Hydraulic control system in a working machine

Abstract

To enable an electromagnetic proportional valve for outputting pilot pressure to two control valves to be shared even though the two control valves perform different operation in accordance with an operation tool operation amount.SOLUTION: Only a directional control valve for a boom is opened and a flow rate control valve for a boom is closed in the case that output pilot pressure from an electromagnetic proportional valve for a boom is less than second setting pilot pressure, and both the directional control valve for a boom and the flow rate control valve for a boom are opened in the case of being the second setting pilot pressure or more by providing a sharing electromagnetic proportional valve 41 for a boom for outputting pilot pressure in accordance with an operation tool operation amount of a boom rise side to both a directional control valve 23 for a boom and a flow rate control valve 29 for a bloom for performing supply flow rate control to a boom cylinder 8, and setting second setting pilot pressure at which a supply valve passage 29a of the flow rate control valve for a boom starts to open to pressure higher than first setting pilot pressure at which a supply valve passage 23a of the directional control valve for a boom starts to open.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Generally, in a hydraulic control system of a working machine such as a hydraulic excavator, for example, there are a first and a second hydraulic pump, a hydraulic actuator (for example, when the working machine is a hydraulic excavator, a boom cylinder for moving the boom up and down, etc.) supplied with pressure oil from both the first and the second hydraulic pumps, and first and second control valves for controlling the flow rate of the pressure oil supplied from the first and second hydraulic pumps to the hydraulic actuator, respectively. In addition, these first and second control valves are configured to be actuated by a pilot pressure output from an electromagnetic proportional valve based on the operation of an operating tool for the hydraulic actuator (for example, see Patent Document 1). In this case, dedicated electromagnetic proportional valves corresponding to the first and second control valves are used respectively. However, when electromagnetic proportional valves are provided for each control valve in this way, the number of electromagnetic proportional valves increases, and the number of drivers of the control device for outputting control signals to the electromagnetic proportional valves and the power consumption also increase, resulting in an increase in cost. In addition, the installation space for the electromagnetic proportional valves also becomes large, making it difficult to arrange the valves. Therefore, conventionally, a technique has been known in which both the first and second control valves are actuated by a pilot pressure output from a common electromagnetic proportional valve (for example, see Patent Document 2). By using a common electromagnetic proportional valve for the first and second different control valves in this way, the number of electromagnetic proportional valves can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] However, in the case of the Patent Document 2, the spools constituting the first and second control valves move simultaneously by the pilot pressure output from the electromagnetic proportional valve to the first and second control valves according to the operation amount of the operating tool, and the supply flow rate to the hydraulic actuator is controlled. For this reason, for example, as in the Patent Document 1, when the operation amount of the operating tool for the hydraulic actuator is less than the set value, one of the first and second control valves is opened and the other control valve is closed, so that pressure oil is supplied to the hydraulic actuator only from one of the first and second hydraulic pumps. On the other hand, when the operation amount of the operating tool is equal to or greater than the set value, pressure oil is supplied to the hydraulic actuator from both the first and second hydraulic pumps by opening both the first and second control valves. In such a configuration, since the first and second control valves perform different operations with respect to the operation amount of the operating tool, the technology of the Patent Document 2 cannot be adopted as it is, and this is the problem to be solved by the present invention. Means for Solving the Problems

[0005] The present invention was created for the purpose of solving these problems in view of the above circumstances. The invention of claim 1 is, first, a first hydraulic pump and a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as a hydraulic supply source, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator. In the hydraulic control system of a working machine comprising: the first and second control valves are operated by a pilot pressure output from a common electromagnetic proportional valve shared by these first and second control valves to open the supply valve paths to the hydraulic actuator, respectively. Meanwhile, the common electromagnetic proportional valve is configured to output a pilot pressure that becomes high pressure as the operation amount of the operating tool for the hydraulic actuator increases. The pilot pressure at which the second control valve starts opening the supply valve path is set to be higher than the pilot pressure at which the first control valve starts opening the supply valve path. When the operation amount of the operating tool for the hydraulic actuator is such that the pilot pressure output from the common electromagnetic proportional valve is equal to or higher than the first control valve opening start pilot pressure and less than the second control valve opening start pilot pressure, the supply valve path of the first control valve opens, but the supply valve path of the second control valve is closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. On the other hand, when the operation amount of the operating tool for the hydraulic actuator is such that the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the second control valve opening start pilot pressure, the supply valve paths of the first and second control valves open, so that the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In doing so, the second control valve is a flow control valve arranged in a sub-side supply oil passage that connects the second hydraulic pump to the pump port of the first control valve and controls the supply flow rate from the second hydraulic pump to the first control valve. The first control valve is a spool valve in which the spool moves in response to the pilot pressure output from the common electromagnetic proportional valve. In a first region, which is a spool movement region when the pilot pressure is less than the opening start pilot pressure for the second control valve, the supply pressure oil from the first hydraulic pump is supplied to the hydraulic actuator through the supply valve passage of the first control valve. On the other hand, in a second region, which is a spool movement region when the pilot pressure is equal to or greater than the opening start pilot pressure for the second control valve, the supply pressure oil from both the first and second hydraulic pumps is supplied to the hydraulic actuator through the supply valve passage of the first control valve. In a confluence start region, which is a spool movement region within a predetermined range centered on the spool movement position when the pilot pressure is equal to the opening start pilot pressure for the second control valve, the change in the opening area of the supply valve passage with respect to the pilot pressure is set to be flat A hydraulic control system for a working machine, characterized in that. Claim 2 The invention of is In a hydraulic control system of a working machine comprising a first hydraulic pump, a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as a hydraulic power source, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator, the first and second control valves are operated by a pilot pressure output from a common electromagnetic proportional valve shared by these first and second control valves to open the supply valve paths to the hydraulic actuator respectively. Meanwhile, the common electromagnetic proportional valve is configured to output a pilot pressure that becomes high pressure as the operation amount of the operating tool for the hydraulic actuator increases. Also, the pilot pressure at which the second control valve starts opening the supply valve path is set to be higher than the pilot pressure at which the first control valve starts opening the supply valve path. When the operation amount of the operating tool for the hydraulic actuator is such that the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the first control valve opening start pilot pressure and lower than the second control valve opening start pilot pressure, the supply valve path of the first control valve opens while the supply valve path of the second control valve is closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. On the other hand, when the operation amount of the operating tool for the hydraulic actuator is such that the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the second control valve opening start pilot pressure, the supply valve paths of the first and second control valves open, and the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In this regard, When the operation amount of the operating tool for the hydraulic actuator is a preset value, the pilot pressure output from the common electromagnetic proportional valve is set to the second control valve opening start pilot pressure. Meanwhile, the output pilot pressure from the common electromagnetic proportional valve is set such that the increase curve of the pilot pressure with respect to the increase in the operation amount when the operation amount of the operating tool is equal to or greater than the preset value is convex upward. A hydraulic control system for a working machine, characterized in that. Claim 3 The invention of is In a hydraulic control system for a working machine, comprising a first and a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as a hydraulic power source, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator, the first and second control valves are operated by a pilot pressure output from a common electromagnetic proportional valve shared by these first and second control valves to open the supply valve paths to the hydraulic actuator, respectively. Meanwhile, the common electromagnetic proportional valve is configured to output a pilot pressure that becomes higher as the operation amount of the operating tool for the hydraulic actuator increases. The pilot pressure at which the second control valve starts to open the supply valve path is set higher than the pilot pressure at which the first control valve starts to open the supply valve path. When the operation amount of the operating tool for the hydraulic actuator is such that the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the first control valve opening start pilot pressure and lower than the second control valve opening start pilot pressure, the supply valve path of the first control valve opens, but the supply valve path of the second control valve remains closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. When the operation amount of the operating tool for the hydraulic actuator is such that the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the second control valve opening start pilot pressure, the supply valve paths of the first and second control valves open, and the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In this configuration, The common electromagnetic proportional valve outputs a pilot pressure that increases or decreases according to the current value output from the control device based on the operation of the operating tool for the hydraulic actuator. The calibration of the current value of the common electromagnetic proportional valve is performed at two points: the current value at the start of the opening of the supply valve path of the first control valve and the current value at the start of the opening of the supply valve path of the second control valve. It is a hydraulic control system in a working machine characterized by this.

Effects of the Invention

[0006] By making the invention of claim 1, even for the first control valve and the second that perform different operations according to the operating amount of the operating tool, a common electromagnetic proportional valve that outputs a pilot pressure to operate these first and second control valves can be shared, contributing to the reduction of the electromagnetic proportional valve. control valve And by doing so, it becomes possible to ensure good operability for both fine operation and rapid operation by adjusting the timing so that the supply pressure oil from the second hydraulic pump merges with the supply pressure oil from the first hydraulic pump, and the increase ratio of the supply flow rate to the hydraulic actuator with respect to the increase in the operating amount of the operating tool becomes large. even if the confluence start position is slightly shifted due to variations in the first and second control valves or the like, the shifted amount is included in the confluence start region, and the influence of the shifted confluence start position can be reduced. Claim 2 By making the invention of, it is possible to accurately match the timing between the start of the merger of the pressure oil from the second hydraulic pump with the pressure oil from the first hydraulic pump and the start of the opening of the supply valve path of the second control valve that controls the supply flow rate from the second hydraulic pump. Claim 3 By making the invention of, it is possible to accurately match the timing between the start of the merger of the pressure oil from the second hydraulic pump with the pressure oil from the first hydraulic pump and the start of the opening of the supply valve path of the second control valve that controls the supply flow rate from the second hydraulic pump.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a hydraulic excavator 1 which is an example of a working machine provided with the hydraulic control system of the present invention. The hydraulic excavator 1 is composed of a crawler-type lower traveling body 2, an upper swing body 3 rotatably supported above the lower traveling body 2, a working device 4 mounted on the upper swing body 3, etc. Further, the working device 4 includes a boom 5 whose base end is supported by the upper swing body 3 so as to be vertically swingable, a stick 6 supported by the tip of the boom 5 so as to be swingable back and forth, and a bucket 7 swingably attached to the tip of the stick 6. The hydraulic excavator 1 is provided with boom cylinders 8, stick cylinders 9, bucket cylinders 10 for swinging the boom 5, stick 6, and bucket 7 respectively, and left and right traveling motors (not shown) for traveling the lower traveling body 2, a swing motor 11 (shown in FIG. 2) for swinging the upper swing body 3, and various hydraulic actuators.

[0009] Next, the hydraulic control system provided in the hydraulic excavator 1 will be described based on the hydraulic circuit diagram shown in FIG. 2. In FIG. 2, the hydraulic circuit of the part related to the traveling motor is omitted. In FIG. 2, A and B are variable displacement first and second hydraulic pumps, Aa and Ba are capacity variable means for varying the capacities of the first and second hydraulic pumps A and B, and 12 is an oil tank. Also, 8, 9, 10, and 11 are the boom cylinder, stick cylinder, bucket cylinder, and swing motor. In this embodiment, the boom cylinder 8 and the stick cylinder 9 use both the first and second hydraulic pumps A and B as hydraulic power sources, the bucket cylinder 10 uses the first hydraulic pump A as a hydraulic power source, and the swing motor 11 uses the second hydraulic pump B as a hydraulic power source. In this embodiment, the boom cylinder 8 corresponds to the hydraulic actuator of the present invention.

[0010] Furthermore, in FIG. 2, C is a first pump line connected to the discharge side of the first hydraulic pump A. From the first pump line C, a main supply oil passage 14 for the boom, a sub supply oil passage 15 for the stick, and a supply oil passage 16 for the bucket are branched and formed in a parallel state. Also, D is a second pump line connected to the discharge side of the second hydraulic pump B. From the second pump line D, a sub supply oil passage 17 for the boom, a supply oil passage 18 for swinging, and a main supply oil passage 19 for the stick are branched and formed in a parallel state. The main supply oil passage 14 for the boom and the sub supply oil passage 17 for the boom are oil passages connecting the first and second hydraulic pumps A and B to the pump port 23p of the boom direction switching valve 23 described later. The supply oil passage 18 for swinging is an oil passage connecting the second hydraulic pump B to the pump port 24p of the swing direction switching valve 24. The sub supply oil passage 15 for the stick and the main supply oil passage 19 for the stick are oil passages connecting the first and second hydraulic pumps A and B to the pump port 25p of the stick direction switching valve 25. The supply oil passage 16 for the bucket is an oil passage connecting the first hydraulic pump A to the pump port 26p of the bucket direction switching valve 26. In this embodiment, the main supply oil passage 14 for the boom and the sub supply oil passage 17 for the boom correspond to the main supply oil passage and the sub supply oil passage of the present invention, respectively. Also, the main supply oil passage 19 for the stick and the sub supply oil passage 15 for the stick do not correspond to the main supply oil passage and the sub supply oil passage of the present invention.

[0011] In the boom sub-side supply oil passage 17, a boom flow control valve 29 is arranged to control the supply flow rate from the second hydraulic pump B to the boom cylinder 8 and flow it to the boom direction changeover valve 23. Also, in the stick sub-side supply oil passage 15, a stick flow control valve 30 is arranged to control the supply flow rate from the first hydraulic pump A to the stick cylinder 9 and flow it to the stick direction changeover valve 25. These boom flow control valve 29 and stick flow control valve 30 are poppet valves that perform flow control by opening the supply valve passages 29a and 30a respectively by being pilot-operated by a common boom electromagnetic proportional valve 41 and a stick flow control electromagnetic proportional valve 42 (shown in FIG. 3) that operate based on a control signal output from the controller 40, and have a backflow prevention function. The flow of oil from the second hydraulic pump B to the boom direction changeover valve 23 and from the first hydraulic pump A to the stick direction changeover valve 25 is allowed, but backflow is blocked. Here, as shown in FIG. 4, the boom flow control valve 29 is set such that the supply valve passage 29a opens when the pilot pressure output from the common electromagnetic proportional valve 41 for the boom is equal to or higher than the second set pilot pressure (corresponding to the second control valve opening start pilot pressure of the present invention) Pp2, and its opening area is set to increase as the pilot pressure increases. The common electromagnetic proportional valve 41 for the boom that outputs the pilot pressure to the boom flow control valve 29 is configured to also output the pilot pressure to the extension side pilot port 23a of the boom direction switching valve 23, as will be described later. In the present embodiment, the common electromagnetic proportional valve 41 for the boom corresponds to the common electromagnetic proportional valve of the present invention, and the boom direction switching valve 23 and the boom flow control valve 29 to which the pilot pressure is supplied from the common electromagnetic proportional valve 41 for the boom correspond to the first control valve or the direction switching valve and the second control valve or the flow control valve of the present invention, respectively. Note that the setting of the pilot pressure at which the supply valve passage 29a of the boom flow control valve 29 opens can be performed, for example, by adjusting the biasing force of the spring that biases the valve body of the boom flow control valve 29 toward the supply valve passage 29a closed side. Also, in the present embodiment, the direction switching valves other than the boom direction switching valve 23 (the swing direction switching valve 24, the stick direction switching valve 25, and the bucket direction switching valve 26) do not correspond to the direction switching valve of the present invention, and the stick flow control valve 30 does not correspond to the flow control valve of the present invention.

[0012] On one hand, flow control valves such as the boom flow control valve 29 and the stick flow control valve 30 described above are not arranged in the boom main supply oil passage 14, the bucket supply oil passage 16, the slewing supply oil passage 18, and the stick main supply oil passage 19. The pressure oil from the first hydraulic pump A or the second hydraulic pump B passing through these boom main supply oil passage 14, bucket supply oil passage 16, slewing supply oil passage 18, and stick main supply oil passage 19 is directly supplied to the boom direction change valve 23, the bucket direction change valve 26, the slewing direction change valve 24, and the stick direction change valve 25 without flow control. Also, check valves 32 are arranged in these boom main supply oil passage 14, bucket supply oil passage 16, slewing supply oil passage 18, and stick main supply oil passage 19 respectively. The flow of oil from the first and second hydraulic pumps A and B to the boom direction change valve 23, the bucket direction change valve 26, the slewing direction change valve 24, and the stick direction change valve 25 is allowed, but backflow is blocked.

[0013] Thus, the pump port 23p of the boom direction change valve 23 can supply the pressure oil from the first hydraulic pump A passing through the boom main supply oil passage 14 and the pressure oil from the second hydraulic pump B passing through the boom sub supply oil passage 17. The pressure oil from the second hydraulic pump B is supplied to the boom direction change valve 23 in a state where the flow is controlled (including the shut-off state) by the boom flow control valve 29 arranged in the boom sub supply oil passage 17. Also, the pump port 25p of the stick direction change valve 25 can supply the pressure oil from the second hydraulic pump B passing through the stick main supply oil passage 19 and the pressure oil from the first hydraulic pump A passing through the stick sub supply oil passage 15. The pressure oil from the first hydraulic pump A is supplied to the stick direction change valve 25 in a state where the flow is controlled (including the shut-off state) by the stick flow control valve 30 arranged in the stick sub supply oil passage 15.

[0014] Next, the boom, slewing, stick, and bucket direction change valves 23 - 26 will be described. First, the swing and bucket direction control valves 24 and 26 that are supplied with pressure oil from either the first or second hydraulic pump A or B will be described. The swing direction control valve 24 is a closed center type spool valve that controls the supply and discharge flow rates to and from the swing motor 11 and switches the supply and discharge directions. It is connected to the left swing side and right swing side pilot proportional valves 44a and 44b (shown in FIG. 3) that output pilot pressure based on the control signal output from the controller 40, respectively. It has a left swing side pilot port 24a and a right swing side pilot port 24b, a pump port 24p connected to the swing supply oil passage 18, a tank port 24t connected to the tank line T leading to the oil tank 12, one actuator port 24c connected to the left swing side port 11a of the swing motor 11, and the other actuator port 24d connected to the right swing side port 11b of the swing motor 11. When no pilot pressure is input to both the left swing side and right swing side pilot ports 24a and 24b, the swing direction control valve 24 is in the neutral position N where it does not perform supply and discharge control for the swing motor 11. However, when pilot pressure is input to the left swing side pilot port 24a, it switches to the left swing side operating position X, opening the supply valve passage 24e from the pump port 24p to one actuator port 24c and the discharge valve passage 24f from the other actuator port 24d to the tank port 24t. Also, when pilot pressure is input to the right swing side pilot port 24b, it switches to the right swing side operating position Y, opening the supply valve passage 24e from the pump port 24p to the other actuator port 24d and the discharge valve passage 24f from one actuator port 24c to the tank port 24t. The supply flow rate and discharge flow rate to the swing motor 11 when it is in the left swing side operating position X or the right swing side operating position Y are controlled by the opening areas of the supply valve passage 24e and the discharge valve passage 24f.

[0015] The bucket direction switching valve 26 is a closed center type spool valve that controls the supply and discharge flow rates to and from the bucket cylinder 10 and switches the supply and discharge directions. It is connected to the pilot pressure output proportional solenoid valves 46a and 46b (shown in FIG. 3) for the extension side and contraction side of the bucket that output pilot pressure based on the control signal output from the controller 40, and has an extension side pilot port 26a and a contraction side pilot port 26b, a pump port 26p connected to the bucket supply oil passage 16, a tank port 26t connected to the tank line T, one actuator port 26c connected to the head side port 10a of the bucket cylinder 10, and the other actuator port 26d connected to the rod side port 10b of the bucket cylinder 10. The bucket direction switching valve 26 has the same structure as the above-described slewing direction switching valve 24, and is configured to open the supply valve passage 26e and the discharge valve passage 26f by switching from the neutral position N to the extension side operating position X and the contraction side operating position Y. The supply flow rate and discharge flow rate to the bucket cylinder 9 are controlled by the opening areas of these supply valve passage 26e and discharge valve passage 26f.

[0016] Next, the boom direction switching valve 23 and the stick direction switching valve 25, which are supplied with pressurized oil from both of the first and second hydraulic pumps A and B, will be described. The boom direction changeover valve 23 is a closed center type spool valve that controls the supply and discharge flow rates and the regeneration flow rate for the boom cylinder 8 and switches the supply and discharge directions. It includes a common electromagnetic proportional valve 41 for the boom that outputs a pilot pressure based on a control signal output from the controller 40, and pilot ports 23a and 23b on the extension side and the contraction side that are respectively connected to the boom reduction side electromagnetic proportional valve 43. A pump port 23p connected to the main supply oil passage 14 for the boom and the sub supply oil passage 17 for the boom, a tank port 23t connected to the tank line T, one actuator port 23c connected to the head side port 8a of the boom cylinder 8, and the other actuator port 23d connected to the rod side port 8b of the boom cylinder 8. When no pilot pressure is input to both the extension side and contraction side pilot ports 23a and 23b, the boom direction changeover valve 23 is in the neutral position N where it does not perform supply and discharge control for the boom cylinder 8. However, when pilot pressure is input to the extension side pilot port 23a, it switches to the extension side operating position X, opening the supply valve passage 23e from the pump port 23p to one actuator port 23c and the discharge valve passage 23f from the other actuator port 23d to the tank port 23t. Also, when pilot pressure is input to the contraction side pilot port 23b, it switches to the contraction side operating position Y, opening the supply valve passage 23e from the pump port 23p to the other actuator port 23d and the discharge valve passage 23f from one actuator port 23c to the tank port 23t, and also opening the regeneration valve passage 23g that supplies a part of the discharge oil from one actuator port 23c to the other actuator port 23d as regeneration oil. The opening areas of the supply valve passage 23e, the discharge valve passage 23f, and the regeneration valve passage 23g are controlled to increase or decrease according to the movement amount of the spool that moves by the pilot pressure output from the common electromagnetic proportional valve 41 for the boom and the boom reduction side electromagnetic proportional valve 43. The discharge flow rate and the regeneration flow rate from the boom cylinder 8 are respectively controlled by the opening areas of the discharge valve passage 23f and the regeneration valve passage 23g.In addition, regarding the supply flow rate to the boom cylinder 8, for the supply flow rate from the first hydraulic pump A to the boom cylinder 8 via the main supply oil passage 14 for the boom where no flow control valve is provided, it is controlled by the opening area of the supply valve passage 23e of the boom direction switching valve 23. On the other hand, for the supply flow rate from the second hydraulic pump B to the boom cylinder 8 via the sub supply oil passage 17 for the boom where the boom flow control valve 29 is provided, it is controlled by the opening areas of the supply valve passages 29a and 23e of the boom flow control valve 29 and the boom direction switching valve 23.

[0017] Here, the pressure oil supply from the second hydraulic pump B to the boom cylinder 8 is performed only when the boom operating tool (corresponding to the operating tool for the hydraulic actuator of the present invention) is operated by a second set value L2 or more on the boom ascending side (the extending side of the boom cylinder 8). For the operation on the boom descending side or the operation on the boom ascending side with an operation amount less than the second set value L2, the supply from the second hydraulic pump B to the boom cylinder 8 is set not to be performed. That is, when the boom operating tool is operated on the boom descending side (the contracting side of the boom cylinder 8), pilot pressure is output from the boom contracting side electromagnetic proportional valve 43 to the contracting side pilot port 23b of the boom direction switching valve 23, and the boom direction switching valve 23 switches to the contracting side operating position Y. However, as will be described later, no pilot pressure is output from the boom common electromagnetic proportional valve 41 to the boom flow control valve 29. As a result, only the pressure oil from the first hydraulic pump A is supplied to the boom direction switching valve 23 at the contracting side operating position Y, and the pressure oil from the second hydraulic pump B is not supplied. This is because when the boom descends, the high-pressure oil discharged from the head side oil chamber of the boom cylinder 8 is supplied to the rod side oil chamber via the regeneration valve passage 23g of the boom direction switching valve 23 at the contracting side operating position Y, so the pressure oil supply from the second hydraulic pump B is not required. And when it is operated on the boom descending side, the supply flow rate from the first hydraulic pump A to the boom cylinder 8 is controlled by the opening area of the supply valve passage 23e of the boom direction switching valve 23 at the contracting side operating position Y.

[0018] On the one hand, when the boom operating tool is operated on the boom ascending side, pilot pressure is output from the boom common electromagnetic proportional valve 41 to the extension side pilot port 23a of the boom direction switching valve 23 and the boom flow control valve 29. In this case, as shown in Fig. 5(A), the pilot pressure output from the boom common electromagnetic proportional valve 41 is such that when the operating tool operation amount is the first set value L1 set in advance, a pilot pressure of the first set pilot pressure Pp1 (corresponding to the first control valve opening start pilot pressure of the present invention) set in advance is output, and when the operating tool operation amount is the second set value L2 set in advance, a pilot pressure of the second set pilot pressure Pp2 is output, and the pilot pressure is controlled to increase as the operating tool operation amount on the boom ascending side increases. The first set pilot pressure Pp1 is the pilot pressure at which the supply valve path 23e of the boom direction switching valve 23 at the extension side operating position X starts to open, and the second set pilot pressure Pp2 is the pilot pressure at which the supply valve path 29a of the boom flow control valve 29 starts to open as described above, and the second set pilot pressure Pp2 is set to a higher pressure than the first set pilot pressure Pp1. When a pilot pressure equal to or higher than the first set pilot pressure Pp1 and lower than the second set pilot pressure Pp2 is output, as shown in Fig. 4, the spool of the boom direction switching valve 23 at the extension side operating position X is located in the first region V in the first half of the spool movement, and the boom flow control valve 29 is located in the dead zone region where the supply valve path 29a is maintained closed. Thus, when operated on the boom ascending side with an operation amount less than the second set value L2, only the pressure oil from the first hydraulic pump A is supplied to the supply valve path 23e of the boom direction switching valve 23 at the extension side operating position X, the pressure oil from the second hydraulic pump B is not supplied, and the supply flow rate from the first hydraulic pump A to the boom cylinder 8 is controlled by the opening area of the supply valve path 23e of the boom direction switching valve 23 at the extension side operating position X. In the present embodiment, the second set value L2 of the operating tool operation amount corresponds to the set value described in claim 4 of the present invention. Also, the first set value L1 does not correspond to the set value described in claim 4 of the present invention.

[0019] On the other hand, when the operating amount of the operating tool on the boom rising side is equal to or greater than the second set value L2, a pilot pressure equal to or greater than the second set pilot pressure Pp2 is output from the boom common electromagnetic proportional valve 41 to the extension side pilot port 23a of the boom direction switching valve 23 and the boom flow control valve 29 (see Fig. 5(A)). Then, by outputting the pilot pressure equal to or greater than the second set pilot pressure Pp2, the spool of the boom direction switching valve 23 at the extension side operating position X is located in the second region W on the latter half of the spool movement, and the supply valve path 29a of the boom flow control valve 29 is opened (see Fig. 4). Thus, when the boom is operated on the rising side with an operating amount equal to or greater than the second set value L2, pressure oil from both the first and second hydraulic pumps A and B is supplied to the supply valve path 23e of the boom direction switching valve 23 at the extension side operating position X, and the supply flow rates from the first and second hydraulic pumps A and B to the boom cylinder 8 are controlled by the opening area of the supply valve path 23e of the boom direction switching valve 23 at the extension side operating position X and the opening area of the supply valve path 29a of the boom flow control valve 29.

[0020] Here, the opening characteristics of the supply valve passage 23e of the boom direction switching valve 23 at the extended side operating position X will be described. As shown in FIG. 4, the opening area of the supply valve passage 23e increases as the pilot pressure output to the extended side pilot port 23a from the boom common electromagnetic proportional valve 41 increases. In this case, however, in the confluence start region Z, which is a predetermined range of spool movement region preset around the spool movement position when the pilot pressure is the second set pilot pressure Pp2, the opening area is set to be flat with almost no increase with respect to the increase in the pilot pressure. As described above, the second set pilot pressure Pp2 is the pilot pressure at which the supply valve passage 29a of the boom flow control valve 29 starts to open. When the pilot pressure is less than the second set pilot pressure Pp2, only the pressure oil from the first hydraulic pump A is supplied to the supply valve passage 23e. When the pilot pressure is the second set pilot pressure Pp2, the pressure oil from the second hydraulic pump B passing through the boom flow control valve 29 will confluence. In this case, even if the opening start of the boom flow control valve 29 is slightly before or after the second set pilot pressure Pp2 due to variations or the like and the confluence start position is slightly deviated, or the transition from the first region V to the second region W of the boom direction switching valve 23 is slightly deviated, the deviated portion will be included in the confluence start region Z, and the influence when the confluence start position is deviated can be reduced.

[0021] Further, as described above, the pilot pressure output from the boom common electromagnetic proportional valve 41 is controlled to increase as the operation amount of the operating tool on the boom raising side increases, and is set such that the output pilot pressure becomes the second set pilot pressure Pp2 when the operation amount of the operating tool is the second set value L2. However, the increase curve of the pilot pressure with respect to the increase in the operation amount of the operating tool when it is equal to or greater than the second set value L2 is set to be convex upward as shown in FIG. 5(A). As a result, as shown in FIG. 5(B), when the operation amount of the operating tool is less than the second set value L2, that is, when the boom cylinder 8 is supplied with pressure oil only from the first hydraulic pump A, compared to when the operation amount of the operating tool is equal to or greater than the second set value L2, that is, when the boom cylinder 8 is supplied with pressure oil from both the first and second hydraulic pumps A and B, the increase ratio of the opening area of the supply valve passage 23e of the boom direction switching valve 23 at the extension side operating position X with respect to the increase in the operation amount of the operating tool on the boom raising side is controlled to be larger. Thus, the timing is adjusted so that the pressure oil supplied from the second hydraulic pump B merges with the pressure oil supplied from the first hydraulic pump A, and the increase ratio of the supply flow rate to the boom cylinder 8 with respect to the increase in the operation amount of the operating tool becomes larger. As a result, it is possible to ensure good operability for both the fine operation of raising the boom 5 accurately by a small amount and the rapid operation of raising the boom 5 quickly.

[0022] Next, the stick direction switching valve 25 will be described. The stick direction switching valve 25 is a closed center type spool valve that controls the supply and discharge flow rates and the regeneration flow rate to and from the stick cylinder 9 and switches the supply and discharge directions. It is connected to the pilot pressure output side, extension side, and reduction side electromagnetic proportional valves 45a and 45b (shown in Fig. 3) that output pilot pressure based on the control signal output from the controller 40. It has an extension side pilot port 25a and a reduction side pilot port 25b, a pump port 25p connected to the stick main supply oil passage 19 and the stick sub supply oil passage 15, a tank port 25t connected to the tank line T, one actuator port 25c connected to the head side port 9a of the stick cylinder 9, and the other actuator port 25d connected to the rod side port 9b of the stick cylinder 9. The stick direction switching valve 25 has the same structure as the boom direction switching valve 23 described above. By switching from the neutral position N to the extension side operating position X and the reduction side operating position Y, the supply valve passage 25e and the discharge valve passage 25f are opened. Further, at the extension side operating position X, the regeneration valve passage 25g that uses a part of the discharge oil as regeneration oil is opened. Similar to the boom direction switching valve 23, the discharge flow rate and the regeneration flow rate from the stick cylinder 9 are controlled by the opening areas of the discharge valve passage 25f and the regeneration valve passage 25g, respectively. Also, the supply flow rate to the stick cylinder 9 is controlled by the opening area of the supply valve passage 25e of the stick direction switching valve 25 for the supply flow rate from the second hydraulic pump B passing through the stick main supply oil passage 19. On the other hand, for the supply flow rate from the first hydraulic pump A passing through the stick sub supply oil passage 15 where the stick flow control valve 30 is provided, it is controlled by the opening area of the supply valve passage 30a of the stick flow control valve 30 and the opening area of the supply valve passage 25e of the stick direction switching valve 25.

[0023] Here, the pressure oil supply from the first hydraulic pump A to the stick cylinder 9 is carried out only when the stick operating tool is operated to a set value LS preset on the stick-in side (the extending side of the stick cylinder 9) or the stick-out side (the contracting side of the stick cylinder 9). (The set value LS is set separately from the second set value L2 of the operating amount of the boom operating tool described above. Also, the stick-in side and the stick-out side may have the same value, but they can also be set individually. Furthermore, the set value LS, which is the operating amount of the stick operating tool, does not correspond to the set value in claim 4 of the present invention.) That is, when the stick operating tool is operated, pilot pressure is output from the stick extending side or contracting side electromagnetic proportional valves 45a, 45b to the extending side or contracting side pilot ports 25a, 25b of the stick direction switching valve 25, and the stick direction switching valve 25 switches to the extending side or contracting side operating positions X, Y. However, when the operating amount of the stick operating tool is less than the set value LS, no pilot pressure is output from the stick flow control electromagnetic proportional valve 42 to the stick flow control valve 30, and the supply valve path 30a of the stick flow control valve 30 is maintained in a closed state. As a result, only the pressure oil from the second hydraulic pump B is supplied to the stick direction switching valve 25, the pressure oil from the first hydraulic pump A is not supplied, and the supply flow rate from the second hydraulic pump B to the stick cylinder 9 is controlled by the opening area of the supply valve path 25e of the stick direction switching valve 25. On the other hand, when the operating amount of the stick operating tool is equal to or greater than the set value LS, pilot pressure is output from the stick flow control electromagnetic proportional valve 42 to the stick flow control valve 30, and thereby the supply valve path 30a of the stick flow control valve 30 opens. Thus, when the stick operating tool is operated to a value equal to or greater than the set value LS, pressure oil from both the first and second hydraulic pumps A, B is supplied to the stick direction switching valve 25, and the supply flow rates from the first and second hydraulic pumps A, B to the stick cylinder 9 are controlled by the opening areas of the supply valve paths 25e, 30a of the stick direction switching valve 25 and the stick flow control valve 30.

[0024] Furthermore, in FIG. 2, E and F are first and second bleed lines that branch off from upstream positions of all the direction control valves 23 to 26 connected to the first and second pump lines C and D and lead to the tank line T. First and second bleed valves 33 and 34 are respectively disposed in these first and second bleed lines E and F. These first and second bleed valves 33 and 34 are respectively actuated by pilot pressures output from first and second bleed electromagnetic proportional valves 47a and 47b (shown in FIG. 3) to increase or decrease the control of the bleed flow rate flowing from the first and second hydraulic pumps A and B to the oil tank 12 via the first and second bleed lines E and F. The first and second bleed electromagnetic proportional valves 47a and 47b are configured to increase or decrease the output pilot pressures to the first and second bleed valves 33 and 34 based on control signals output from the controller 40. In addition, in FIG. 2, only the boom common electromagnetic proportional valve 41 that outputs pilot pressure to the boom direction control valve 23 and the boom flow control valve 29 and the boom reduction side electromagnetic proportional valve 43 are shown among the plurality of electromagnetic proportional valves described above. Also, in FIG. 2, 35 is a pilot pump that serves as a hydraulic supply source for the pilot pressure.

[0025] On the one hand, as shown in the block diagram of FIG. 3, the controller 40 (corresponding to the control device of the present invention) includes a boom operation detection means 50 for detecting the operation direction and operation amount of the boom operation tool, a swing operation detection means 51 for detecting the operation direction and operation amount of the swing operation tool, a stick operation detection means 52 for detecting the operation direction and operation amount of the stick operation tool, a bucket operation detection means 53 for detecting the operation direction and operation amount of the bucket operation tool, a first pump pressure sensor 54 for detecting the discharge pressure of the first hydraulic pump A, a second pump pressure sensor 55 for detecting the discharge pressure of the second hydraulic pump B, boom pressure sensors 56a and 56b for detecting the load pressures on the head side and rod side of the boom cylinder 8 respectively, swing pressure sensors 57a and 57b for detecting the load pressures on the left swing side and right swing side of the swing motor 11 respectively, stick pressure sensors 58a and 58b for detecting the load pressures on the head side and rod side of the stick cylinder 9 respectively, bucket pressure sensors 59a and 59b for detecting the load pressures on the head side and rod side of the bucket cylinder 10 respectively, etc. Signals from these are input, and based on these input signals, a boom common electromagnetic proportional valve 41 that outputs pilot pressure to the extension side pilot port 23a of the boom direction switching valve 23 and the boom flow control valve 29, a stick flow control electromagnetic proportional valve 42 that outputs pilot pressure to the stick flow control valve 30, a boom reduction side electromagnetic proportional valve 43 that outputs pilot pressure to the reduction side pilot port 23b of the boom direction switching valve 23, swing left and right electromagnetic proportional valves 44a and 44b that output pilot pressure to the pilot ports 24a and 24b of the swing, stick, and bucket direction switching valves 24 to 26 respectively, stick extension and reduction side electromagnetic proportional valves 45a and 45b, bucket extension and reduction side electromagnetic proportional valves 46a and 46b, first and second bleed electromagnetic proportional valves 47a and 47b that output pilot pressure to the first and second bleed valves 33 and 34, and control signals are output to the capacity variable means Aa, Ba, etc. of the first and second hydraulic pumps A and B to perform oil supply and discharge control for the boom cylinder 8, swing motor 11, stick cylinder 9, bucket cylinder 10, flow control of the first and second bleed lines E and F, discharge flow control of the first and second hydraulic pumps A and B, etc.

[0026] Next, the control performed by the controller 40 will be described. When detection signals are input from the operation detection means 50 to 53 for the boom, slewing, stick, and bucket, the controller 40 obtains a target discharge flow rate based on these detection signals so as to increase the discharge flow rates of the first and second hydraulic pumps A and B in response to an increase in the operation amount of the operating tool, and outputs a control signal to the capacity variable means Aa and Ba of the first and second hydraulic pumps A and B so as to obtain the target discharge flow rate. In this case, the discharge flow rates of the first and second hydraulic pumps A and B are individually controlled according to the first and second hydraulic pumps A and B that are the hydraulic supply sources of the hydraulic actuators (boom cylinder 8, slewing motor 11, stick cylinder 9, bucket cylinder 10) to be operated.

[0027] Furthermore, when detection signals are input from the operation detection means 50 to 53 for the boom, slewing, stick, and bucket, the controller 40 outputs a control signal to the first and second bleed electromagnetic proportional valves 47a and 47b to control the first and second bleed valves 33 and 34 so as to decrease (including zero bleed flow rate) the bleed flow rate flowing from the first and second hydraulic pumps A and B to the oil tank 12 in response to an increase in the operation amount of the operating tool. In this case, the bleed flow rates of the first and second bleed lines E and F are individually controlled according to the first and second hydraulic pumps A and B that are the hydraulic supply sources of the operated hydraulic actuators.

[0028] Furthermore, when a detection signal is input from each of the operation detection means 50 to 53 for the boom, slewing, stick, and bucket, the controller 40 obtains the target supply flow rates for the boom cylinder 8, slewing motor 11, stick cylinder 9, and bucket cylinder 10 according to the operation amounts of the respective operation tools. Then, so that the target supply flow rates are supplied to the boom cylinder 8, slewing motor 7, stick cylinder 9, and bucket cylinder 9, control signals for pilot pressure output are output to the electromagnetic proportional valves 41 to 43, 44a, 44b to 46a, 46b for the corresponding hydraulic actuators. In this case, for the slewing motor 11 and bucket cylinder 10 that use either one of the first and second hydraulic pumps A and B as the hydraulic supply source, the supply valve paths 24e and 26e of the slewing direction changeover valve 24 and bucket direction changeover valve 26 are set to have an opening area corresponding to the target supply flow rate, and control signals are output to the left slewing side and right slewing side electromagnetic proportional valves 44a and 44b for slewing, and the extension side and contraction side electromagnetic proportional valves 46a and 46b for the bucket.

[0029] Also, regarding the boom cylinder 8 and the stick cylinder 9 that use both the first and second hydraulic pumps A and B as hydraulic power sources, the controller 40 sets the target supply flow rates from the first and second hydraulic pumps A and B for each hydraulic pump. In this case, when the boom operating tool is operated to the boom lowering side, or when the operating amount of the boom operating tool on the boom raising side and the stick operating tool is less than the second set value L2 and the set value LS described above, the total flow rate of the target supply flow rate to the boom cylinder 8 and the stick cylinder 9 is supplied from the first hydraulic pump A or the second hydraulic pump B to which the boom main supply oil passage 14 and the stick main supply oil passage 19 are connected. That is, in the case of the boom cylinder 8, the total flow rate of the target supply flow rate is supplied from the first hydraulic pump A and not supplied from the second hydraulic pump B, and in the case of the stick cylinder 9, the total flow rate of the target supply flow rate is supplied from the second hydraulic pump B and not supplied from the first hydraulic pump A. Then, control signals are output to the boom common electromagnetic proportional valve 41, the boom reducing side electromagnetic proportional valve 43, the stick extending side and reducing side electromagnetic proportional valves 45a and 45b so that the supply valve passages 23e and 25e of the boom direction switching valve 23 and the stick direction switching valve 25 have an opening area corresponding to the target supply flow rate. In this case, the pilot pressure output from the boom common electromagnetic proportional valve 41 based on the boom raising side operation is input not only to the boom direction switching valve 23 but also to the boom flow control valve 29. However, since the operating amount of the operating tool is less than the second set value L2, the output pilot pressure is less than the second set pilot pressure Pp2, and the supply valve passage 29a of the boom flow control valve 29 is maintained in a closed state. Also, when the operating amount of the stick operating tool is less than the set value LS, no control signal is output to the stick flow control electromagnetic proportional valve 42, and the supply valve passage 30a of the stick flow control valve 30 is maintained in a closed state. On one hand, when the operation amount of the boom operation tool on the boom rising side and the stick operation tool is equal to or greater than the second set value L2 and the set value LS, the shortage that cannot be satisfied by only the supply flow rates from the first hydraulic pump A connected to the main supply oil passage 14 for the boom and the second hydraulic pump B connected to the main supply oil passage 19 for the stick is supplied from the second hydraulic pump B connected to the sub supply oil passage 17 for the boom and the first hydraulic pump A connected to the sub supply oil passage 15 for the stick. Thus, the target supply flow rates for both of the first and second hydraulic pumps A and B are set respectively. Then, control signals are output to the common electromagnetic proportional valve 41 for the boom, the extension side and contraction side electromagnetic proportional valves 45a and 45b for the stick, and the electromagnetic proportional valve 42 for controlling the stick flow rate so that the opening areas of the supply valve passages 23e and 25e of the direction switching valves 23 and 25 for the boom and the supply valve passages 29a and 30a of the flow control valves 29 and 30 for the stick become the opening areas corresponding to the target supply flow rates.

[0030] Next, the pump discharge flow rate control by the controller 40, the control of the flow control valve 29 for the boom and the direction switching valve 23 for the boom, and the operations of these flow control valve 29 for the boom and direction switching valve 23 for the boom when the boom operation tool is operated alone on the boom rising side will be specifically described. First, when the boom operation tool is operated alone on the boom rising side, the controller 40 controls the discharge flow rates of the first and second hydraulic pumps A and B based on the operation amount of the operation tool. In this case, when the operation amount of the operation tool is between the first set value L1 and the second set value L2, the discharge flow rate of the first hydraulic pump A is gradually increased from the minimum flow rate in accordance with the increase in the operation amount of the operation tool so as to reach the maximum flow rate when the operation amount of the operation tool reaches the second set value L2, while the discharge flow rate of the second hydraulic pump B is maintained at the minimum flow rate. Then, when the operation amount of the operation tool is equal to or greater than the second set value L2, the discharge flow rate of the first hydraulic pump A is maintained at the maximum flow rate, while the discharge flow rate of the second hydraulic pump B is gradually increased in accordance with the increase in the operation amount of the operation tool (see Fig. 6(B)). Furthermore, when the controller 40 is operated on the boom rising side, it outputs a control signal to the common electromagnetic proportional valve 41 for the boom so as to output a pilot pressure corresponding to the operating tool operation amount. The pilot pressure from the common electromagnetic proportional valve 41 for the boom is output to the extension side pilot port 23a of the boom direction switching valve 23 and the flow control valve 29 for the boom. In this case, the controller 40 controls the common electromagnetic proportional valve 41 for the boom so as to output a pilot pressure that gradually increases in accordance with the increase in the operating tool operation amount, and controls so that the first set pilot pressure Pp1 is output when the operating tool operation amount is the first set value L1, and the second set pilot pressure Pp2 is output when the second set value L2. Then, when the pilot pressure is input to the extension side pilot port 23a of the boom direction switching valve 23, it switches to the extension side operating position X and opens the supply valve path 23e. The supply valve path 23e starts to open with the first set pilot pressure Pp1 output when the operation amount is the first set value L1, and is controlled so that the opening area increases in accordance with the increase in the pilot pressure. On the other hand, the supply valve path 29a of the flow control valve 29 for the boom is closed when the operating tool operation amount is less than the second set value L2, that is, when the pilot pressure is less than the second set pilot pressure Pp2, starts to open with the second set pilot pressure Pp2 output when the operating tool operation amount is the second set value L2, and is controlled so that the opening area increases in accordance with the increase in the pilot pressure (see Fig. 5(A)). Thus, when the operating tool operation amount on the boom rising side is less than the second set value L2, only the discharge flow rate of the first hydraulic pump A is supplied to the pump port 23p of the boom direction switching valve 23, and the supply flow rate to the boom cylinder 8 is controlled by the opening area of the supply valve path 23e of the boom direction switching valve 23. On the other hand, when the operating tool operation amount becomes the second set value L2 or more, the total flow rate of the discharge flow rate of the first hydraulic pump A and the flow rate of the second hydraulic pump B controlled by the flow control valve 29 for the boom is supplied to the pump port 25p, and the supply flow rate to the boom cylinder 8 is controlled by the opening areas of the supply valve paths 23e and 29a of the boom direction switching valve 23 and the flow control valve 29 for the boom.

[0031] Here, as described above, the boom common electromagnetic proportional valve 41 operates based on the current output from the controller 40 according to the boom raising side operation of the boom operating tool to output a pilot pressure, and the boom direction switching valve 23 and the boom flow control valve 29 operate and open by the output pilot pressure from the boom common electromagnetic proportional valve 41. When calibrating the applied current value to the boom common electromagnetic proportional valve 41, first, a first current value C1, which is the applied current value to the boom common electromagnetic proportional valve 41 when the supply valve passage 23e of the boom direction switching valve 23 at the extended side operating position X starts to open, and a second current value C2, which is the applied current value to the boom common electromagnetic proportional valve 41 when the boom flow control valve 29 starts to open, are detected. Then, when the boom raising side operation amount of the boom operating tool is at the first and second set values L1 and L2, the applied current value to the boom common electromagnetic proportional valve 41 with respect to the boom raising side operating tool operation amount is calibrated so that the first and second current values C1 and C2 are respectively applied to the boom common electromagnetic proportional valve 41. And thus, by calibrating the applied current value to the boom common electromagnetic proportional valve 41 with the two points of the first current value C1 at the start of opening of the boom direction switching valve supply valve passage 23e and the second current value C2 at the start of opening of the boom direction switching valve 23 as the calibration points CP1 and CP2, it is possible to accurately match the timing of the start of the confluence of the discharge flow rate of the first hydraulic pump A and the discharge flow rate of the second hydraulic pump B and the start of opening of the boom flow control valve 29 that controls the supply flow rate from the second hydraulic pump B. Also, when another hydraulic actuator (in this embodiment, for example, the slewing motor 11) using the second hydraulic pump B as a hydraulic supply source is operated simultaneously with the boom raising side operation and it is desired to perform control to close the boom flow control valve 29 and preferentially supply the discharge flow rate of the second hydraulic pump B to the other hydraulic actuator, by reducing the applied current value to the boom common electromagnetic proportional valve 41 to the second current value C2, it is possible to configure the boom cylinder 8 to supply pressure oil only from the first hydraulic pump A, but such control can be performed accurately.

[0032] In the present embodiment configured as described above, in the hydraulic control system of the hydraulic excavator 1, there are a first and a second hydraulic pump A, B, a boom cylinder 8 that uses both the first and second hydraulic pumps A, B as hydraulic power sources, a boom direction control valve 23 that has a supply valve passage 23e and a discharge valve passage 23f for the boom cylinder 8 and switches the supply and discharge directions, a boom main side supply oil passage 14 and a boom sub side supply oil passage 17 that connect the first and second hydraulic pumps A, B to the pump port 23p of the boom direction control valve 23 respectively, and a boom flow control valve 29 that is arranged in the boom sub side supply oil passage 17 and controls the supply flow rate from the second hydraulic pump B to the boom direction control valve 23. And the supply flow rate from the first hydraulic pump A to the boom cylinder 8 is controlled by the opening area of the supply valve passage 23e of the boom direction control valve 23, while the supply flow rate from the second hydraulic pump B to the boom cylinder 8 is controlled by the opening areas of the supply valve passages 23e, 29a of the boom direction control valve 23 and the boom flow control valve 29. And when the boom operating tool is operated to the boom ascending side, these boom direction control valve 23 and boom flow control valve 29 are actuated by the output pilot pressure from the boom common electromagnetic proportional valve 41 shared by the boom direction control valve 23 and the boom flow control valve 29 to open the supply valve passages 23e, 29a to the boom cylinder 8 respectively. In this case, the boom common electromagnetic proportional valve 41 outputs a pilot pressure that becomes high pressure as the boom ascending side operation amount of the boom operating tool increases, and the second set pilot pressure Pp2 at which the boom flow control valve 29 starts to open the supply valve passage 29a is set to a higher pressure than the first set pilot pressure Pp1 at which the boom direction control valve 23 starts to open the supply valve passage 23e.However, when the boom common electromagnetic proportional valve 41 outputs a pilot pressure that is equal to or higher than the first set pilot pressure Pp1 and lower than the second set pilot pressure Pp2, the supply valve passage 23e of the boom direction switching valve 23 opens, but the supply valve passage 29a of the boom flow control valve 29 closes. As a result, only the pressure oil from the first hydraulic pump A is supplied to the boom cylinder 8. On the other hand, when the boom common electromagnetic proportional valve 41 outputs a pilot pressure that is equal to or higher than the second set pilot pressure Pp2, the supply valve passages 23e and 29a of the boom direction switching valve 23 and the boom flow control valve 29 open, and the total flow rate from the first and second hydraulic pumps A and B is supplied to the boom cylinder 8.

[0033] In this way, in the present embodiment, when the boom operating tool is operated in the boom raising direction, by making the opening start of the supply valve passage 23e of the boom direction switching valve 23 and the supply valve passage 29a of the boom flow control valve 29 different depending on the operating tool operation amount, it is possible to supply pressure oil to the boom cylinder 8 only from the first hydraulic pump A or from both the first and second hydraulic pumps A and B according to the operating tool operation amount. In this case, as the electromagnetic proportional valve that outputs a pilot pressure to operate the boom direction switching valve 23 and the boom flow control valve 29, the boom common electromagnetic proportional valve 41 that is shared by these boom direction switching valve 23 and boom flow control valve 29 is used. And even when the boom common electromagnetic proportional valve 41 is shared by the boom direction switching valve 23 and the boom flow control valve 29 in this way, the second set pilot pressure Pp2 at which the supply valve passage 29a of the boom flow control valve 29 starts to open is set to a higher pressure than the first set pilot pressure Pp1 at which the supply valve passage 23a of the boom direction switching valve 23 starts to open. Therefore, it is possible to make the opening start of the boom direction switching valve 23 and the boom flow control valve 29 different depending on the operating tool operation amount.

[0034] As a result, even for the boom direction change valve 23 and the boom flow control valve 29 that perform different operations according to the operating amount of the operating tool on the ascending side of the boom, the common electromagnetic proportional valve 41 for the boom that outputs pilot pressure to operate these boom direction change valve 23 and boom flow control valve 29 can be shared. Thus, the number of electromagnetic proportional valves for pilot pressure output can be reduced, and the number of drivers and power consumption of the controller 40 that outputs a control signal to the common electromagnetic proportional valve 41 for the boom can also be decreased. Moreover, the installation space for the electromagnetic proportional valve can be made smaller.

[0035] Furthermore, the boom direction change valve 23 is a spool valve in which the spool moves according to the pilot pressure output from the common electromagnetic proportional valve 41 for the boom. In the first region V, which is the spool movement region when the pilot pressure is less than the second set pilot pressure Pp2, the supply pressure oil from the first hydraulic pump A is supplied to the boom cylinder 8 through the supply valve path 23e of the boom direction change valve 23. On the other hand, in the second region W, which is the spool movement region when the pilot pressure is equal to or greater than the second set pilot pressure Pp2, the supply pressure oil from both the first and second hydraulic pumps A and B is supplied to the boom cylinder 8 through the supply valve path 23e of the boom direction change valve 23. However, in the confluence start region Z, which is a preset range of spool movement region centered on the spool movement position when the pilot pressure is the second set pilot pressure Pp2, the change in the opening area of the supply valve path 23e with respect to the pilot pressure is set to be flat. Thereby, even if the start of the opening of the supply valve path 29a of the boom flow control valve 29 is slightly before or after the second set pilot pressure Pp2 due to variations or the like, and the pressure oil from the second hydraulic pump B merges with the pressure oil from the first hydraulic pump A at a confluence start position that is slightly shifted, or even if the transition from the first region V to the second region W of the boom direction change valve 23 is slightly shifted, the shifted portion is included in the confluence start region Z, and the influence when the confluence start position is shifted can be reduced.

[0036] Also, in this device, when the operation amount on the boom raising side of the boom operating tool is the second set value L2 that is preset, the pilot pressure output from the boom common electromagnetic proportional valve 41 is set to be the second set pilot pressure Pp2. On the other hand, the output pilot pressure from the boom common electromagnetic proportional valve 41 is set such that the increase curve of the pilot pressure with respect to the increase in the operation amount when the operation amount of the operating tool is equal to or greater than the second set value L2 is convex upward. Thereby, the timing is adjusted so that the supply pressure oil from the second hydraulic pump B merges with the supply pressure oil from the first hydraulic pump A, and the increase ratio of the supply flow rate to the boom cylinder 8 with respect to the increase in the operation amount of the operating tool becomes large, ensuring good operability for both the fine operation of raising the boom 5 accurately by a small amount and the rapid operation of raising the boom 5 quickly.

[0037] Furthermore, the boom common electromagnetic proportional valve 41 outputs a pilot pressure that increases or decreases according to the current value output from the controller 40 based on the boom raising side operation of the boom operating tool. When calibrating the current value of the boom common electromagnetic proportional valve 41, calibration is performed at two points, namely, the current value at the start of the opening of the supply valve path 23e of the boom direction switching valve 23 and the current value at the start of the opening of the supply valve path 29a of the boom flow control valve 29. In this way, the timing of the start of the merger of the pressure oil from the second hydraulic pump B with the pressure oil from the first hydraulic pump A and the start of the opening of the supply valve path 29a of the boom flow control valve 29 that controls the supply flow rate from the second hydraulic pump B can be accurately adjusted.

[0038] Note that the present invention is of course not limited to the above-described embodiment, and the present invention can be implemented in a hydraulic control system of various working machines equipped with a hydraulic actuator supplied with pressure oil from both the first and second hydraulic pumps. Furthermore, in the present embodiment, the first control valve has a supply valve passage and a discharge valve passage for a hydraulic actuator and is a direction control valve that switches the supply and discharge directions. A main-side supply oil passage and a sub-side supply oil passage for connecting a first hydraulic pump and a second hydraulic pump to the pump port of the first control valve are provided. The second control valve is arranged in the sub-side supply oil passage and is a flow control valve that controls the supply flow rate from the second hydraulic pump to the direction switching valve. However, the present invention is not limited thereto. For example, even if the first and second control valves are constituted by two direction switching valves respectively connected to the first and second hydraulic pumps, the present invention can be implemented.

Industrial Applicability

[0039] The present invention can be used in a hydraulic control system of a working machine including a hydraulic actuator supplied with pressure oil from both a first and a second hydraulic pump.

Explanation of Signs

[0040] 1 Hydraulic excavator 5 Boom 8 Boom cylinder 14 Main-side supply oil passage for boom 17 Sub-side supply oil passage for boom 23 Direction switching valve for boom 29 Flow control valve for boom 40 Controller 41 Common electromagnetic proportional valve for boom A First hydraulic pump B Second hydraulic pump L2 Second set value Pp1 First set pilot pressure Pp2 Second set pilot pressure

Claims

1. In a hydraulic control system for a working machine, comprising a first hydraulic pump, a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as a hydraulic power source, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator, the first and second control valves are operated by a pilot pressure output from a common electromagnetic proportional valve shared by these first and second control valves to open the supply valve paths to the hydraulic actuator, respectively. The common electromagnetic proportional valve is configured to output a pilot pressure that becomes high pressure as the operation amount of the operating tool for the hydraulic actuator increases. At the same time, the pilot pressure at which the second control valve starts to open the supply valve path is set higher than the pilot pressure at which the first control valve starts to open the supply valve path. When the operation amount of the operating tool for the hydraulic actuator outputs a pilot pressure that is equal to or higher than the first control valve opening start pilot pressure and lower than the second control valve opening start pilot pressure, the supply valve path of the first control valve opens, but the supply valve path of the second control valve remains closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. On the other hand, when the operation amount of the operating tool for the hydraulic actuator outputs a pilot pressure that is equal to or higher than the second control valve opening start pilot pressure, the supply valve paths of the first and second control valves open, so that the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In configuring this, the second control valve is a flow control valve arranged in a sub-side supply oil path connecting the second hydraulic pump to the pump port of the first control valve, and controls the supply flow rate from the second hydraulic pump to the first control valve. The first control valve is a spool valve in which the spool moves in response to the pilot pressure output from the common electromagnetic proportional valve. In a first region which is a spool movement region when the pilot pressure is less than the opening start pilot pressure for the second control valve, supply pressure oil from the first hydraulic pump is supplied to the hydraulic actuator through the supply valve path of the first control valve. On the other hand, in a second region which is a spool movement region when the pilot pressure is greater than or equal to the opening start pilot pressure for the second control valve, supply pressure oil from both the first and second hydraulic pumps is supplied to the hydraulic actuator through the supply valve path of the first control valve. In a confluence start region which is a spool movement region within a predetermined range set around the spool movement position when the pilot pressure is the opening start pilot pressure for the second control valve, the change in the opening area of the supply valve path with respect to the pilot pressure is set to be flat. A hydraulic control system for a working machine, characterized by this.

2. In a hydraulic control system for a working machine comprising a first hydraulic pump, a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as hydraulic supply sources, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator, the first and second control valves are operated by a pilot pressure output from a common electromagnetic proportional valve shared by these first and second control valves to open the supply valve paths to the hydraulic actuator respectively. The common electromagnetic proportional valve is configured to output a pilot pressure that becomes high pressure as the operation amount of the operating tool for the hydraulic actuator increases, and The pilot pressure at which the second control valve starts opening the supply valve passage is set to a higher pressure than the pilot pressure at which the first control valve starts opening the supply valve passage. When the operation amount of the operating tool for the hydraulic actuator outputs a pilot pressure that is equal to or higher than the first control valve opening start pilot pressure and lower than the second control valve opening start pilot pressure, the supply valve passage of the first control valve opens, but the supply valve passage of the second control valve remains closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. On the other hand, when the operation amount of the operating tool for the hydraulic actuator outputs a pilot pressure that is equal to or higher than the second control valve opening start pilot pressure, the supply valve passages of the first and second control valves open, and the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In forming such a configuration, When the operation amount of the operating tool for the hydraulic actuator is the preset set value, the pilot pressure output from the common electromagnetic proportional valve is set to the second control valve opening start pilot pressure. On the other hand, the output pilot pressure from the common electromagnetic proportional valve is set such that the increase curve of the pilot pressure with respect to the increase in the operation amount when the operation amount of the operating tool is equal to or greater than the set value is convex upward. A hydraulic control system for a working machine, characterized by this.

3. In a hydraulic control system for a working machine comprising a first hydraulic pump, a second hydraulic pump, a hydraulic actuator using both the first and second hydraulic pumps as a hydraulic supply source, a first control valve for controlling the supply flow rate from the first hydraulic pump to the hydraulic actuator, and a second control valve for controlling the pressure oil supply flow rate from the second hydraulic pump to the hydraulic actuator, The first and second control valves are each operated by a pilot pressure output from a common electromagnetic proportional valve shared by the first and second control valves to open the supply valve passage to the hydraulic actuator. At the same time, the common electromagnetic proportional valve is configured to output a pilot pressure that becomes a higher pressure as the operation amount of the operating tool for the hydraulic actuator increases. The pilot pressure at which the second control valve starts to open the supply valve passage is set higher than the pilot pressure at which the first control valve starts to open the supply valve passage. When the operation amount of the operating tool for the hydraulic actuator, in which the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the first control valve opening start pilot pressure and lower than the second control valve opening start pilot pressure, the supply valve passage of the first control valve opens, but the supply valve passage of the second control valve is closed, so that only the supply flow rate from the first hydraulic pump is supplied to the hydraulic actuator. On the other hand, when the operation amount of the operating tool for the hydraulic actuator, in which the common electromagnetic proportional valve outputs a pilot pressure equal to or higher than the second control valve opening start pilot pressure, the supply valve passages of the first and second control valves open, so that the total flow rate from the first and second hydraulic pumps is supplied to the hydraulic actuator. In making such a configuration, the common electromagnetic proportional valve outputs a pilot pressure that increases or decreases according to the current value output from the control device based on the operation of the operating tool for the hydraulic actuator, and the calibration of the current value of the common electromagnetic proportional valve is performed at two points, namely, the current value at the start of opening of the supply valve passage of the first control valve and the current value at the start of opening of the supply valve passage of the second control valve. A hydraulic control system for a work machine, characterized by this.

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