pressure of the rod side oil chamber 9b of the stick cylinder 9 (these head side and rod side pressure sensors 23 and 24 correspond to the pressure detection means for detecting the differential pressure of the present invention). The detection signals of these operation detection means 21, pressure sensors 22, 23, and 24 are input to the control device 17.

[0014] And the control device 17 outputs control signals to the extension side and reduction side solenoid valves 15 and 16, the bypass solenoid proportional valve, and the capacity variable means 11a of the hydraulic pump 11 based on these input signals, thereby controlling the stick control half 14 and performing pump flow rate control to be described later.

[0015] First, regarding the control of the stick control valve 14 by the control device 17, when the control device 17 receives a stick-out operation signal from the operation detection means 21, it outputs a control signal for pilot pressure output to the retraction-side solenoid valve 16. In this case, the control device 17 outputs a control signal so that the pilot increases or decreases in accordance with the increase or decrease in the amount of operation of the stick operating tool. As a result, pilot pressure is input to the retraction-side pilot port 14b of the stick control valve 14, and the stick control valve 14 switches to the retraction-side operating position X. As a result, when a stick-out operation is performed, the discharge oil from the hydraulic pump 11 is supplied to the rod-side oil chamber 9b of the stick cylinder 9 via the stick control valve 14 in the retraction-side operating position X, while the discharge oil from the head-side oil chamber 9a flows to the oil tank 13, causing the stick cylinder 9 to retract.

[0016] On the other hand, when the control device 17 receives a stick-in operation signal from the operation detection means 21, it determines whether regeneration from the rod-side oil chamber 9b to the head-side oil chamber 9a is possible based on the pressures in the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9, which are input from the head-side and rod-side pressure sensors 23 and 24. In this case, if the pressure Pr in the rod-side oil chamber 9b is higher than the pressure Ph in the head-side oil chamber 9a (Pr>Ph), it is determined that regeneration is possible, and if the pressure Ph in the head-side oil chamber 9a is greater than or equal to the pressure Pr in the rod-side oil chamber 9b (Ph≧Pr), it is determined that regeneration is not possible.

[0017] When an operation signal of the stick-in is input from the operation detection means 21, the control device 17 outputs a control signal for pilot pressure output to the extension side solenoid valve 15, whereby pilot pressure is input to the extension side pilot port 14a of the stick control valve 14 and it switches to the extension side operating position Y. In this case, if it is determined that regeneration from the rod side oil chamber 9b to the head side oil chamber 9a is possible (the pressure Pr in the rod side oil chamber 9b is higher than the pressure Ph in the head side oil chamber 9a (Pr > Ph)), for the extension side solenoid valve 15, a control signal is output so as to output a pilot pressure less than the predetermined pilot pressure Pp, that is, a pilot pressure for positioning the stick control valve 14 in the first region Y1 (a pilot pressure at which the spool displacement amount becomes the first region Y1). In this case, the control device 17 controls the output pilot pressure from the extension side solenoid valve 15 so that the movement stroke of the spool increases or decreases according to an increase or decrease in the operation amount of the stick operating tool within a range less than the predetermined pilot pressure Pp (within a range where the stick control valve 14 is positioned in the first region Y1). As a result, the stick control valve 14 is positioned in the first region Y1, and the regenerated oil from the rod side oil chamber 9b and the discharged oil of the hydraulic pump 11 are supplied to the head side oil chamber 9a, while the discharged oil from the rod side oil chamber 9b flows to the oil tank 13 and the stick cylinder 9 extends. In this case, since the discharge valve passage 14h in the first region Y1 is in a throttled state, the amount of regenerated oil can be increased. In response to this, when a stick-in operation signal is input from the operation detection means 21, if it is determined that regeneration from the rod-side oil chamber 9b to the head-side oil chamber 9a is impossible (the pressure Ph in the head-side oil chamber 9a is greater than or equal to the pressure Pr in the rod-side oil chamber 9b (Ph≧Pr)), the control device 17 outputs a control signal to the extension-side solenoid valve 15 to output a pilot pressure equal to or greater than the predetermined pilot pressure Pp, that is, a pilot pressure that causes the stick control valve 14 to be positioned in the second region Y2 (a pilot pressure at which the spool displacement amount becomes the second region Y2). In this case, the control device 17 controls the output pilot pressure from the extension-side solenoid valve 15 so that the spool displacement amount increases or decreases in accordance with the increase or decrease in the amount of operation of the stick operating tool, within the range of the predetermined pilot pressure Pp or greater (the range in which the stick control valve 14 is positioned in the second region Y2). As a result, the control valve 14 for the stick is located in the second region Y2, and the discharge oil from the hydraulic pump 11 is supplied to the head-side oil chamber 9a, while the discharge oil from the rod-side oil chamber 9b flows to the oil tank 13, causing the stick cylinder 9 to extend. In this case, the opening area of ​​the discharge valve passage 14h in the second region Y2 is larger than that of the discharge valve passage 14h in the first region Y1, so the pressure in the rod-side oil chamber 9b can be quickly reduced, thus preventing the stick cylinder 9 from operating slowly due to high pressure in the rod-side oil chamber 9b.

[0018] Next, the operation of the in-side (stick cylinder 9 extension side) and out-side (stick in-cylinder 9 retraction side) of the stick 6, and the differential pressure between the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9 during operations of the front work section 4 such as excavation and loading operations, will be explained separately for the following cases (1) to (4). For convenience, the differential pressure here will be defined as the pressure obtained by subtracting the pressure Pr of the rod-side oil chamber 9b from the pressure Ph of the head-side oil chamber 9a (Ph-Pr). This differential pressure (Ph-Pr) will be a "positive (+)" value ((Ph-Pr)>0) when the pressure in the head-side oil chamber 9a is higher than that in the rod-side oil chamber 9b, and a "negative (-)" value ((Ph-Pr)<0) when the pressure in the rod-side oil chamber 9b is higher than that in the head-side oil chamber 9a. Furthermore, the differential pressure between the head-side oil chamber and the rod-side oil chamber in this invention includes not only the pressure obtained by subtracting the pressure Pr of the rod-side oil chamber 9b from the pressure Ph of the head-side oil chamber 9a, but also the pressure obtained by subtracting the pressure Ph of the head-side oil chamber 9a from the pressure Pr of the rod-side oil chamber 9b.

[0019] (1) Stick-in (extension of stick cylinder 9) when differential pressure (Ph-Pr) > 0 (head-side oil chamber 9a is at a higher pressure than rod-side oil chamber 9b) In this case, the control valve 14 for the stick is located in the second region Y2 of the extension-side operating position Y, and the stick cylinder 9 extends while pressurized oil is supplied to the head-side oil chamber 9a, pushing the cylinder piston from the head-side oil chamber 9a side (a state in which meter-in control is dominant). This applies during drilling or during aerial operations where the stick 6 is stuck in on the side of the vertical line L (see (1) in Figure 1). During drilling, pressurized oil is supplied to the head-side oil chamber 9a against the drilling resistance, so the differential pressure (Ph-Pr) is relatively large, and the greater the differential pressure (Ph-Pr), the lower the pump flow rate becomes due to horsepower control of the hydraulic pump 11, and the slower the operating speed of the stick cylinder 9. Furthermore, the horsepower control described above is a control that reduces the pump flow rate in accordance with the increase in pump pressure so that the power of the hydraulic pump 11 does not exceed the power supplied from the power source (engine). The hydraulic pump 11 in this embodiment is equipped with a horsepower control mechanism (not shown) for performing horsepower control.

[0020] (2) Stick-in (extension of stick cylinder 9) when differential pressure (Ph-Pr) < 0 (rod-side oil chamber 9b is at a higher pressure than head-side oil chamber 9a) In this case, the stick control valve 14 is located in the first region Y1 of the extension-side operating position Y, and the stick cylinder 9 extends with the cylinder piston being pushed towards the rod oil chamber 9b by external forces (such as the weight of the stick 6 and bucket 7, and the weight of the load in the bucket 7) (a state in which meter-out control is dominant). This mainly applies when the stick 6 is operated in the air from the maximum reach (the position furthest out) to the vertical line L (see (2) in Figure 1), where the weight of the stick 6 and the load act in the direction that lowers the stick 6 (inward). Regeneration from the rod-side oil chamber 9b to the head-side oil chamber 9a is effective, and the amount supplied to the head-side oil chamber 9a is the sum of the pump supply flow rate and the regeneration flow rate. During regeneration from the rod-side oil chamber 9b to the head-side oil chamber 9a, pressure is generated on both the head side and the rod side (for example, the head-side oil chamber 9a experiences approximately half the pressure of the rod-side oil chamber 9b), so the absolute value of the differential pressure |Ph-Pr| is relatively small.

[0021] (3) Stick-out (retraction of stick cylinder 9) when differential pressure (Ph-Pr) < 0 (rod-side oil chamber 9b is at a higher pressure than head-side oil chamber 9a) In this case, the stick control valve 14 is in the contraction operating position X, and the stick cylinder 9 contracts while supplying pressurized oil to the rod-side oil chamber 9b, pushing the cylinder piston from the rod-side oil chamber 9b side (a state where meter-in control is dominant). This mainly applies when the stick 6 is moved outward from the vertical line L to the maximum reach side in the air (see (3) in Figure 1), and most stick-out operations fall under this category. Pressurized oil is supplied to the rod-side oil chamber 9b to raise the stick 6 against external forces (the weight of the stick 6 and bucket 7, the weight of the load, etc.), and the higher the absolute value of the differential pressure |Ph-Pr| due to horsepower control of the hydraulic pump 11, the lower the pump flow rate and the slower the operating speed of the stick cylinder 9. However, due to the difference in piston pressure receiving area between the head side and the rod side of the stick cylinder 9, the speed of stick-out is faster than stick-in even with the same pump supply flow rate.

[0022] (4) Stick-out (retraction of stick cylinder 9) when differential pressure (Ph-Pr) > 0 (head-side oil chamber 9a is at a higher pressure than rod-side oil chamber 9b) In this case, the stick control valve 14 is in the contraction-side operating position X, and the stick cylinder 9 contracts while the cylinder piston is pushed toward the head-side oil chamber 9a by external forces (such as the weight of the stick 6 and bucket 7, and the weight of the load in bucket 7). This applies to aerial operations where the stick 6 is stuck out on the side of the vertical line L (see (4) in Figure 1), where the weight of the stick 6 and the load act in the direction of lowering the stick 6 (outward). However, this condition rarely occurs during actual operation, and the proportion of time it takes up in actual operating time is very small.

[0023] Here, when the relationship between the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 is plotted based on actual measurement data obtained by operating the stick control tool under various conditions in the actual hydraulic excavator 1 to perform stick-in and stick-out, it is distributed within the area enclosed by the solid line in the schematic diagram shown in Figure 4. In Figure 4, the differential pressure (Ph-Pr) is the pressure obtained by subtracting the pressure Pr in the rod-side oil chamber 9b from the pressure Ph in the head-side oil chamber 9a, as described above. It is a "positive (+)" value when the pressure in the head-side oil chamber 9a is higher than that in the rod-side oil chamber 9b, and a "negative (-)" value when the pressure in the rod-side oil chamber 9b is higher than that in the head-side oil chamber 9a. The operating speed of the stick cylinder 9 is represented by a "positive (+)" value on the cylinder extension side and a "negative (-)" value on the cylinder retraction side.

[0024] The first quadrant of Figure 4 shows the relationship between the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 when, in the case of (1) described above, that is, when the head-side oil chamber 9a is under higher pressure than the rod-side oil chamber 9b and the stick cylinder is stuck in (both the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 are positive (+)). In this case, as described above, the differential pressure (Ph-Pr) increases due to excavation resistance, etc., and the larger the differential pressure (Ph-Pr), the lower the pump flow rate due to the horsepower control of the hydraulic pump 11, and the slower the operating speed of the stick cylinder 9 becomes.

[0025] Furthermore, the second quadrant of Figure 4 shows the relationship between the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 when, as described in (2) above, the rod-side oil chamber 9b is at a higher pressure than the head-side oil chamber 9a and the stick cylinder is stuck in (the differential pressure (Ph-Pr) is "negative (-)" and the operating speed of the stick cylinder 9 is "positive (+)"). In this case, as described above, regeneration from the rod-side oil chamber 9b to the head-side oil chamber 9a is effective, and when the regeneration flow rate is added to the pump supply flow rate, the operating speed of the stick cylinder 9 increases, but the absolute value of the differential pressure |Ph-Pr| is relatively small. Note that in the second quadrant of Figure 4, the relationship between the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 when only the pump supply flow rate is used and the regeneration flow rate is not added is shown by a dotted line.

[0026] Furthermore, the third quadrant of Figure 4 shows the relationship between the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 when, as described in (3) above, the rod-side oil chamber 9b is under higher pressure than the head-side oil chamber 9a and sticks out (both the differential pressure (Ph-Pr) and the operating speed of the stick cylinder 9 are negative (-)). In this case, as described above, the higher the absolute value of the differential pressure |Ph-Pr| due to the horsepower control of the hydraulic pump 11, the lower the pump flow rate and the slower the operating speed of the stick cylinder 9. Furthermore, the fourth quadrant in Figure 4 represents the case described in (4) above, that is, the region where stick-out occurs when the head-side oil chamber 9a is at a higher pressure than the rod-side oil chamber 9b (the differential pressure (Ph-Pr) is "positive (+)" and the operating speed of the stick cylinder 9 is "negative (-)"). However, as mentioned above, this is a region of operation that rarely occurs in actual operation, and even if pump flow rate control using the correction value described later is set in this region, the control will rarely be effective. Therefore, in this embodiment, in order to simplify the control, pump flow rate control using the correction value is not performed in this region, and data measurement is omitted.

[0027] Next, the pump flow rate control performed by the control device 17 will be explained. The control device 17 is equipped with a pump flow rate control unit 25, which controls the pump flow rate of the hydraulic pump 11. The pump flow rate control unit 25 is equipped with a first map 26, a second map 27, and a corrected pump flow rate calculation unit 28, which will be described later. The first map 26 and the second map 27 are provided separately for the extension side and the contraction side (stick in and stick out) of the stick cylinder 9, respectively, but here we will explain using the stick in case as an example.

[0028] The first map 26 is a map showing the relationship between the amount of operation of the stick-type control device and the pump flow rate, and as shown in Figure 5(A), it is set so that the pump flow rate increases as the amount of operation of the control device increases. When the pump flow rate control unit 25 receives an operation signal for the stick-type control device from the operation detection means 21, it uses the first map 26 to determine the pump flow rate corresponding to the amount of operation and sets the pump flow rate determined by the first map 26 as the basic pump flow rate.

[0029] On the other hand, the second map 27 is a map for determining a correction value Cp to correct the basic pump flow rate obtained in the first map 26 according to the differential pressure (Ph-Pr) between the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9. As shown in Figure 5(B), the second map 27 shows the relationship between the differential pressure (Ph-Pr) and the correction value Cp. The correction value Cp is a value between "0 (zero)" and "1" (0≦Cp≦1) that is multiplied by the basic pump flow rate, and in this embodiment, it is set based on the measured data of the relationship between the operating speed of the stick cylinder 9 and the differential pressure (Ph-Pr) shown in Figure 4. The pump flow rate control unit 25 then determines the differential pressure (Ph-Pr) between the head-side oil chamber 9a and the rod-side oil chamber 9b based on the pressure values ​​input from the head-side pressure sensor 23 and the rod-side pressure sensor 24, and uses the second map 27 to determine a correction value Cp corresponding to the differential pressure (Ph-Pr).

[0030] Furthermore, the corrected pump flow rate calculation unit 28 calculates the corrected pump flow rate (corrected pump flow rate) by multiplying the basic pump flow rate set using the first map 26 by the correction value Cp obtained using the second map 27. Then, it outputs a control signal to the variable capacity means 11a of the hydraulic pump 11 so that the pump flow rate becomes the corrected pump flow rate. As a result, the pump flow rate of the hydraulic pump 11 is controlled to become the corrected pump flow rate corrected according to the differential pressure (Ph-Pr). Figure 5(C) shows, for example, the corrected pump flow rate when the correction value Cp is "0.75".

[0031] Here, the setting of the correction value Cp in the case of stick-in will be explained in detail based on Figure 5(B). For example, in the case of (1) described above, that is, when the stick-in occurs with the head-side oil chamber 9a at a higher pressure than the rod-side oil chamber 9b (the differential pressure (Ph-Pr) is "positive"), if the value of the differential pressure (Ph-Pr) is relatively small (smaller than the preset value α, in the range of 0 < differential pressure (Ph-Pr) < α as shown in Figure 5(B)), the correction value Cp is set to "1" due to the physical limitation of the maximum flow rate of the hydraulic pump 11. As a result, when the differential pressure (Ph-Pr) is small, the corrected pump flow rate obtained by the corrected pump flow rate calculation unit 28 becomes equal to the basic pump flow rate obtained by the first map 26. On the other hand, when the differential pressure (Ph-Pr) increases, as shown in the first quadrant of Figure 4, the operating speed of the stick cylinder 9 decreases as the differential pressure (Ph-Pr) increases. Therefore, in order to correct the pump flow rate to be reduced in accordance with the reduced operating speed, the correction value Cp is set to decrease as the differential pressure (Ph-Pr) increases. This prevents problems such as the pump flow rate decreasing as the differential pressure (Ph-Pr) increases, resulting in excessive pump flow relative to the operating speed of the stick cylinder 9 and causing a boost state. Furthermore, in the case of (2) described above, that is, when the stick-in is performed with a higher pressure in the rod-side oil chamber 9b than in the head-side oil chamber 9b (the differential pressure (Ph-Pr) is "negative"), the regeneration flow rate increases as the absolute value of the differential pressure |Ph-Pr| increases, and the supply flow rate to the stick cylinder 9 increases by the amount of this regeneration flow rate, causing the operating speed of the stick cylinder 9 to increase. Therefore, in order to reduce the pump flow rate by the amount of the regeneration flow rate, the correction value Cp is set to decrease as the absolute value of the differential pressure |Ph-Pr| increases. This prevents the pump flow rate from becoming excessive relative to the operating speed of the stick cylinder 9 by reducing the pump flow rate as the absolute value of the differential pressure |Ph-Pr| increases. The shape of Figure 5(B) thus set is similar to the shape of the portion of the stick cylinder operating speed in the first and second quadrants of Figure 4 that is contributed to by the pump supply flow rate.

[0032] In the configuration described above, the hydraulic excavator 1 is equipped with a boom 5 supported on the machine body (upper rotating body 2) so as to be able to move up and down, and a stick 6 supported on the tip of the boom 5 so as to be able to swing, and the swinging of the stick 6 is configured to be performed based on the extension and retraction operation of the stick cylinder 9. In providing the hydraulic excavator 1 with a control system to control the pump flow rate of a variable-capacity hydraulic pump 11 which is the source of pressurized oil for the stick cylinder 9, the control system is equipped with an operation detection means 21 that detects the operation of an operating tool for the stick for operating the stick cylinder 9, a head-side pressure sensor 23 and a rod-side pressure sensor 24 for detecting the differential pressure between the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9, and a control device 17 that outputs a control signal to the variable-capacity means 11a of the hydraulic pump 11 based on the input signals from these operation detection means 21 and the head-side and rod-side pressure sensors 23 and 24. The control device 17 includes a first map 26 that sets the basic pump flow rate according to the amount of operation of the stick control tool input from the operation detection means 21, and a second map 27 that sets a correction value Cp to correct the basic pump flow rate set in the first map 26 according to the differential pressure (Ph-Pr) between the pressure Ph of the head-side oil chamber 9a and the pressure Pr of the rod-side oil chamber 9b input from the head-side and rod-side pressure sensors 23 and 24. The control device 17 corrects the basic pump flow rate set in the first map 26 using the correction value Cp set in the second map 27 and outputs a control signal to the variable capacity means 11a of the hydraulic pump 11 to achieve the corrected pump flow rate.

[0033] In this embodiment, the basic pump flow rate, which is set according to the amount of operation of the stick control tool, is corrected using a correction value Cp set according to the differential pressure (Ph-Pr) between the pressure Ph in the head-side oil chamber 9a and the pressure Pr in the rod-side oil chamber 9b, and the hydraulic pump 11 is controlled to achieve the corrected pump flow rate. As a result, even if the differential pressure (Ph-Pr) between the head-side oil chamber 9a and the rod-side oil chamber 9b fluctuates due to the posture of the stick 6 or the weight of the load in the bucket 7, and this difference in differential pressure (Ph-Pr) causes a difference in the operating speed of the stick cylinder 9, the pump flow rate corresponding to the operating speed of the stick cylinder 9 is supplied. This effectively avoids problems such as excessive or insufficient pump flow to the stick cylinder 9, resulting in boost or vacuum conditions, enabling efficient pump flow rate control and contributing to improved operability. Furthermore, this system determines the conditions of factors affecting the operating speed of the stick cylinder 9 (such as the posture of the stick 6 and the weight of the load) based on the differential pressure (Ph-Pr) between the head-side oil chamber 9a and the rod-side oil chamber 9b. Therefore, it does not require expensive equipment such as position detectors to detect the posture of the stick 6, contributing to cost reduction, and also has the advantage of being easy to control.

[0034] In this configuration, the second map 27 is configured to set separate correction values ​​Cp for the extension side (in side) and the retraction side (out side) of the stick cylinder 9. This allows for efficient pump flow rate control using separate correction values ​​Cp for the extension and retraction sides, depending on factors such as the difference in operating speed due to the difference in piston pressure receiving area between the head-side oil chamber 9a and the rod-side oil chamber 9b, and the presence or absence of a regeneration circuit that supplies discharged oil from the high-pressure side oil chamber to the low-pressure side oil chamber.

[0035] Furthermore, in this embodiment, the correction value Cp set by the second map 27 is a value between 0 and 1 (0 ≤ Cp ≤ 1) that is multiplied by the basic pump flow rate set in the first map 26. The pump flow rate corrected using this correction value Cp will be less than or equal to the basic pump flow rate. In this case, when the differential pressure (absolute value of differential pressure |Ph-Pr|) between the head-side oil chamber 9a and the rod-side oil chamber 9b is small, the value of the correction value Cp is "1" or close to "1", and when the differential pressure (absolute value of differential pressure |Ph-Pr|) is large, the value of the correction value Cp approaches 0. As a result, in the region where the differential pressure is small and hardly affects the operating speed of the stick cylinder 9, the corrected pump flow rate can be made equivalent to the basic pump flow rate, while in the region where the differential pressure is large and is affected by horsepower control, the corrected pump flow rate can be reduced, thereby enabling more efficient pump flow rate control.

[0036] Furthermore, the control system of the hydraulic excavator 1 includes a regeneration circuit (in this embodiment, a regeneration valve passage 14f of the stick control valve 14) that supplies the discharged oil from the rod-side oil chamber 9b of the stick cylinder 9 to the head-side oil chamber 9a, and the second map 27 sets a correction value Cp to reduce the pump flow rate by the amount of regeneration flow rate corresponding to the differential pressure between the rod-side oil chamber 9a and the head-side oil chamber 9a. This enables more efficient pump flow rate control.

[0037] Furthermore, in this embodiment, the second map 27 is created based on measured data relating the differential pressure (Ph-Pr) between the head-side oil chamber 9a and the rod-side oil chamber 9b of the stick cylinder 9 and the operating speed of the stick cylinder 9. This makes it possible to create a highly accurate second map 27 that corresponds to the actual machine.

[0038] It should be noted that the present invention is not limited to the above-described embodiment. For example, in this embodiment, the correction value of the second map was set based on measured data of the relationship between the operating speed and differential pressure of the stick cylinder, but it is not necessarily required to use measured data, and the correction value can be set by calculation or other means. Furthermore, although this embodiment describes pump flow rate control when only the stick cylinder is operated, the operating state of hydraulic cylinders other than the stick cylinder, such as boom cylinders and bucket cylinders, can also be estimated based on the differential pressure between the head-side oil chamber and the rod-side oil chamber, and the pump supply flow rate corresponding to the operating state can be determined, and the total pump flow rate of the hydraulic pump can be distributed according to the pump flow rate of each hydraulic cylinder determined accordingly. [Industrial applicability]

[0039] This invention can be used to control the pump flow rate of a hydraulic pump in construction machinery such as hydraulic excavators. [Explanation of Symbols]

[0040] 1. Hydraulic excavator 5 Boom 6 sticks 9 Stick Cylinder 9a Head-side oil chamber 9b Rod-side oil chamber 11. Hydraulic pump 11a Variable capacity means 14f Valve for regeneration 17 Control device 21 Operation detection means 23 Head-side pressure sensor 24 Rod-side pressure sensor 25 Pump flow control unit 26 First Map 27 Second Map 28 Correction pump flow rate calculation unit

Claims

1. In a construction machine comprising a boom supported on the machine body so as to be able to move up and down, and a stick supported at the tip of the boom so as to be able to swing, wherein the swing of the stick is configured to be performed based on the extension and retraction operation of a stick cylinder, a control system is provided to control the pump flow rate of a variable-capacity hydraulic pump that serves as the supply source of pressurized oil for the stick cylinder, An operation detection means for detecting the operation of a stick-type operating tool for operating a stick cylinder, A pressure detection means for detecting the differential pressure between the head-side oil chamber and the rod-side oil chamber of a stick cylinder, A control device is provided that outputs a control signal to the variable capacity means of the hydraulic pump based on the input signals from these operation detection means and pressure detection means. The control device is A first map sets the basic pump flow rate according to the amount of operation of the stick control device input from the operation detection means, The system includes a second map which sets a correction value to correct the basic pump flow rate set in the first map according to the differential pressure between the head-side oil chamber and the rod-side oil chamber input from the pressure detection means, A control system for construction machinery characterized by correcting the basic pump flow rate set in the first map using a correction value set in the second map, and outputting a control signal to the variable capacity means of the hydraulic pump to achieve the corrected pump flow rate.

2. The control system for a construction machine according to claim 1, characterized in that the second map sets correction values ​​separately for the extension side and the contraction side of the stick cylinder.

3. A control system for construction machinery according to claim 1, characterized in that the correction value set by the second map is a numerical value of 0 or more and 1 or less that is multiplied by the basic pump flow rate, and the correction value is set to be 1 or close to 1 when the differential pressure between the head-side oil chamber and the rod-side oil chamber is small, and the correction value approaches 0 when the differential pressure is large.

4. The control system for a construction machine according to claim 1 is characterized in that the control system includes a regeneration circuit that supplies discharged oil from the rod-side oil chamber of a stick cylinder to the head-side oil chamber, and the second map sets a correction value to reduce the pump flow rate by the amount of regeneration flow rate corresponding to the differential pressure between the rod-side oil chamber and the head-side oil chamber.

5. A control system for construction machinery, characterized in that, according to any one of claims 1 to 4, the second map is created based on data obtained by actually measuring the relationship between the differential pressure between the head-side oil chamber and the rod-side oil chamber of the stick cylinder and the operating speed of the stick cylinder.

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