Hydraulic control system

Abstract

Problem to be solved: When a flow control valve is installed upstream of the directional control valve to change the relationship between the supply flow rate and the discharge flow rate of the hydraulic actuator, how to avoid an oversized directional control valve and enable precise control of the supply flow rate? Solution: The configuration controls the supply flow rate to the lever cylinder (8) based on the opening area of ​​the directional control valve (25) and the flow control valve (28) of the lever; the target opening area of ​​the flow control valve (28) of the lever is calculated based on the target supply flow rate from hydraulic pumps A and B to the lever cylinder (8), the opening area of ​​the directional control valve (25) of the lever, and the target differential pressure between the load pressure of hydraulic pump A and the lever cylinder (8); the flow control valve (28) of the lever is controlled to maintain the calculated target opening area.

Description

Technical Field

[0001] This invention relates to the technical field of a hydraulic control system used in operating machinery having hydraulic actuators, such as hydraulic excavators. Background Technology

[0002] Typically, operating machinery such as hydraulic excavators is equipped with various types of hydraulic actuators. As a hydraulic control system for controlling the supply / discharge of these hydraulic actuators, a conventional configuration is known, for example, that includes a single spool valve for simultaneously performing direction-changing control to switch the supply / discharge direction of hydraulic oil for the hydraulic actuators, a supply flow control for controlling the supply flow rate from the hydraulic pump to the hydraulic actuators, and a discharge flow control for controlling the discharge flow rate from the hydraulic actuators to the tank. However, when a single spool valve controls the supply / discharge flow rates, a problem arises in terms of reduced operating efficiency and operability because the relationship between the opening area on the supply side and the opening area on the discharge side relative to the moving position of the valve core is uniquely determined. This problem cannot be addressed by changing the relationship between the supply and discharge flow rates according to the operating conditions, such as individual operation actuating a single hydraulic actuator and combined operation actuating multiple hydraulic actuators simultaneously, or various operations such as light-load and heavy-load work.

[0003] To address this problem, a conventional technique exists for independently controlling the supply flow rate to and from a hydraulic actuator. This technique includes a flow control valve for controlling the supply flow rate from the hydraulic pump to the hydraulic actuator; a directional valve disposed downstream of the flow control valve for switching the supply / discharge direction of hydraulic oil relative to the hydraulic actuator and controlling the discharge flow rate from the hydraulic actuator; and a control device for controlling these flow control valves and directional valves (see, for example, Patent Document 1). In this technique, the directional valve is configured to not control the supply flow rate by providing a large opening area in the supply valve passage formed on the directional valve, allowing the supply flow to enter the hydraulic actuator as is. This enables each individual valve to independently control the supply / discharge flow rate to / from the hydraulic actuator, and reduces the number of parts compared to a configuration using three different valves to control the directional valve for both supply / discharge switching control and discharge flow rate control.

[0004] Furthermore, in the aforementioned Patent Document 1, a high-flow-rate hydraulic actuator using a first hydraulic pump and a second hydraulic pump as hydraulic supply sources is configured with two flow control valves. The first flow control valve controls the supply flow rate from the first hydraulic pump, and the second flow control valve controls the supply flow rate from the second hydraulic pump. The total flow rate from the two flow control valve pumps is supplied to the hydraulic actuator through a supply valve passage formed on a directional control valve, for directional control and discharge flow rate control. Therefore, even in a high-flow-rate hydraulic actuator that supplies pressurized oil from two hydraulic pumps to individually control the supply / discharge flow rates, only a single directional control valve is required, thus simplifying the circuit. It allows for individual control of the supply flow rates from the first and second hydraulic pumps and enables high-precision control of pump flow rate distribution during combined operation.

[0005] Existing technical documents

[0006] [Patent Literature]

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-20604. Summary of the Invention

[0008] [The problem this invention aims to solve]

[0009] In Patent Document 1, as described above, the directional control valve is configured to supply flow to the hydraulic actuator by means of a flow control valve; that is, the directional control valve is configured not to control the supply flow rate. Here, by making the opening area of ​​the supply valve passage leading to the directional control valve so large that there is no pressure difference before and after the valve, the supply flow rate to the hydraulic actuator can be controlled solely by controlling the opening area of ​​the flow control valve. However, in order to form a valve passage with such a large opening, the size of the directional control valve must be set large. In particular, for the directional control valve of a high-flow hydraulic actuator using two hydraulic pumps as hydraulic supply sources, a large-opening supply valve passage is required to allow the supply flow from the two hydraulic pumps to pass through without any pressure difference before and after the directional control valve, thus creating the problem that the directional control valve becomes quite large. Therefore, it has been proposed to install a flow control valve upstream of the directional control valve without making the opening area of ​​the supply valve passage to the directional control valve so large that there is no pressure difference before and after the valve. However, not only the opening area of ​​the flow control valve, but also the opening area from the supply valve passage to the directional valve can affect flow control and may make it difficult to control the supply flow to the hydraulic actuator. Therefore, this is the problem that the present invention aims to solve.

[0010] [Methods to solve this problem]

[0011] The object of this invention is to solve the problems considered in the above-mentioned current situation; claim 1 of this invention is a hydraulic control system comprising a hydraulic pump and a hydraulic actuator using the hydraulic pump as a hydraulic supply source, wherein the system is provided with a directional switching valve having a supply / discharge valve passage for the hydraulic actuator and switching the supply / discharge direction; a flow control valve disposed upstream of the directional switching valve for controlling the supply flow rate from the hydraulic pump to the directional switching valve; and a control device for controlling the operation of the directional switching valve and the flow control valve; wherein the discharge flow rate for the hydraulic actuator is controlled by a configuration based on the opening area of ​​the discharge valve passage from the directional switching valve, and the supply flow rate is controlled by a configuration based on the opening area of ​​the supply valve passage to the directional switching valve and the opening area of ​​the flow control valve; wherein The control device includes: a target supply flow rate setting device, which sets a target supply flow rate from the hydraulic pump to the hydraulic actuator based on the operation amount of the actuator's controller; a directional switching valve opening area setting device, which sets the opening area of ​​the supply / discharge valve passage for the directional switching valve based on the operation amount of the actuator's controller; a target differential pressure setting device, which sets a target differential pressure between the hydraulic pump pressure and the load pressure of the hydraulic actuator; and a calculation device, which calculates the target opening area of ​​the flow control valve supplying the target supply flow rate to the hydraulic actuator based on the aforementioned preset target supply flow rate, the opening area of ​​the supply valve passage to the directional switching valve, and the target differential pressure; and wherein the control device controls the operation of the flow control valve to maintain the target opening area calculated by the calculation device.

[0012] Claim 2 of the present invention is the hydraulic control system according to claim 1, wherein when calculating the target opening area of ​​the flow control valve, the calculation device calculates the differential pressure before and after the supply valve channel to the directional switching valve based on the target supply flow rate and the opening area of ​​the supply valve channel to the directional switching valve, further calculates the differential pressure before and after the flow control valve based on the differential pressure before and after the supply valve channel to the directional switching valve and the target differential pressure, and calculates the target opening area of ​​the flow control valve based on the differential pressure before and after the flow control valve and the target supply flow rate.

[0013] Claim 3 of the present invention is a hydraulic control system according to claim 1, wherein the hydraulic control system comprises: first and second hydraulic pumps; a high-flow hydraulic actuator that uses both the first and second hydraulic pumps as hydraulic supply sources; a directional control valve having a supply / discharge valve passage for the high-flow hydraulic actuator and switching the supply / discharge direction; a main / secondary supply passage that respectively connects the first and second hydraulic pumps to the pump port of the directional control valve; wherein the system is arranged with a flow control valve for controlling the supply flow rate from the second hydraulic pump to the directional control valve located in the secondary supply passage; when the operating amount of the actuator of the high-flow hydraulic actuator is less than a set value, by closing the flow control valve, only the supply flow rate through the main supply passage is configured to be supplied from the first hydraulic pump to the directional control valve; when the operating amount of the actuator of the high-flow hydraulic actuator is not less than the set value, by opening the flow control valve, the supply flow rate from the second hydraulic pump through the secondary supply passage and the supply flow rate from the first hydraulic pump through the main supply passage are configured to be connected together to be supplied to the directional control valve; wherein the discharge flow rate of the high-flow hydraulic actuator is... The system is configured to control the flow rate based on the opening area of ​​the discharge valve passage from the directional control valve; if the flow control valve is closed, the supply flow rate is configured to control the flow rate based on the opening area from the supply valve passage to the directional control valve; and if the flow control valve is open, the supply flow rate is configured to control the flow rate based on both the opening area of ​​the flow control valve and the opening area from the supply valve passage to the directional control valve; wherein the target supply flow rate setting device of the control device sets a target supply flow rate from the first and second hydraulic pumps to the high-flow hydraulic actuator for each hydraulic pump according to the operation amount of the actuator of the high-flow hydraulic actuator; the opening area setting device of the directional control valve sets the opening area of ​​the supply / discharge valve passage for the directional control valve according to the operation amount of the actuator of the high-flow hydraulic actuator; the target differential pressure setting device sets a target differential pressure between the pressure of the second hydraulic pump and the load pressure of the high-flow hydraulic actuator; and the calculation device calculates the target opening area of ​​the flow control valve for supplying the target supply flow rate from the second hydraulic pump to the high-flow hydraulic actuator based on the above-preset target supply flow rate, the opening area from the supply valve passage to the directional control valve, and the target differential pressure.

[0014] Claim 4 of the present invention is the hydraulic control system according to claim 3, wherein when calculating the target opening area of ​​the flow control valve, the calculation device calculates the differential pressure before and after the supply valve passage to the directional control valve based on the target supply flow rate from the first and second hydraulic pumps to the hydraulic actuator and the opening area of ​​the supply valve passage to the directional control valve, further calculates the differential pressure before and after the flow control valve based on the differential pressure before and after the supply valve passage to the directional control valve and the target differential pressure, and calculates the target opening area of ​​the flow control valve based on the differential pressure before and after the flow control valve and the target supply flow rate from the second hydraulic pump to the hydraulic actuator.

[0015] [Beneficial Effects of the Invention]

[0016] According to the invention of claim 1, although the relationship between the supply flow rate to the hydraulic actuator and the discharge flow rate from the hydraulic actuator can be changed, the directional switching valve can be prevented from becoming larger and highly precise supply flow control can be provided.

[0017] According to claim 2, the target opening area of ​​the flow control valve can be accurately calculated, which helps to improve the accuracy of supply flow control.

[0018] According to the invention of claim 3, in the same high-flow hydraulic actuator using the first and second hydraulic pumps as hydraulic supply sources, the directional valve can be enlarged and highly precise supply flow control can be provided, although the relationship between the supply flow rate to the high-flow hydraulic actuator and the discharge flow rate from the high-flow hydraulic actuator can be varied over a wide range of supply flow rates of pressurized oil supplied from the two hydraulic pumps.

[0019] According to the invention of claim 4, the target opening area of ​​the flow control valve for a high-flow hydraulic actuator can be accurately calculated, which helps to improve the accuracy of supply flow control. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the hydraulic circuit of the first embodiment.

[0021] Figure 2 This is a block diagram illustrating the inputs and outputs of the controller.

[0022] Figure 3 This is a schematic diagram showing the relationship between the operating amount of the joystick, the target supply flow rate of the first and second hydraulic pumps, the opening area of ​​the flow control valve of the joystick, and the opening area of ​​the direction switching valve of the joystick when the joystick is operated alone.

[0023] Figure 4 This is a schematic diagram showing the combined state of the directional control valve and the flow control valve of the joystick.

[0024] Figure 5 This is a schematic diagram of the hydraulic circuit of the second embodiment. Detailed Implementation

[0025] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0026] first, Figure 1 This is a schematic diagram of the hydraulic circuit of a first embodiment of the hydraulic control system of a hydraulic excavator implementing the present invention; in Figure 1In the diagram, symbols A and B indicate variable capacity hydraulic pumps; symbols Aa and Ba indicate variable capacity devices that change the capacity of hydraulic pumps A and B based on control signals sent from controller 10 (mentioned later); symbol 3 indicates an oil tank; symbol 4 indicates a left travel motor; symbol 5 indicates a right travel motor; symbol 6 indicates a boom cylinder; symbol 7 indicates a swing motor; symbol 8 indicates a joystick cylinder; and symbol 9 indicates a bucket cylinder. The aforementioned left / right travel motors 4 and 5; boom cylinder 6; swing motor 7; joystick cylinder 8; and bucket cylinder 9 are hydraulic actuators that use hydraulic pumps A and B as hydraulic supply sources; among these hydraulic actuators, boom / joystick cylinders 6 and 8 are hydraulic actuators that use two hydraulic pumps A and B as hydraulic supply sources, and correspond to the high-flow hydraulic actuators of this invention. Note that boom cylinder 6, control lever cylinder 8, and bucket cylinder 9 are hydraulic cylinders that extend and retract to swing and form the boom, control lever, and bucket (not shown) of the front working equipment of the hydraulic excavator, respectively; left / right travel motors 4 and 5 are hydraulic motors used to drive the left and right travel bodies of the hydraulic excavator from front to back, respectively; and slewing motor 7 is a hydraulic motor used to make the upper slewing body of the hydraulic excavator slew left and right.

[0027] Hydraulic pump A is connected to pump line C at the first position X (mentioned later) via straight travel valve 11 and left travel direction switching valve 13. Additionally, hydraulic pump B is connected to pump line D and right travel direction switching valve 14 at the first position X via straight travel valve 11.

[0028] The straight-line travel valve 11 is a bidirectional switching valve that switches between a first position X and a second position Y based on a control signal output from the controller 10. When the straight-line travel valve 11 is in the first position X, hydraulic pump A's delivery oil is supplied to pump line C and the left travel direction switching valve 13, and hydraulic pump B's delivery oil is supplied to pump line D and the right travel direction switching valve 14. When the straight-line travel valve 11 is in the second position Y, hydraulic pump A's delivery oil is supplied to the left and right travel direction switching valves 13 and 14, and hydraulic pump B's delivery oil is supplied to pump lines C and D. The controller 10 switches the straight-line travel valve 11 to the first position X and the second position Y according to the operation of the left and right travel actuators (not shown) or other hydraulic actuators (for boom, swing, joystick, and bucket, all not shown), thereby setting the supply flow rate to the left / right travel motors 4 and 5 to the same flow rate during straight-line travel. Note that the following description pertains to the situation where the straight-line driving valve 11 is in the first position X, i.e., the delivery oil from hydraulic pump A is supplied to pump line C and the left driving direction switching valve 13, and the delivery oil from hydraulic pump B is supplied to pump line D and the right driving direction switching valve 14.

[0029] The left and right driving direction switching valves 13 and 14 are closed center spool valves that control the supply / discharge flow rate of the left / right driving motors 4 and 5 and change the supply / discharge direction. They also include front / rear pilot ports 13a, 13b, 14a and 14b connected to the driving proportioning solenoid valves (left driving front side / left driving rear side / right driving front side / right driving rear side proportioning solenoid valves, all not shown) for outputting pilot pressure based on the control signal output from the controller 10. When pilot pressure is not input into the front / rear pilot ports 13a, 13b, 14a, and 14b, the left and right driving direction switching valves 13 and 14 are positioned in neutral position N, in which oil is neither supplied to nor discharged from the left / right driving motors 4 and 5; when pilot pressure is input into the front pilot ports 13a and 14a, the left and right driving direction switching valves 13 and 14 are configured to switch to the front operating position X, opening the supply valve passages 13e and 14e, thereby supplying the delivery oil from hydraulic pumps A and B to the left / right driving motors 4 and 5. The front side ports 4a and 5a of the left and right travel motors 4 and 5 are opened, and the drain valve passages 13f and 14f are opened, thereby draining oil from the rear side ports 4b and 5b to the oil tank 3; in addition, when the pilot pressure is input to the rear side pilot ports 13b and 14b, the valves 13 and 14 are configured to switch to the rear operating position Y to open the supply valve passages 13e and 14e, thereby supplying the delivery oil from the hydraulic pumps A and B to the rear side ports 4b and 5b of the left and right travel motors 4 and 5, and opening the drain valve passages 13f and 14f, thereby draining oil from the front side ports 4a and 5a to the oil tank 3. When valves 13 and 14 are in the forward or rearward operating position X or Y, the supply and discharge flow rates of the left / right travel motors 4 and 5 are controlled by the opening areas of the supply valve passages 13e and 14e and the discharge valve passages 13f and 14f. The opening areas are increased or decreased based on the valve core movement position associated with the increase or decrease of the pilot pressure output from the travel proportional solenoid valve to the forward / rear side pilot ports 13a, 13b, 14a, and 14b. Furthermore, when the left and right travel actuators are operated, the controller 10 controls the travel proportional solenoid valves to output pilot pressure, which increases or decreases according to the amount of travel actuator operation, thereby enabling the left and right travel motors 4 and 5 to be driven at a rate corresponding to the amount of travel actuator operation.

[0030] In addition, the main side oil supply channel 17 of the boom, the secondary side oil supply channel 18 of the control lever, and the oil supply channel 19 of the bucket branch parallel to each other from the pump line C connected to the hydraulic pump A; in addition, the secondary side oil supply channel 20 of the boom, the swing oil supply channel 21, and the main side oil supply channel 22 of the control lever branch parallel to each other from the pump line D connected to the hydraulic pump B. The main side oil supply channel 17 and the secondary side oil supply channel 20 of the boom are oil channels that connect hydraulic pumps A and B to pump ports 23p on the boom direction control valve 23 (described later); in addition, the main side oil supply channel 22 and the secondary side oil supply channel 18 of the control lever are oil channels that connect hydraulic pumps B and A to pump ports 25p on the control lever direction control valve 25; the swing oil supply channel 21 is an oil channel that connects hydraulic pump B to pump port 24p on the swing direction control valve 24; and the bucket oil supply channel 19 is an oil channel that connects hydraulic pump A to pump port 26p on the bucket direction control valve 26.

[0031] The flow control valve 28 of the control lever is installed on the secondary oil supply channel 18 of the control lever and is used to control the supply flow rate from hydraulic pump A to the direction switching valve 25 of the control lever; in addition, the flow control valve 29 of the boom is installed on the secondary oil supply channel 20 of the boom and is used to control the supply flow rate from hydraulic pump B to the direction switching valve 23 of the boom. These flow control valves 28 and 29 of the control lever / boom are controlled by the flow control proportional solenoid valves 45 and 46 of the control lever / boom. Figure 2 (As shown in the diagram) The lifting valve pilot operates, and the proportional solenoid valves 45 and 46 operate based on the control signal for flow control output from the controller 10, and have a backflow prevention function to allow oil to flow from the hydraulic pumps A and B to the direction switching valves 25 and 23 of the joystick / boom and to prevent backflow.

[0032] Furthermore, flow control valves such as the boom / arm flow control valves 28 and 29 are not located on the boom / arm main supply channels 17 and 22 and the bucket / swing supply channels 19 and 21; the supply flow from hydraulic pump A or B through these boom / arm main supply channels 17 and 22 and the bucket / swing supply channels 19 and 21 will be supplied as is to the direction switching valves 23, 26, 24, and 25 for the boom, bucket, swing, and boom / arm without flow rate control. A check valve 30 is located on each of the boom / arm main supply channels 17 and 22 and the bucket / swing supply channels 19 and 21, allowing oil to flow from hydraulic pumps A and B to the direction switching valves 23, 26, 24, and 25 for the boom, bucket, swing, and boom / arm, while preventing backflow.

[0033] Therefore, pressurized oil is supplied from hydraulic pumps A and B to pump port 23p on the boom's direction switching valve 23 via the boom's main / secondary side oil supply channels 17 and 20, respectively; and the flow rate of pressurized oil from hydraulic pump B is controlled (or interrupted) by the boom's flow control valve 29 located on the secondary side oil supply channel 20, to supply the boom's direction switching valve 23. Furthermore, pressurized oil from hydraulic pumps B and A is supplied to pump port 25p on the control lever's direction switching valve 25 via the control lever's main and secondary side oil supply channels 22 and 18, respectively; and the flow rate of pressurized oil from hydraulic pump A is controlled (or interrupted) by the control lever's flow control valve 28 located on the control lever's secondary side oil supply channel 18, to supply the control lever's direction switching valve 25.

[0034] Next, instructions are provided for the direction switching valves 23 to 26 used for the boom, swing, control stick, and bucket.

[0035] Description is provided regarding the swing / bucket direction switching valves 24 and 26, wherein pressurized oil is supplied from either hydraulic pump A or B. Swing direction switching valve 24 is a closed center spool valve used to control the supply / discharge flow rate of the swing motor 7 and to change its supply / discharge direction; valve 24 has left / right steering pilot ports 24a and 24b, which are respectively connected to left / right steering proportional solenoid valves 42a and 42b for outputting pilot pressure based on a control signal output from controller 10. Figure 2(as shown in the diagram); pump port 24p, which is connected to the rotary oil supply channel 21; tank port 24t, which is connected to the tank line T of the oil tank 3; first actuator port 24c, which is connected to the left steering port 7a on the rotary motor 7; and second actuator port 24d, which is connected to the right steering port 7b on the rotary motor 7. Furthermore, when no pilot pressure is input to the left / right steering pilot ports 24a, 24b, the slewing direction switching valve 24 is in neutral position N, where the supply / discharge of the slewing motor 7 is uncontrolled; when pilot pressure is input to the left steering pilot port 24a, the valve 24 is configured to switch to the left steering operating position X to open the supply valve passage 24e from the pump port 24p to the first actuator port 24c and the discharge valve passage 24f from the second actuator port 24d to the housing port 24t; furthermore, when pilot pressure is input to the right steering pilot port 24b, the valve 24 is configured to switch to the right steering operating position Y to open the supply valve passage 24e from the pump port 24p to the second actuator port 24d and the discharge valve passage 24f from the first actuator port 24c to the housing port 24t. When valve 24 is in the left / right steering operation position X or Y, the supply / discharge flow rate for the rotary motor 7 will be controlled by the opening area of ​​the supply / discharge valve passages 24e, 24f, and the opening area will be controlled to increase or decrease according to the valve core movement position associated with the increase or decrease of the pilot pressure output from the left / right steering proportional solenoid valves 42a, 42b to the left / right steering pilot ports 24a, 24b.

[0036] The bucket direction switching valve 26 is a closed center slide valve used to control the supply / discharge flow rate of the bucket cylinder 9 and change the supply / discharge direction; the valve 26 has extension / retraction side pilot ports 26a and 26b, which are respectively connected to the extension / retraction side proportional solenoid valves 44a and 44b of the bucket. Figure 2(shown in the figure) for outputting pilot pressure based on a control signal output from controller 10; pump port 26p, which is connected to bucket supply oil passage 19; tank port 26t, which is connected to tank line T; first actuator port 26c, which is connected to head side port 9a on bucket cylinder 9; and second actuator port 26d, which is connected to rod side port 9b on bucket cylinder 9. The bucket direction switching valve 26 has the same structure as the swing direction switching valve 24 described above. When the valve 26 is switched from the neutral position N to the extension / retraction operation position X or Y, the valve 26 is configured to open the supply valve passage 26e from the pump port 26p to the actuator port 26c or 26d and the discharge valve passage 26f from the actuator port 26d or 26c to the tank port 26t, and control the supply / discharge flow rate according to the opening area of ​​the supply / discharge valve passages 26e and 26f to / from the bucket cylinder 9; and control the opening area to increase or decrease according to the increase or decrease of the pilot pressure output from the extension / retraction side proportional solenoid valves 44a and 44b of the bucket according to the valve core movement position.

[0037] Next, a description is provided regarding the directional control valves 25 and 23 of the control lever / boom that supply pressurized oil from two hydraulic pumps A and B. The directional control valve 25 is a closed center spool valve used to control the supply / discharge / recirculation flow rate of the control lever cylinder 8 and to switch the supply / discharge direction; valve 25 has extension / retraction side pilot ports 25a and 25b, which are respectively connected to the extension / retraction side proportional solenoid valves 43a and 43b of the control lever. Figure 2(As shown in the diagram), a pilot pressure is output based on a control signal from controller 10; a pump port 25p is connected to the main / secondary side oil supply channels 22, 18 of the joystick; a tank port 25t is connected to the tank line T; a first actuator port 25c is connected to the head side port 8a on the joystick cylinder 8; and a second actuator port 25d is connected to the lever side port 8b on the joystick cylinder 8. Furthermore, when no pilot pressure is input to the extension / retraction side pilot ports 25a, 25b, the joystick direction switching valve 25 is in the neutral position N, where the supply / discharge of the joystick cylinder 8 is uncontrolled; when pilot pressure is input to the extension side pilot port 25a, the valve 25 is configured to switch to the extension side operating position X to open the supply valve channel 25e from the pump port 25p to the first actuator port 25c, and from the second actuator port 25d to the tank port 25t. The system includes a discharge valve passage 25f and a recirculation valve passage 25g that supplies a portion of the discharged oil as regenerated oil from the second actuator port 25d to the first actuator port 25c. Furthermore, when pilot pressure is input to the contraction-side pilot port 25b, valve 25 is configured to switch to the contraction-side operating position Y to open the supply valve passage 25e from the pump port 25p to the second actuator port 25d and the discharge valve passage 25f from the first actuator port 25c to the tank port 25t. The opening areas of the supply / discharge / recirculation valve passages 25e, 25f, and 25g are controlled to increase or decrease according to the valve core position moved by the pilot pressure output from the extension / contraction-side proportional solenoid valves 43a and 43b of the control lever, and the discharge / recirculation flow rate from the control lever cylinder 8 is controlled by the opening areas of the discharge / recirculation valve passages 25f and 25g. When the flow control valve 28 of the joystick closes the secondary oil supply channel 18 of the joystick, the supply flow rate to the joystick cylinder 8 will be controlled by the opening area of ​​the supply valve channel 25e on the joystick direction switching valve 25; when the flow control valve 28 of the joystick opens the secondary oil supply channel 18 of the joystick, the supply flow rate will be controlled by the opening area of ​​the flow control valve 28 of the joystick and the opening area of ​​the supply valve channel 25e on the joystick direction switching valve 25.

[0038] Furthermore, the boom direction switching valve 23 is a closed center spool valve used to control the supply / discharge / recirculation flow rate of the boom cylinder 6 and to switch the supply / discharge direction; valve 23 has extension / retraction side pilot ports 23a and 23b, which are respectively connected to the extension / retraction side proportional solenoid valves 41a and 41b of the boom. Figure 2(shown in the figure) is used to output pilot pressure based on the control signal output from the controller 10; pump port 23p is connected to the main / auxiliary side oil supply channels 17, 20 of the boom; box port 23t is connected to the box line T; first actuator port 23c is connected to the head side port 6a on the boom cylinder 6; second actuator port 23d is connected to the rod side port 6b on the boom cylinder 6. The boom direction switching valve 23 has the same structure as the control lever direction switching valve 25 described above; when the valve 23 is switched from the neutral position N to the extension / retraction operation position X or Y, the valve 23 is configured to open the supply valve passage 23e from the pump port 23p to the actuator port 23c or 23d and the discharge valve passage 24f from the actuator port 23d or 23c to the tank port 23t; and when the valve 23 is in the retraction side operation position Y, the valve 23 is configured to open the recirculation valve passage 23g, which supplies a portion of the discharged oil as regenerated oil from the first actuator port 23c to the second actuator port 23d. The opening areas of the supply / discharge / recirculation valve passages 23e, 23f, and 23g are controlled to increase or decrease according to the valve spool position moved by the pilot pressure output from the boom extension / retraction side proportional solenoid valves 41a and 41b, and the discharge / recirculation flow rate to the boom cylinder 6 is controlled by the opening areas of the discharge / recirculation valve passages 23f and 23g. When the boom flow control valve 29 closes the boom auxiliary side oil supply passage 20, the supply flow rate to the boom cylinder 6 is controlled by the opening area of ​​the supply valve passage 23e to the boom direction switching valve 23; when the boom flow control valve 29 opens the boom auxiliary side oil supply passage 20, the supply flow rate to the boom cylinder 6 is controlled by the opening area of ​​the boom flow control valve 29 and the opening area of ​​the supply valve passage 23e to the boom direction switching valve 23.

[0039] Furthermore, in Figure 1 In the diagram, symbols E and F indicate discharge lines branching off upstream of all directional switching valves 13, 14, 23 to 26 connected to pump lines C and D to tank line T, and discharge valves 31 and 32 are located on discharge lines E and F. These discharge valves 31 and 32 are controlled by discharge proportional solenoid valves 47a and 47b. Figure 2 (As shown in the figure) The pilot pressure output is operated to control the increase or decrease of the discharge flow rate from hydraulic pumps A and B through discharge lines E and F to oil tank 3; and the discharge proportional solenoid valves 47a and 47b control the increase or decrease of the pilot pressure output to discharge valves 31 and 32 based on the control signal output from controller 10.

[0040] like Figure 2As shown in the block diagram, the controller 10 (corresponding to the control device in this invention) is configured to input signals from: a boom operation detection device 50 for detecting the operating direction and amount of the boom manipulator; a slewing operation detection device 51 for detecting the operating direction and amount of the swing manipulator; a joystick operation detection device 52 for detecting the operating direction and amount of the joystick manipulator; a bucket operation detection device 53 for detecting the operating direction and amount of the bucket manipulator; pressure sensors 54a and 54b of the pumps A / B for detecting the pressure of the hydraulic pumps A / B; boom pressure sensors 55a and 55b for detecting the head / stick side load pressure of the boom cylinder 6; swing pressure sensors 56a and 56b for detecting the left / right steering load pressure of the swing motor 7; joystick pressure sensors 57a and 57b for detecting the head / stick side load pressure of the joystick cylinder 8; and bucket pressure sensors 58a and 58b for detecting the head / stick side load pressure of the bucket cylinder 9. Based on these input signals, control signals are output to the boom extension / retraction proportional solenoid valves 41a and 41b, the swing left / right steering proportional solenoid valves 42a and 42b, the joystick extension / retraction proportional solenoid valves 43a and 43b, and the bucket extension / retraction proportional solenoid valves 44a and 44b, respectively, to output pilot pressure to the pilot ports 23a, 23b to 26a and 26b on the boom, swing, joystick, and bucket direction control valves 23 to 26; the joystick flow control proportional solenoid valve 45 outputs pilot pressure to The controller 10 includes a flow control valve 28 on the secondary oil supply channel 18 of the control lever; a boom flow control proportional solenoid valve 46 that outputs pilot pressure to a boom flow control valve 29 on the secondary oil supply channel 20 of the boom; discharge proportional solenoid valves 47a and 47b that output pilot pressure to discharge valves 31 and 32; and variable capacity devices Aa and Ba of hydraulic pumps A and B, etc., to control the oil supply / discharge of the boom cylinder 6, swing motor 7, control lever cylinder 8, and bucket cylinder 9, and to control the flow rate of discharge lines E and F and the delivery flow rate of hydraulic pumps A and B. Note that the controller 10 also controls the switching of the straight travel valve 11 and the oil supply / discharge of the left / right travel motors 4 and 5, but descriptions of these controls are omitted here.

[0041] Next, a description of the control performed by controller 10 will be provided.

[0042] When detection signals are input from the respective operation detection devices 50 to 53 for the boom, swing, joystick, and bucket, the controller 10 calculates the target delivery flow rate based on the increase in the amount of operation of the controllers based on the detection signals, so as to increase the delivery flow rate of hydraulic pumps A and B, and outputs control signals to the variable capacity devices Aa and Ba of hydraulic pumps A and B so that the target delivery flow rate can be obtained. Here, the delivery flow rate of hydraulic pumps A and B is controlled individually based on hydraulic pumps A and B, which serve as the hydraulic supply source for the hydraulic actuators to be operated.

[0043] Furthermore, when detection signals are input from the respective operation detection devices 50 to 53 for the boom, swing, joystick, and bucket, the controller 10 outputs control signals to the discharge proportional solenoid valves 47a and 47b to control the discharge valves 31 and 32, so as to reduce (including reduce to zero) the discharge flow rate from hydraulic pumps A and B to the oil tank 3 according to the increase in the amount of operation of the actuator based on the detection signal. Here, the discharge flow rate of discharge lines E and F is individually controlled according to hydraulic pumps A and B, which are hydraulic supply sources operated as hydraulic actuators.

[0044] When detection signals are input from the respective operation detection devices 50 to 53 for the boom, swing, joystick, and bucket, the controller 10 calculates the target supply flow rate Qs for the boom cylinder 6, swing motor 7, joystick cylinder 8, and bucket cylinder 9 based on the operation amount of each actuator. Here, since the target operating speed of each hydraulic actuator is preset based on the operation amount of the actuator, the target supply flow rate Qs corresponding to the operation amount of the actuator is set based on the target operating speed; for each target operating speed of the boom cylinder 6 and joystick cylinder 8, which use hydraulic pumps A and B as hydraulic supply sources, a target supply flow rate Qa and Qb (Qa + Qb = Qs) is set for each hydraulic pump. When the target supply flow rates Qa and Qb of the boom / lever cylinders 6 and 8 are set, if the operating amount of the controller is less than the preset value L (which is set individually for each operating amount of the boom / lever controller), the controller 10 is set such that the total target supply flow rate Qs supplied from the hydraulic pumps A or B connected to the main side oil supply channels 17 and 22 of the boom / lever to the boom / lever cylinders 6 and 8 is only supplied by the hydraulic pump A, and no flow rate is supplied by the hydraulic pump B (Qs = Qa, Qb = 0), and the total flow rate Qs of the lever cylinder 8 is only supplied by the hydraulic pump B, and no flow rate is supplied by the hydraulic pump A (Qs = Qb, Qa = 0); if the operating amount of the controller is not less than the value L, pressurized oil is supplied from the two hydraulic pumps A and B (Qs = Qa + Qb, Qa ≠ 0, Qb ≠ 0).

[0045] Note that the controller 10 includes a target supply flow rate setting unit 60 (corresponding to the target supply flow rate setting device of the present invention), which sets target supply flow rates Qs, Qa, and Qb according to the amount of operation of the manipulator; for example, the target supply flow rate setting unit 60 has data such as a mapping indicating the relationship between the amount of operation of the manipulator and the target supply flow rates Qs, Qa, and Qb, and sets these target supply flow rates Qs, Qa, and Qb using this data; this data is incorporated into the target supply flow rate setting unit 60 as a control parameter, so that, for example, the target supply flow rate corresponding to the amount of operation of the manipulator can be changed according to the operational details of the hydraulic excavator.

[0046] The controller 10 outputs control signals for pilot pressure to the proportional solenoid valves 41a, 41b to 44a, 44b, 45, and 46 of the corresponding hydraulic actuators, thereby supplying the target supply flow rate Qs to the boom cylinder 6, swing motor 7, lever cylinder 8, and bucket cylinder 9 to control the direction control valves 23 to 26 and the flow control valves 28 and 29. Here, for the swing motor 7 and bucket cylinder 9, which use either hydraulic pump A or B as the hydraulic supply source, control signals are output to the left / right steering proportional solenoid valves 42a and 42b of the swing and the extension / retraction proportional solenoid valves 44a and 46b of the bucket, such that the supply valve passages 24e and 26e to the direction control valves 24 and 26 of the swing / bucket have an opening area corresponding to the amount of operation of their actuators. Furthermore, the supply flow rate for the slewing motor 7 and the bucket cylinder 9 is controlled by the opening area of ​​the supply valve channels 24e, 26e to the slewing / bucket direction switching valves 24, 26; and their discharge flow rate is controlled by the opening area of ​​their discharge valve channels 24f, 26f at the valve core movement position corresponding to the opening area of ​​the supply valve channels 24e, 26e.

[0047] Here, for boom / lever cylinders 6 and 8 that use two hydraulic pumps A and B as hydraulic supply sources, control signals are output to the boom / lever extension / retraction proportional solenoid valves 41a, 41b and 43a, 43b, such that the supply valve passages 23e, 25e leading to the boom / lever direction switching valves 23, 25 have an opening area corresponding to the operating amount of the actuator. Further, when the operating amount of the actuator is less than the set value L, the controller 10 outputs control signals to the boom / lever flow control proportional solenoid valves 46 and 45 to close the boom / lever flow control valves 29 and 28 located on their secondary supply passages 20 and 18; and when the operating amount of the actuator is not less than the set value L, the controller 10 outputs control signals to the boom / lever flow control proportional solenoid valves 46 and 45 to open their flow control valves 29 and 28.

[0048] Therefore, when the operating amount of the controller is less than the set value L, only the supply flow rate from hydraulic pumps A or B connected to the main side oil supply channels 17 and 22 of the boom / control lever is supplied to the boom / control lever cylinders 6 and 8; the supply flow rate to the boom / control lever cylinders 6 and 8 is controlled by the opening area of ​​the supply valve channels 23e and 25e to the boom / control lever direction switching valves 23 and 25 (supply valve channels 23e and 25e to the boom / control lever direction switching valves). The discharge / recirculation flow rate is controlled by the opening area of ​​the discharge / recirculation valve channels 23f, 25f, 23g, and 25g at the valve core movement position corresponding to the opening area of ​​the supply valve channels 23e and 25e to the boom / control lever direction switching valves 23 and 25.

[0049] When the operating amount of the controller is not less than the set value L, the total flow rate is supplied from the two hydraulic pumps A and B to the boom / lever cylinders 6 and 8. The supply flow rate to the boom / lever cylinders 6 and 8 is controlled by the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valve and the opening area of ​​its flow control valves 29 and 28. Here, the discharge / recirculation flow rate is also controlled by the opening area of ​​the discharge / recirculation valve channels 23f, 25f, 23g, and 25g at the valve core movement position corresponding to the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valves 23 and 25.

[0050] Note that the controller 10 includes a directional valve opening area setting unit 61 (corresponding to the directional valve opening area setting device of the present invention), which sets the opening area of ​​the supply / discharge valve passages 23e to 26e and 23f to 26f for the directional valves 23 to 26 according to the amount of operation of the actuator; for example, the directional valve opening area setting unit 61 has data such as a mapping indicating the relationship between the amount of operation of the actuator and the opening area (or valve core movement position) of the supply / discharge valve passages 23e to 26e and 23f to 26f for the directional valves 23 to 26, and uses the data to set the opening area; this data is incorporated into the directional valve opening area setting unit 61 as a control parameter, such that, for example, the opening area of ​​the supply / discharge valve passages 23e to 26e and 23f to 26f for the directional valves 23 to 26 can be changed according to the operating details of the hydraulic excavator based on the amount of operation of their actuators. Incidentally, the relationship between the opening areas of the supply and discharge valve passages 23e to 26e and 23f to 26f used for directional switching valves 23 to 26 is uniquely determined by the valve core movement position, and therefore cannot be changed.

[0051] In this embodiment, the boom cylinder 6 and the control lever cylinder 8 are hydraulic actuators corresponding to the high-flow hydraulic actuator of the present invention described above, and both the first and second hydraulic pumps of the present invention are used as hydraulic supply sources; the first hydraulic pump of the present invention is connected to the main side oil supply channel, and the second hydraulic pump is connected to the auxiliary side oil supply channel; when the boom cylinder 6 is used as the high-flow hydraulic actuator of the present invention, hydraulic pumps A and B become the first and second hydraulic pumps respectively, and when the control lever cylinder 8 is used as the high-flow hydraulic actuator, hydraulic pumps B and A become the first and second hydraulic pumps respectively.

[0052] As described above, when the operating amount of the actuator is not less than the set value L, the supply flow rate to the boom / lever cylinders 6 and 8 is controlled by the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valve and the opening area of ​​the boom / lever flow control valves 29 and 28; the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valve is controlled so that the opening area corresponds to the operating amount of the actuator; the opening area of ​​the boom / lever flow control valves 29 and 28 is controlled to the target opening area At calculated by the calculation unit 62 (corresponding to the calculation device of the present invention) provided on the controller 10. Here, the calculation unit 62 calculates the target opening area Af, such that the flow rate through the flow control valves 29 and 28 of the boom / lever becomes the target supply flow rate Qb and Qa of the hydraulic pumps B and A connected to the secondary oil supply channels 20 and 18 of the boom / lever on which the flow control valves 29 and 28 of the boom / lever are arranged. The calculation process is explained below, and the calculation of the target opening area Af in the flow control valves 29 and 28 of the boom and the lever is the same. Therefore, the flow control valve 28 of the lever is used as an example for calculation.

[0053] First, the calculation unit 62 uses the following formula (1) to calculate the differential pressure ΔPs before and after the flow through the supply valve channel 25e to the directional control valve of the control lever, based on the target supply flow rate Qs from the two hydraulic pumps A and B to the control lever cylinder 8 and the opening area As of the supply valve channel 25e to the directional control valve of the control lever, with the target supply flow rate Qs (Qs = Qa + Qb). Further, the calculation unit 62 uses the following formula (2) to calculate the differential pressure ΔPf before and after the flow control valve 28 of the control lever, based on the differential pressure ΔPs calculated before and after the flow control valve 28 of the control lever, and the target differential pressure ΔPc preset between the pressure of the hydraulic pump A and the load pressure of the control lever cylinder 8. Using the following formula (3), based on the differential pressure ΔPf calculated before and after the flow control valve 28 of the lever and the target supply flow rate Qa from the hydraulic pump A from the secondary oil supply channel 18 connected to the lever, the target opening area Af of the flow control valve 28 of the lever is calculated when the flow rate passes through the flow control valve 28 of the lever at the target supply flow rate Qa from the hydraulic pump A:

[0054] ΔPs={Qs / (C·As)}2…(1)

[0055] ΔPf=ΔPc-ΔPs…(2)

[0056] Af=Qa / (C·√ΔPf)…(3)

[0057] In formulas (1), (2), and (3), Qs is the target supply flow rate from the first and second hydraulic pumps A and B; Qa is the target supply flow rate from hydraulic pump A; As is the opening area from the supply valve passage 25e to the direction switching valve of the control lever; Af is the target opening area of ​​the flow control valve 28 of the control lever; ΔPc is the target differential pressure between the pressure of hydraulic pump A and the load pressure of the control lever cylinder 8; ΔPs is the differential pressure before and after the direction switching valve of the control lever from the supply valve passage 25e; ΔPf is the differential pressure before and after the flow control valve 28 of the control lever; and C is a factor.

[0058] Furthermore, formulas (1) and (3) are derived from the orifice flow formula (4) shown below:

[0059] Q=C·A·√ΔP…(4)

[0060] In formula (4), Q is the orifice velocity, A is the orifice opening area, ΔP is the orifice differential pressure, and C is a factor.

[0061] Furthermore, as described above, the target differential pressure ΔPc is a preset value of the differential pressure between the pressure of the hydraulic pump A (which is the control lever cylinder 8) and the load pressure; the relationship between the pump flow rate and the control lever operation amount and the opening area of ​​the supply valve passage 25e relative to the control lever direction switching valve are designed and coordinated to maintain the target differential pressure ΔPc. Note that the target differential pressure ΔPc can be a fixed value or a value mapped relative to the control lever operation amount, and is set in the target differential pressure setting unit 63 (equivalent to the target differential value setting device of the present invention) provided on the controller 10.

[0062] By controlling the opening area of ​​the flow control valve 28 of the joystick to maintain the calculated target opening area Af, the flow rate through the flow control valve 28 of the joystick is controlled to maintain the target supply flow rate Qa from the hydraulic pump A to the joystick cylinder 8, and the flow rate through the supply valve passage 25e to the joystick's direction switching valve is controlled to maintain the target supply flow rate Qs from both the first and second hydraulic pumps A and B to the joystick cylinder 8. By increasing or decreasing the opening area of ​​the flow control valve 28 of the joystick, even if the opening area As of the supply valve passage 25e to the joystick's direction switching valve is set according to the amount of operation of the joystick, the supply flow rate to the joystick cylinder 8 can be controlled to increase or decrease; since the discharge / recirculation flow rate from the joystick cylinder 8 is controlled by the opening area of ​​the discharge / recirculation valve passages 25f and 25g from the joystick's direction switching valve 25, the relationship between the supply, discharge, and recirculation flow rates of the joystick cylinder 8 can be changed by increasing or decreasing the opening area of ​​the flow control valve 28 of the joystick.

[0063] Next, a specific description is provided regarding the control of the joystick direction switching valve 25 and the joystick flow control valve 28 by the controller 10 when the joystick is operated separately to the extension side (joystick side).

[0064] When the joystick is operated independently to the extended side, the controller 10 sets target supply flow rates Qa and Qb from hydraulic pumps A and B to the joystick cylinder 8. Here, when the operation amount of the joystick is less than a preset value L, the target supply flow rate Qb of hydraulic pump B, connected to the main side oil supply channel 22 of the joystick, is set to increase according to the operation amount of the joystick, and the target supply flow rate Qa of hydraulic pump A, connected to the secondary side oil supply channel 18 of the joystick, is set to "zero". When the operation amount of the joystick is not less than the set value L, the target supply flow rate Qb of hydraulic pump B increases to its maximum value, and the target supply flow rate Qa of hydraulic pump A is set to increase according to the increase in the operation amount of the joystick (see [link]). Figure 3 ).

[0065] Furthermore, when the joystick is operated individually to the extended side, the controller 10 sets the opening area As of the supply valve passage 25e to the direction switching valve 25 of the joystick according to the amount of operation of the joystick. Here, the opening areas of the discharge / recirculation valve passages 25f and 25g are also set by the valve core movement position corresponding to the opening area As of the supply valve passage 25e. Furthermore, when the amount of operation of the joystick is not less than the set value L, as described above, the controller 10 calculates the target opening area Af using formulas (1), (2), and (3) so as to set the flow rate of the flow control valve 28 of the joystick provided on the secondary side oil supply passage 18 of the joystick to the target supply flow rate Qa of the hydraulic pump A.

[0066] The controller 10 outputs a control signal to the extended-side proportional solenoid valve 43a of the joystick to switch the joystick's direction switching valve 25 to the extended-side operating position X, and controls it so that the opening area of ​​the supply valve channel 25e is maintained at the preset opening area As in the extended-side operating position X. Further, the controller 10 outputs a control signal to the flow control proportional solenoid valve 45 of the joystick to control the supply flow rate from the joystick's flow control valve 28 to the joystick's direction switching valve 25; here, when the joystick's operating amount is less than the set value L, the controller 10 controls the joystick's flow control valve 28 to close, and when the joystick's operating amount is not less than the value L, the controller 10 controls the joystick's flow control valve 28 to maintain the target opening area Af above the calculated value.

[0067] Therefore, when the operating amount of the actuator is less than the set value L, pressurized oil is supplied only from hydraulic pump B to the lever cylinder 8, and its supply flow rate is controlled by the opening area As of the supply valve passage 25e to the lever's direction switching valve 25; when the operating amount of the actuator is not less than the set value L, pressurized oil is supplied from both hydraulic pumps A and B, and its supply flow rate is controlled by the opening area As of the supply valve passage 25e to the lever's direction switching valve 25 and the opening area Af of the lever's flow control valve 28. Furthermore, the discharge / recirculation flow rate of the lever cylinder 8 is controlled by the opening areas of the discharge / recirculation valve passages 25f and 25g from the lever's direction switching valve 25, respectively.

[0068] In this embodiment with the above configuration, the hydraulic control system of the hydraulic excavator includes: hydraulic pumps A and B; boom / lever cylinders 6 and 8 using these hydraulic pumps A and B as hydraulic supply sources; a swing motor 7 and a bucket cylinder 9 using either hydraulic pump A or B as hydraulic supply sources; similar control of the lever cylinder 8 will be provided as an example when controlling the supply / discharge flow rate to / from the boom / lever cylinders 6 and 8 using both hydraulic pumps A and B as hydraulic supply sources; the system is equipped with lever direction switching. Valve 25 has a supply valve passage 25e to the lever cylinder 8 and a discharge valve passage 25f from the lever cylinder 8, and switches the supply / discharge direction. The main / secondary supply passages 22 and 18 of the lever connect hydraulic pumps B and A to the pump port 25p of the lever's direction-switching valve 25, respectively. A flow control valve 28 of the lever, located at the secondary supply passage 18, controls the supply flow rate from hydraulic pump A to the lever's direction-switching valve 25. Controller 10 controls the flow rate of the lever's direction-switching valve 25 and the lever's flow... The operation of the flow control valve 28: When the operation amount of the joystick actuator is less than the set value L, by closing the flow control valve 28 of the joystick, only the flow rate from the hydraulic pump B through the main side oil supply channel 22 of the joystick is supplied to the direction switching valve 25 of the joystick; when the operation amount of the joystick actuator is not less than the value L, by opening the flow control valve 28 of the joystick, the supply flow rate from the hydraulic pump A through the secondary side oil supply channel 18 of the joystick and the supply flow rate from the hydraulic pump B through the main side oil supply channel 22 of the joystick are configured to be connected together to supply... The direction switching valve 25 of the joystick is used to control the discharge flow rate from the joystick cylinder 8 based on the opening area of ​​the discharge valve passage 25f from the direction switching valve 25 of the joystick; and when the flow control valve 28 of the joystick is closed, the supply flow rate is controlled based on the opening area of ​​the supply valve passage 25e to the direction switching valve 25 of the joystick; when the flow control valve 28 of the joystick is open, the supply flow rate is controlled based on the opening area of ​​the flow control valve 28 of the joystick and the opening area of ​​the supply valve passage 25e to the direction switching valve 25 of the joystick.The controller 10 includes a target supply flow rate setting unit 60, which sets target supply flow rates Qa and Qb from hydraulic pumps A and B to the control lever cylinder 8 based on the operation amount of the hydraulic actuator of the control lever; a directional valve opening area setting unit 61, which sets the opening area of ​​the supply / discharge valve channels 25e and 25f to / from the directional valve 25 of the control lever based on the operation amount of the control lever actuator; a target differential pressure setting unit 63, which sets the target differential pressure ΔPc between the pressure of the hydraulic pump A of the control lever cylinder 8 and the load pressure; and a calculation unit 62, which calculates the target opening area Af of the flow control valve 28 of the control lever based on the preset target supply flow rates Qa and Qb, the opening area As of the supply valve channel 25e, and the target differential pressure ΔPc, and supplies flow from the hydraulic pump A to the cylinder 8 at the target supply flow rate Qa; the controller 10 controls the operation of the flow control valve 28 of the control lever to maintain the target opening area Af calculated at the calculation unit 62.

[0069] Therefore, when the operating amount of the controller is less than the set value L, hydraulic oil is supplied from the first of hydraulic pumps A and B to the boom / control lever cylinders 6 and 8, using both pumps A and B as hydraulic supply sources; when the operating amount of the controller is not less than the value L, hydraulic oil is supplied from both hydraulic pumps A and B; when hydraulic oil is supplied from both hydraulic pumps A and B, the flow control valves 29 and 28 of the boom / control lever, based on the opening area of ​​the secondary oil supply channels 20 and 18 of the boom / control lever connected to the second of hydraulic pumps A and B, and the supply valve channels 23e and 25e to the boom / control lever... The supply flow rate is controlled by the opening area of ​​the directional control valves 23 and 25; and the discharge flow rate is controlled based on the opening area of ​​the discharge valve channels 23f and 25f of the directional control valves 23 and 25 of the boom / lever. This allows the relationship between the supply and discharge flow rates of the boom / lever cylinders 6 and 8 to be changed by increasing or decreasing the opening area of ​​the flow control valves 29 and 28 of the boom / lever, even though the relationship between the opening areas of the supply valve channels 23e and 25e and the discharge valve channels 23f and 25f to / from the directional control valves 23 and 25 of the boom / lever is unique. In areas where more hydraulic oil is supplied from two hydraulic pumps A and B (the amount of operation of the actuator is not less than the set value L), operability and work efficiency can be improved by changing the relationship between the supply and discharge flow rates. In areas where less hydraulic oil is supplied from the first of hydraulic pumps A and B (the amount of operation of the actuator is less than the set value L), the flow rate can be controlled solely by the boom / lever direction switching valves 23 and 25, which also eliminate the need for the flow control valve leading to the main side oil supply channel connected to the first of hydraulic pumps A and B and the proportional solenoid valve for pilot operation flow control valve. This helps to reduce the number of parts, simplify the circuit, and reduce costs.

[0070] Therefore, by arranging the flow control valves 29 and 28 of the boom / lever on the secondary oil supply channels 20 and 18 of the boom / lever, this embodiment can change the relationship between the supply flow rate and the discharge flow rate in areas where more hydraulic oil is supplied from the two hydraulic pumps A and B. Here, since the supply flow rate from the two hydraulic pumps A and B to the boom / lever cylinders 6 and 8 will be controlled by the opening area of ​​the flow control valves 29 and 28 of the boom / lever and the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valves 23 and 25, since no differential pressure is generated before and after the supply valve channels 23e and 25e, it is not necessary to design the opening area of ​​the supply valve channels 23e and 25e to the boom / lever direction switching valves 23 and 25 to be too large, thereby avoiding large-sized boom / lever direction switching valves 23 and 25.

[0071] Furthermore, when the supply flow rate to the boom / lever cylinders 6 and 8 is controlled by the opening areas of the flow control valves 29 and 28 of the boom / lever and the opening areas of the supply valve channels 23e and 25e to the boom / lever direction switching valves 23 and 25, the controller 10 is configured based on the target supply flow rates Qa and Qb from the hydraulic pumps A and B to the boom / lever cylinders 6 and 8; the opening areas As of the supply valve channels 23e and 25e to the boom / lever direction switching valves 23 and 25; and the hydraulic pumps B, B, and C that supply hydraulic oil to the flow control valves 29 and 28 of the boom / lever. The target differential pressure ΔPc between the pump pressure of pump A and the load pressure of boom / lever cylinders 6 and 8 is used to calculate the target opening area Af of the flow control valves 29 and 28 of the boom / lever. Therefore, the opening area of ​​the flow control valves 29 and 28 of the boom / lever can be controlled according to the target supply flow rates Qa and Qb; the opening area As of the supply valve channels 23e and 25e to the boom / lever direction switching valve; and the target differential pressure ΔPc between the pump pressure of hydraulic pumps B and A and the load pressure of boom / lever cylinders 6 and 8, so that the supply flow can be controlled with high precision.

[0072] Furthermore, when calculating the target opening area Af of the flow control valves 29 and 28 of the boom / lever, the calculation unit 62 is configured to calculate the differential pressure ΔPs before and after the boom / lever directional control valve from the supply valve channels 23e and 25e to the boom / lever directional control valve based on the target supply flow rates Qa and Qb from the hydraulic pumps A and B to the boom / lever cylinders 6 and 8 and the opening area As of the supply valve channels 23e and 25e to the boom / lever directional control valve; further, the boom / lever is calculated based on the differential pressure ΔPs calculated before and after the boom / lever directional control valve from the supply valve channels 23e and 25e to the boom / lever directional control valve and the target differential pressure ΔPc. The differential pressure ΔPf before and after the flow control valves 29 and 28 of the boom / lever is calculated; and based on the differential pressure ΔPf before and after the flow control valves 29 and 28 of the boom / lever and the target supply flow rates Qb and Qa of the hydraulic pumps B and A that supply hydraulic oil to the flow control valves 29 and 28 of the boom / lever, the target opening area Af of the flow control valves 29 and 28 of the boom / lever can be calculated. This allows the calculation of the target opening area Af of the flow control valves 29 and 28 of the boom / lever to supply flow to the hydraulic cylinders 6 and 8 of the boom / lever at the target supply flow rates Qa and Qb, which helps to improve the accuracy of the supply flow control.

[0073] Now, based on Figure 5 A description of a second embodiment of the invention is provided. The second embodiment differs from the first embodiment in the oil supply / discharge control to / from the bucket cylinder 9, and the other parts are the same as the first embodiment and have the same reference numerals; therefore, a description of it is omitted. In the first embodiment, the invention is applied to the oil supply / discharge control of a high-flow hydraulic actuator (boom / lever cylinders 6, 8) using both a first hydraulic pump and a second hydraulic pump as hydraulic supply sources; in the second embodiment, the invention is applied to the oil supply / discharge control of a hydraulic actuator (bucket cylinder 9) using a single hydraulic pump as hydraulic supply source. Furthermore, Figure 2 Shared between the first and second embodiments.

[0074] In the second embodiment, a bucket flow control valve 65 for controlling the supply flow rate from hydraulic pump A to bucket direction switching valve 26 is provided on the bucket oil supply passage 19 from hydraulic pump A to pump port 26p on bucket direction switching valve 26. The bucket flow control valve 65 is piloted by a lift valve operated by a bucket flow control proportional solenoid valve (not shown) operating based on a control signal output from controller 10, and has the same structure as the flow control valves 28 and 29 of the joystick / boom in the first embodiment.

[0075] The bucket directional control valve 26 is similar to the directional control valve in the first embodiment, including extension / retraction side pilot ports 26a, 26b; pump port 26p; tank port 26t; first and second actuator ports 26c, 26d, and is configured to switch from neutral position N to extension / retraction side operating position X or Y by pilot pressure output from extension / retraction side proportional solenoid valves 44a, 44b of the bucket, to open the supply valve passage 26e from pump port 26p to actuator port 26c or 26d and the discharge valve passage 26f from actuator port 26d or 26c to tank port 26t. The opening areas of these supply / discharge oil passages 26e and 26f are increased or decreased according to the valve core movement position moved by the pilot pressure output from the extension / retraction side proportional solenoid valves 44a and 44b of the bucket. The discharge flow rate from the bucket cylinder 9 is controlled by the opening area of ​​the discharge valve passage 26f, and the supply flow rate to the bucket cylinder 9 is controlled by the opening area of ​​the supply valve passage 26e to the bucket direction switching valve 26 and the opening area of ​​the bucket flow control valve 65 located upstream of the bucket direction switching valve 26.

[0076] When a detection signal is input from the bucket operation detection device 53, in the target supply flow rate setting unit 60, the controller 10 sets the target supply flow rate Qs of the bucket cylinder 9 according to the operation amount of the actuator. Further, in the direction switching valve opening area setting unit 61, the controller 10 sets the opening area As of the supply valve passage 26e to the bucket direction switching valve 26 according to the operation amount of the actuator, and controls the bucket direction switching valve 26 to maintain the configured opening area As. Here, the opening area of ​​the discharge valve passage 26f is also set by the valve core movement position corresponding to the opening area As of the supply valve passage 26e. Further, in the calculation unit 62, the controller 10 calculates the target opening area Af so that the bucket flow control valve 65 passes through at the target supply flow rate Qs, and controls the bucket flow control valve 65 to maintain the calculated target opening area Af.

[0077] When calculating the target opening area Af of the bucket flow control valve 65, the calculation unit 62 uses the following formula (5) to calculate the differential pressure ΔPs before and after the flow rate passes through the supply valve channel 26e to the bucket direction switching valve, based on the target supply flow rate Qs to the bucket cylinder 9 and the opening area As of the supply valve channel 26e to the bucket direction switching valve. Further, using the following formula (6), the differential pressure ΔPf is calculated before and after the bucket flow control valve 65, based on the differential pressure ΔPs calculated before and after the supply valve channel 26e to the bucket direction switching valve and the target differential pressure ΔPc preset as the target differential pressure between the pressure of the hydraulic pump A and the load pressure of the bucket cylinder 9. Furthermore, using the following formula (7), based on the calculated differential pressure ΔPf before and after the bucket flow control valve 65 and the target supply flow rate Qs to the bucket cylinder 9, the target opening area Af of the bucket flow control valve 65 is calculated when the flow rate passes through the bucket flow control valve 65 at the target supply flow rate Qs:

[0078] ΔPs={Qs / (C·As)}2…(5)

[0079] ΔPf=ΔPc-ΔPs…(6)

[0080] Af=Qs / (C·√ΔPf)…(7)

[0081] In formulas (5), (6), and (7), Qs is the target supply flow rate to the bucket cylinder 9; As is the opening area of ​​the supply valve channel 26e to the bucket direction switching valve; Af is the target opening area of ​​the bucket flow control valve 65; ΔPc is the target differential pressure between the pressure of the hydraulic pump A and the load pressure of the bucket cylinder 9; ΔPs is the differential pressure before and after the supply valve channel 26e to the bucket direction switching valve; ΔPf is the differential pressure before and after the bucket flow control valve 65; and C is a factor.

[0082] By controlling the opening area of ​​the bucket flow control valve 65 to maintain the calculated target opening area Af, the flow rate through the bucket flow control valve 65 and the supply valve passage 26e to the bucket direction switching valve is controlled to maintain the target supply flow rate Qs to the bucket cylinder 9. By increasing or decreasing the opening area of ​​the bucket flow control valve 65, even if the opening area As of the supply valve passage 26e to the bucket direction switching valve is set according to the operator's operation amount, the supply flow rate to the bucket cylinder 9 can be controlled to increase or decrease; since the discharge flow rate from the bucket cylinder 9 is controlled by the opening area of ​​the discharge valve passage 26f from the bucket direction switching valve 26, the relationship between the supply and discharge flow rates of the bucket cylinder 9 can be changed by increasing or decreasing the opening area of ​​the bucket flow control valve 65.

[0083] The second embodiment described above has supply / discharge valve channels 26e and 26f to / from the bucket cylinder 9, and a bucket flow control valve 65 is disposed upstream of the bucket direction switching valve 26 to control the supply flow rate from the hydraulic pump A to the bucket direction switching valve 26, thereby switching the supply / discharge direction. The supply flow rate to the bucket cylinder 9 is controlled based on the opening area of ​​the discharge valve channel 26f from the bucket direction switching valve 26; its supply flow rate is controlled based on the opening area of ​​the supply valve channel 26e to the bucket direction switching valve 26 and the opening area of ​​the bucket flow control valve 65; the controller 10 includes a target supply flow rate setting unit 60 for setting a target supply flow rate Qs from the hydraulic pump A to the bucket cylinder 9 according to the operation amount of the bucket operator; and a direction switching valve opening area setting unit 61 for setting the direction switching to / from the bucket according to the operation amount of the bucket operator. The opening areas of the supply / discharge valve passages 26e and 26f of the switching valve 26; the target differential pressure setting unit 63, for setting the target differential pressure ΔPc between the pressure of the hydraulic pump A of the bucket cylinder 9 and the load pressure; and the calculation unit 62, for calculating the target opening area Af of the bucket flow control valve 65 based on these target supply flow rates Qs, the opening area As of the supply valve passage 26e to the bucket direction switching valve, so as to supply the target supply flow rate Qs to the bucket cylinder 9; and the target differential pressure ΔPc, and controlling the operation of the valve 65 to maintain the target opening area Af calculated at the unit 62.

[0084] Therefore, the supply flow rate to the bucket cylinder 9 is controlled based on the opening area of ​​the supply valve channel 26e to the bucket direction switching valve 26 and the opening area of ​​the bucket flow control valve 65; even if the relationship between the opening areas of the supply / discharge valve channels 26e and 26f to / from the bucket direction switching valve 26 is uniquely determined, increasing or decreasing the opening area of ​​the bucket flow control valve 65 can also change the relationship between the supply / discharge flow rates of the bucket cylinder 9.

[0085] Therefore, in the second embodiment, the relationship between the supply and discharge flow rates for the bucket cylinder 9 can be changed by arranging the bucket flow control valve 65 upstream of the bucket direction switching valve 26; here, the supply flow rate to the bucket cylinder 9 is controlled by the opening area of ​​the supply valve channel 26e to the bucket direction switching valve 26 and the opening area of ​​the bucket flow control valve 65. Since no differential pressure is generated before and after the supply valve channel 26e, it is not necessary to design the opening area of ​​the supply valve channel 26e to the bucket direction switching valve 26 to be too large, thereby avoiding a large-sized bucket direction switching valve 26.

[0086] When the supply flow rate to the bucket cylinder 9 is controlled by the opening area of ​​the bucket directional valve 26 via the supply valve passage 26e and the opening area of ​​the bucket flow control valve 65, the controller 10 is configured to calculate the target opening area Af of the bucket flow control valve 65 based on the target supply flow rate Qs from the hydraulic pump A to the bucket cylinder 9, the opening area As of the bucket directional valve 26 via the supply valve passage 26e, and the target differential pressure ΔPc between the pressure of the hydraulic pump A and the load pressure of the bucket cylinder 9. Therefore, the opening area of ​​the bucket flow control valve 65 can be controlled according to the target supply flow rate Qs, the opening area As of the bucket directional valve 26e via the supply valve passage 26e, and the target differential pressure ΔPc between the pump pressure and the load pressure of the bucket cylinder 9, so that the supply flow rate can be controlled with high precision.

[0087] Furthermore, when calculating the target opening area Af of the bucket flow control valve 65, the calculation unit 62 is configured to calculate the differential pressure ΔPs before and after the bucket direction switching valve from the supply valve channel 26e to the bucket direction switching valve based on the target supply flow rate Qs from the hydraulic pump A to the bucket cylinder 9 and the opening area As from the supply valve channel 26e to the bucket direction switching valve; further, based on the differential pressure ΔPs calculated before and after the bucket direction switching valve from the supply valve channel 26e to the bucket direction switching valve and the target differential pressure ΔPc, the differential pressure ΔPf before and after the bucket flow control valve 65 is calculated; and based on the differential pressure ΔPf calculated before and after the bucket flow control valve 65 and the target supply flow rate Qs, the target opening area Af of the bucket flow control valve 65 is calculated; this enables the accurate calculation of the target opening area Af of the bucket flow control valve 65 for supplying the target supply flow rate Qs to the bucket cylinder 9, which helps to improve the accuracy of supply flow control.

[0088] Note that the present invention is obviously not limited to the first and second embodiments; for example, a flow control valve having the same structure as the flow control valve arranged in the secondary supply channel can be arranged in the main supply channel (in the first embodiment, the main supply channels 17, 22 of the boom / lever) that connects the first hydraulic pump to the directional valve of the high-flow hydraulic actuator. Here, by setting the flow control valve arranged in the main supply channel to be open throughout the entire operating range of the actuator, and controlling its opening area in the same way as the flow control valve arranged in the secondary supply channel, the relationship between the supply and discharge flow rates of the high-flow hydraulic actuator can be changed throughout the entire operating range.

[0089] Furthermore, when implementing the present invention, the opening area of ​​the flow control valve calculated by the computing device can be compensated by the detection value of a pressure sensor configured based on the pressure from the hydraulic pump and the load pressure of the hydraulic actuator, thereby enabling more precise control of the supply flow.

[0090] Furthermore, the present invention can obviously be implemented in various working machines with hydraulic actuators, and is not limited to hydraulic excavators.

[0091] Industrial applicability

[0092] This invention can be used in the hydraulic control system of working machinery such as hydraulic excavators.

Claims

1. A hydraulic control system, comprising a hydraulic pump and a hydraulic actuator using said hydraulic pump as a hydraulic supply source. The system includes a directional switching valve having a supply valve passage / discharge valve passage for the hydraulic actuator and switching the supply / discharge direction; a flow control valve disposed upstream of the directional switching valve for controlling the supply flow rate from the hydraulic pump to the directional switching valve; and a control device for controlling the operation of the directional switching valve and the flow control valve. The discharge flow rate for the hydraulic actuator is configured to be controlled based on the opening area of ​​the discharge valve passage from the directional switching valve, and the supply flow rate is configured to be controlled based on the opening area of ​​the supply valve passage to the directional switching valve and the opening area of ​​the flow control valve. The control device includes: a target supply flow rate setting device that sets a target supply flow rate from the hydraulic pump to the hydraulic actuator based on the operation amount of the actuator's operator; a directional switching valve opening area setting device that sets the opening area of ​​the supply valve passage / discharge valve passage for the directional switching valve based on the operation amount of the actuator's operator; a target differential pressure setting device that sets a target differential pressure between the hydraulic pump pressure and the load pressure of the hydraulic actuator; and a calculation device that calculates a target opening area of ​​the flow control valve supplying the target supply flow rate to the hydraulic actuator based on the preset target supply flow rate, the opening area of ​​the supply valve passage to the directional switching valve, and the target differential pressure; and wherein the control device controls the operation of the flow control valve to maintain the target opening area calculated by the calculation device. When calculating the target opening area of ​​the flow control valve, the calculation device calculates the differential pressure between the supply valve channel and the direction switching valve based on the target supply flow rate and the opening area between the supply valve channel and the direction switching valve; it also calculates the differential pressure before and after the flow control valve based on the differential pressure between the supply valve channel and the direction switching valve and the target differential pressure; and it calculates the target opening area of ​​the flow control valve based on the differential pressure before and after the flow control valve and the target supply flow rate.

2. The hydraulic control system according to claim 1, wherein the hydraulic control system comprises: A first hydraulic pump and a second hydraulic pump; a high-flow hydraulic actuator using both the first hydraulic pump and the second hydraulic pump as the hydraulic supply source; The directional control valve has a supply valve passage / discharge valve passage for the high-flow hydraulic actuator and switches the supply / discharge direction; a main side / sub-side oil supply passage that connects the first hydraulic pump and the second hydraulic pump to the pump port of the directional control valve, respectively; The system arrangement wherein the flow control valve is used to control the supply flow rate from the second hydraulic pump to the directional switching valve, the directional switching valve being located at the secondary supply channel; When the operating amount of the actuator of the high-flow hydraulic actuator is less than the set value, the flow control valve is closed, and only the supply flow through the main side oil supply channel is configured to be supplied from the first hydraulic pump to the directional valve; when the operating amount of the actuator of the high-flow hydraulic actuator is not less than the set value, the flow control valve is opened, and the supply flow from the second hydraulic pump through the auxiliary side oil supply channel and the supply flow from the first hydraulic pump through the main side oil supply channel are configured to be connected together to supply the directional valve. The discharge flow rate of the high-flow hydraulic actuator is configured to be controlled based on the opening area of ​​the discharge valve passage from the directional control valve; if the flow control valve is closed, the supply flow rate is configured to be controlled based on the opening area of ​​the supply valve passage to the directional control valve; and if the flow control valve is open, the supply flow rate is configured to be controlled based on the opening area of ​​the flow control valve and the opening area of ​​the supply valve passage to the directional control valve. The target supply flow rate setting device provided to the control device sets the target supply flow rate from the first hydraulic pump and the second hydraulic pump to the high-flow hydraulic actuator respectively for each of the hydraulic pumps based on the operation amount of the actuator of the high-flow hydraulic actuator; The opening area setting device of the directional switching valve sets the opening area of ​​the supply valve channel / discharge valve channel of the directional switching valve according to the operating amount of the actuator of the high-flow hydraulic actuator; the target differential pressure setting device sets the target differential pressure between the pressure of the second hydraulic pump and the load pressure of the high-flow hydraulic actuator; The computing device calculates the target opening area of ​​the flow control valve for supplying the target supply flow rate from the second hydraulic pump to the high-flow hydraulic actuator based on the preset target supply flow rate, the opening area from the supply valve channel to the direction switching valve, and the target differential pressure.

3. The hydraulic control system of claim 2, wherein when calculating the target opening area of ​​the flow control valve, the calculation device calculates the differential pressure before and after the supply valve passage to the directional control valve based on the target supply flow rate from the first hydraulic pump and the second hydraulic pump to the high-flow hydraulic actuator and the opening area of ​​the supply valve passage to the directional control valve; further calculates the differential pressure before and after the flow control valve based on the differential pressure before and after the supply valve passage to the directional control valve and the target differential pressure; and calculates the target opening area of ​​the flow control valve based on the differential pressure before and after the flow control valve and the target supply flow rate from the second hydraulic pump to the high-flow hydraulic actuator.

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