JP5301601B2 - Construction machinery - Google Patents

Abstract

The invention provides a construction machine which enables the pressure oil flowing out of an oil chamber on the bottom of a driven arm cylinder to be used for a hydraulic loop of a bucket arm. The construction machine includes a control execution judging part (300) and a converging control part (301). The control execution judging part (300) judges whether or not a control starting condition is established. The converging control part (301) can independently control a second movable arm flow control valve (157) to move downward with the downward movable arm operation amount. The downward position of the second flow movable arm flow control valve is provided with an oil path which enables the driven the pressure oil flowing out of the oil chamber on the bottom of the driven arm cylinder to flow to a middle bypass oil path according to the displacement of the second flow movable arm flow control valve to the downward position. When the downward movable arm operation amount is in a middle operation area, and the bucket arm operation amount to an open direction is in an upper limit operation area, the control execution judging part (300) judges that the control starting condition is established, and the converging control part makes the second flow movable arm flow control valve move to the downward position.

Description

  The present invention relates to a construction machine including a hydraulic circuit that effectively uses pressure oil flowing out from a bottom oil chamber of a boom cylinder when a boom is operated in a lowering direction.

  2. Description of the Related Art Conventionally, a boom lowering regeneration circuit that supplies pressure oil flowing out from a bottom side oil chamber of a boom cylinder to a rod side oil chamber of the boom cylinder when the boom is operated in a lowering direction is known (see, for example, Patent Document 1). .)

JP-A-10-89317

  However, since the volume of the rod-side oil chamber of the boom cylinder is smaller than the volume of the bottom-side oil chamber of the boom cylinder because the rod penetrates the oil chamber, the total amount of pressure oil flowing out from the bottom-side oil chamber is reduced. The remaining pressure oil that is not recyclable is returned to the oil tank, and it cannot be said that efficient reuse of energy is sufficiently achieved. Further, even when the pressure oil flowing out from the bottom oil chamber of the boom cylinder is supplied to other hydraulic cylinders other than the boom, the pressure oil flowing out from the bottom oil chamber of the boom cylinder depending on the working state of the construction machine. In some cases, a higher pressure than the pressure in the boom cylinder may be required, and the supply of oil passages to other hydraulic cylinders may become complicated. It was not fully planned.

  In view of the above, an object of the present invention is to provide a construction machine provided with a hydraulic circuit that makes it possible to use the pressure oil flowing out from the bottom side oil chamber of the boom cylinder to drive other hydraulic actuators.

  In order to achieve the above-described object, a construction machine according to an embodiment of the present invention is a construction machine including an attachment including an arm and a boom, and includes an arm operation amount detection unit that detects an arm operation amount, and a boom operation. A boom operation amount detection unit for detecting the amount, and a first boom flow control valve that is displaced in the raising side position direction according to the boom operation amount in the raising direction and displaced in the lower side direction according to the boom operation amount in the lowering direction A second boom flow rate control valve that is displaced in the raising-side position direction according to the amount of boom operation in the raising direction, a control execution determining unit that determines whether or not a predetermined operation is being performed by the attachment, and A control device having a merging control unit capable of controlling the displacement of the second boom flow control valve in the lower side position direction independently of the amount of boom operation in the lower direction, and below the second boom flow control valve The side position has an oil passage that joins the pressure oil flowing out from the bottom oil chamber of the boom cylinder to the center bypass oil passage according to the amount of displacement in the lower side position direction of the second boom flow control valve, When it is determined by the control execution determination unit that the boom operation amount in the lowering direction is in a predetermined intermediate operation region and the arm operation amount in the opening direction is in a predetermined upper limit operation region, The merging control unit displaces the second boom flow rate control valve to a lower side position.

  By the means described above, the present invention can provide a construction machine provided with a hydraulic circuit that makes it possible to use the pressure oil flowing out from the bottom side oil chamber of the boom cylinder to drive other hydraulic actuators.

1 is a side view showing a hydraulic excavator according to a first embodiment. It is the schematic which shows the structural example of the hydraulic circuit mounted in the hydraulic shovel which concerns on a 1st Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on a 1st Example. It is a flowchart which shows the flow of the confluence | merging control process performed with the hydraulic shovel which concerns on a 1st Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on a 2nd Example. It is the schematic which shows the structural example of the hydraulic circuit mounted in the hydraulic shovel which concerns on a 3rd Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on a 3rd Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on 4th Example. It is the schematic which shows the structural example of the hydraulic circuit mounted in the hydraulic shovel which concerns on 5th Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on 5th Example. It is a flowchart which shows the flow of the control execution determination process performed with the hydraulic shovel which concerns on 6th Example.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a side view showing a hydraulic excavator according to a first embodiment of the present invention. The hydraulic excavator mounts an upper swing body 3 on a crawler type lower traveling body 1 via a swing mechanism 2 so as to be rotatable.

  The upper swing body 3 is equipped with a drilling attachment including a boom 4, an arm 5, and a bucket 6 and a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 that drive each of them in the front center portion. . In addition, the upper swing body 3 has a cabin 10 for an operator to get on, and an engine (not shown) as a drive source on the rear. In the following, the boom cylinder 7, the arm cylinder 8, the bucket cylinder 9, the traveling hydraulic motor (not shown), the turning hydraulic motor (not shown), etc. are collectively referred to as “hydraulic actuator”. And

  FIG. 2 is a schematic diagram illustrating a configuration example of a hydraulic circuit mounted on the hydraulic excavator according to the first embodiment. In FIG. 2, the high-pressure oil passage, the pilot oil passage, and the electric drive / control system are indicated by a solid line, a broken line, and a dotted line, respectively.

  In the first embodiment, the hydraulic circuit circulates the pressure oil from the two main pumps 12L and 12R driven by the engine through the center bypass oil passages 40L and 40R to the oil tank.

  The main pumps 12L and 12R are devices for supplying pressure oil to the control valve 150 and the flow rate control valves 151 to 160 via high-pressure oil passages, and are, for example, swash plate type variable displacement hydraulic pumps. Note that negative control control is preferably employed for the pump control system of the main pumps 12L and 12R.

  The regulators 13L and 13R are devices for controlling the discharge amounts of the main pumps 12L and 12R. For example, the discharge amounts of the main pumps 12L and 12R are adjusted by adjusting the swash plate tilt angles of the main pumps 12L and 12R. To control.

  The center bypass oil passage 40L is a high-pressure oil passage that communicates the flow control valves 151, 153, 155, 157, and 158, and includes a negative control throttle 20L between the flow control valve 159 and the pressure oil tank that are located on the most downstream side. .

  The center bypass oil passage 40R is a high-pressure oil passage that communicates the control valve 150 and the flow control valves 152, 154, 156, 159, and 160, and is negative between the most downstream flow control valve 160 and the pressure oil tank. A control aperture 20R is provided.

  The flow of pressure oil discharged from the main pumps 12L and 12R is limited by the negative control throttles 20L and 20R. Therefore, the negative control throttles 20L and 20R generate control pressure (hereinafter referred to as “negative control pressure”) for controlling the regulators 13L and 13R.

  The negative control pressure oil passages 41L and 41R are pilot oil passages for transmitting the negative control pressure generated upstream of the negative control throttles 20L and 20R to the regulators 13L and 13R.

  The regulators 13L and 13R control the discharge amounts of the main pumps 12L and 12R by adjusting the swash plate tilt angles of the main pumps 12L and 12R according to the negative control pressure. Further, the regulators 13L and 13R decrease the discharge amount of the main pumps 12L and 12R as the introduced negative control pressure increases, and increase the discharge amounts of the main pumps 12L and 12R as the introduced negative control pressure decreases. .

  Specifically, when none of the hydraulic actuators in the hydraulic excavator is operated (hereinafter referred to as “standby mode”), the pressure oil discharged from the main pumps 12L and 12R passes through the center bypass oil passages 40L and 40R. Through the negative control apertures 20L and 20R. The flow of pressure oil discharged from the main pumps 12L and 12R increases the negative control pressure generated upstream of the negative control throttles 20L and 20R. As a result, the regulators 13L and 13R reduce the discharge amount of the main pumps 12L and 12R to the allowable minimum discharge amount, and the pressure loss (pumping loss) when the discharged pressure oil passes through the center bypass oil passages 40L and 40R. Try to suppress.

  On the other hand, when any hydraulic actuator in the hydraulic excavator is operated, the pressure oil discharged from the main pumps 12L and 12R flows into the operation target hydraulic actuator via the flow control valve corresponding to the operation target hydraulic actuator. . The flow of pressure oil discharged from the main pumps 12L and 12R reduces or eliminates the amount reaching the negative control throttles 20L and 20R, and lowers the negative control pressure generated upstream of the negative control throttles 20L and 20R. As a result, the regulators 13L and 13R receiving the reduced negative control pressure increase the discharge amount of the main pumps 12L and 12R, circulate sufficient pressure oil to the operation target hydraulic actuator, and ensure that the operation target hydraulic actuator is driven. It shall be

  With the configuration as described above, in the standby mode, the hydraulic system in FIG. 2 consumes unnecessary energy in the main pumps 12L and 12R (pressure oil discharged from the main pumps 12L and 12R is generated in the center bypass oil passages 40L and 40R. Pumping loss).

  In addition, when the hydraulic actuator is driven, the hydraulic system of FIG. 2 can reliably supply necessary and sufficient pressure oil from the main pumps 12L and 12R to the hydraulic actuator to be driven.

  Further, in addition to the negative control pressure control described above, the regulators 13L and 13R adjust the swash plate tilt angle of the main pumps 12L and 12R according to the discharge pressure of the main pumps 12L and 12R (by total horsepower control). It is assumed that the discharge amounts of the main pumps 12L and 12R are controlled. Specifically, the regulators 13L and 13R reduce the discharge amount by adjusting the swash plate tilt angle of the main pumps 12L and 12R when the discharge pressure of the main pumps 12L and 12R exceeds a predetermined value. The pump horsepower represented by the product of the pressure and the discharge amount should not exceed the engine output horsepower.

  The control valve 150 is a traveling straight valve, and is a spool valve that operates when left and right traveling hydraulic motors (not shown) that drive the lower traveling body 2 and other hydraulic actuators are operated simultaneously. It is. Specifically, the control valve 150 switches the flow of the pressure oil so as to circulate the pressure oil only from the main pump 12L to each of the flow control valve 151 and the flow control valve 152 in order to improve the straight traveling performance of the lower traveling body 2. be able to.

  The flow rate control valve 151 is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged from the main pump 12L by a left-side traveling hydraulic motor (not shown), and the flow rate control valve 152 is a main pump. This is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged by 12L or 12R with a right-side traveling hydraulic motor (not shown).

  The flow rate control valve 153 is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged from the main pump 12L or 12R with a turning hydraulic motor (not shown).

  The flow rate control valve 154 is a spool valve for supplying the pressure oil discharged from the main pump 12R to the bucket cylinder 9 and discharging the pressure oil in the bucket cylinder 9 to the oil tank.

  The flow control valve 155 is a spare spool valve that can be used to drive a hydraulic motor or a hydraulic cylinder.

  The flow rate control valves 156 and 157 supply pressure oil discharged from the main pumps 12L and 12R to the boom cylinder 7, and spools for switching the flow of pressure oil to discharge the pressure oil in the boom cylinder 7 to the oil tank. It is a valve. The flow control valve 156 is a spool valve (hereinafter referred to as a “first boom flow control valve”) that always operates when the boom operation lever 16B is operated. The flow control valve 157 is a spool valve (hereinafter referred to as “second boom flow control valve”) that operates only when the boom operation lever 16B is operated at a predetermined lever operation amount or more.

  The first boom flow rate control valve 156 includes a high-pressure oil passage 156A including a check valve between the CT port and the PC port at the lowered position (the spool position on the right side in the figure). The CT port is a port connecting the bottom oil chamber of the boom cylinder 7 and the oil tank, the PC port is a port connecting the main pump 12R and the rod side oil chamber of the boom cylinder 7, and the PT port is The port connecting the main pump 12R and the oil tank. The high-pressure oil passage 156 </ b> A is a regeneration high-pressure oil passage for allowing the pressure oil flowing out from the bottom-side oil chamber of the boom cylinder 7 to flow into the rod-side oil chamber of the boom cylinder 7. Further, the opening area of the regeneration high-pressure oil passage 156A is proportional to the amount of displacement of the first boom flow control valve 156 in the lower side position direction (left direction in the figure).

  The second boom flow rate control valve 157 includes a high-pressure oil passage 157A including a check valve and a throttle between the PT port and the bottom-side oil chamber of the boom cylinder 7 at the lowered position (the left spool position in the figure). . The high pressure oil passage 157A is a joining high pressure oil passage for joining the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 to the center bypass oil passage 40L. The opening area of the merging high-pressure oil passage 157A is proportional to the amount of displacement of the second boom flow rate control valve 157 in the lower side position direction (right direction in the figure).

  The flow rate control valves 158 and 159 are spools for supplying pressure oil discharged from the main pumps 12L and 12R to the arm cylinder 8 and switching the flow of pressure oil in order to discharge the pressure oil in the arm cylinder 8 to the oil tank. It is a valve. The flow control valve 158 is a valve that is always operated when the arm operation lever 16A is operated (hereinafter referred to as a “first arm flow control valve”). The flow control valve 159 is a valve that operates only when the arm operation lever 16A is operated at a predetermined lever operation amount or more (hereinafter referred to as a “second arm flow control valve”).

  The flow rate control valve 160 is a spool valve that switches whether or not the pressure oil discharged from the main pump 12R reaches the negative control throttle 20R.

  The arm operating lever 16A is an operating device for operating the arm 5 and uses the pressure oil discharged from a control pump (not shown) to change the pilot pressure corresponding to the lever operating amount to the first arm flow rate. The control valve 158 and the second arm flow control valve 159 are introduced into either the left or right pilot port.

  The boom operation lever 16B is an operation device for operating the boom 4, and uses the pressure oil discharged from the control pump to apply a pilot pressure corresponding to the lever operation amount to the first boom flow control valve 156 and the second boom flow control valve 156. The boom flow rate control valve 157 is introduced into either the left or right pilot port.

  The bucket operating lever 16C is an operating device for operating the bucket 6 and uses the pressure oil discharged from the control pump to apply a pilot pressure corresponding to the lever operating amount to either the left or right pilot of the flow control valve 154. Let the port introduce.

  The arm opening pilot pressure sensor 17A is an example of an arm operation amount detection unit, and is a pressure sensor that detects a lever operation amount (lever operation angle) in the opening direction of the arm operation lever 16A as a pressure, and the detected value is a controller. 30 is output.

  The boom lowering pilot pressure sensor 17B is an example of a boom operation amount detection unit, and is a pressure sensor that detects a lever operation amount (lever operation angle) in the lowering direction of the boom operation lever 16B as a pressure, and the detected value is a controller. 30 is output.

  The bucket opening pilot pressure sensor 17C is an example of a bucket operation amount detection unit, and is a pressure sensor that detects a lever operation amount (lever operation angle) in the opening direction of the bucket operation lever 16C as a pressure, and the detected value is a controller. 30 is output.

  The left and right traveling levers (or pedals) and the turning operation lever (both not shown) are operation devices for operating the traveling of the lower traveling body 2 and the turning of the upper revolving body 3, respectively. As with the arm operation lever 16A and the like, these operation devices use the pressure oil discharged from the control pump to change the pilot pressure corresponding to the lever operation amount (or pedal operation amount) to the left and right traveling hydraulic motors and the swivel. It is introduced into either the left or right pilot port of the flow control valve corresponding to each hydraulic motor. Further, the operator's operation contents (the lever operation direction and the lever operation amount) for each of these operation devices are detected in the form of pressure by the corresponding pressure sensors in the same manner as the pressure sensors 17A to 17C. The value is output to the controller 30.

  The main relief valve 18 is a safety valve that discharges the pressure oil to the oil tank and controls the discharge pressure to be lower than the predetermined relief pressure when the discharge pressure of the main pump 12L or 12R becomes equal to or higher than the predetermined relief pressure.

  The relief valves 19L and 19R are safety valves that control the negative control pressure to be less than the predetermined relief pressure by discharging the pressure oil to the oil tank when the negative control pressure upstream of the negative control throttles 20L and 20R exceeds a predetermined relief pressure. It is.

  The proportional solenoid valve 21 is a device for controlling the pilot pressure acting on the pilot port on the lower side (left side) of the second boom flow rate control valve 157. For example, the proportional solenoid valve 21 outputs the output pressure according to the control command current from the controller 30. Is a proportional electromagnetic pressure reducing valve.

  The controller 30 is a control device for controlling the hydraulic circuit, and includes, for example, a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like.

  In addition, the controller 30 reads a program corresponding to each of the control execution determination unit 300 and the merge control unit 301 from a non-volatile storage medium such as a ROM and develops the program on a volatile storage medium such as a RAM, and processes corresponding thereto Is executed by the CPU.

  Specifically, the controller 30 receives detection values output from the pressure sensors 17A to 17C and the like, and executes processes by the control execution determination unit 300 and the merge control unit 301 based on the detection values.

  Thereafter, the controller 30 appropriately outputs a control command current corresponding to the processing results of the control execution determination unit 300 and the merging control unit 301 to the proportional solenoid valve 21.

  The control execution determination unit 300 performs an operation such as a soil removal operation using a digging attachment or a horizontal return operation that moves the arm 5 in the opening direction while operating the boom 4 in the downward direction in the air (hereinafter referred to as “a soil removal operation or the like”). ").) Is a functional element for determining whether or not to perform displacement control of the second boom flow rate control valve 157 to the lower side position by the merge control unit 301, for example, an arm operation lever It is determined whether the control start condition is satisfied (whether the control release condition is not satisfied) based on the lever operation amount in the opening direction of 16A and the lever operation amount in the downward direction of the boom operation lever 16B. .

  Specifically, in the control execution determination unit 300, the lever operation amount in the opening direction of the arm operation lever 16A is in a predetermined upper limit side operation region, and the lever operation amount in the lowering direction of the boom operation lever 16B is a predetermined intermediate value. When it is in the operation region or the upper limit side operation region, it is determined that the control start condition is satisfied (in the state of earth removal work or the like).

  The “upper limit side operation area” means a range of lever operation amounts when the operation lever is operated to near the maximum lever operation angle in order to operate the operation target in a desired operation direction. For example, the upper limit side operation area includes the lever operation amount of the arm operation lever 16A when the arm operation lever 16A is fully operated to operate the arm 5 in the opening direction.

  The “intermediate operation area” means a range of lever operation amounts when the operation lever is operated in order to slowly operate the operation target in a desired operation direction. For example, the intermediate operation region includes a lever operation amount of the boom operation lever 16B when the boom operation lever 16B is operated in order to slowly operate the boom 4 in the downward direction.

  More specifically, the intermediate operation region is a boom operation for operating the boom 4 in the downward direction while operating the arm 5 in the opening direction in the air in operations such as discharging soil and sand to a predetermined place, leveling operation, etc. It includes the lever operation amount of the boom operation lever 16B when the lever 16B is operated.

  Further, the upper limit side operation area may be set such that the lower limit thereof is the same as the upper limit of the intermediate operation area, and is set so as to leave a certain interval between the lower limit and the upper limit of the intermediate operation area. Also good.

  The merge control unit 301 is a functional element for controlling the displacement of the second boom flow rate control valve 157 in the lower side position direction (right direction in FIG. 2).

  Specifically, the merging control unit 301 is, for example, a pilot that acts on the pilot port on the lower side (left side) of the second boom flow control valve 157 independently of the lever operation amount in the lowering direction of the boom operation lever 16B. The pressure is controlled, and the amount of displacement of the second boom flow rate control valve 157 in the lower side position direction (right direction in FIG. 2) is controlled. The amount of displacement of the second boom flow rate control valve 157 in the lower side position direction (right direction in FIG. 2) is the magnitude of the pilot pressure acting on the lower side (left side) pilot port of the second boom flow rate control valve 157. It is proportional to the height.

  More specifically, the merge control unit 301 controls the control command current for the proportional solenoid valve 21 when the control execution determination unit 300 determines that the control start condition is not satisfied (control release condition is satisfied), for example. And the communication between the lower pilot pressure oil passage of the second boom flow control valve 157 and the lower pilot pressure oil passage of the boom operation lever 16B is cut off, and the second boom flow control valve 157 Connect the pilot port on the lower side (left side) to the drain (oil tank) port. Thereby, the merging control unit 301 prohibits the second boom flow rate control valve 157 from being displaced in the lower side position direction (right direction in FIG. 2), and the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 is centered. It is prohibited to join the bypass oil passage 40L. In the present embodiment, the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 is the high pressure oil passage 156A for regeneration of the first boom flow control valve 156 while the boom operation lever 16B is operated in the downward direction. To the rod-side oil chamber of the boom cylinder 7.

  On the other hand, the merge control unit 301 outputs a control command current having a predetermined magnitude to the proportional solenoid valve 21 when the control execution determination unit 300 determines that the control start condition is satisfied, for example, The pressure oil in the lower pilot pressure oil passage of the lever 16B is adjusted to a pressure corresponding to the control command current and introduced into the lower (left side) pilot port of the second boom flow control valve 157. Note that the boom lowering pilot pressure tends to increase with an increase in the lever operation amount in the lowering direction of the boom operation lever 16B. Thereby, the merging control unit 301 displaces the second boom flow rate control valve 157 in the lower side position direction (right direction in FIG. 2), and the center bypass oil passage for the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7. Start merging to 40L. In this embodiment, the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 is also regenerated in the rod side oil chamber of the boom cylinder 7. The boom lowering pilot pressure acting on the lower-side (left side) pilot port of the second boom flow control valve 157 is preferably a preset constant value (typically a higher value). It is controlled to become. In this embodiment, the boom lowering pilot pressure acting on the lower side (left side) pilot port of the second boom flow rate control valve 157 is set to the lower side of the boom operating lever 16B in consideration of the open failure of the proportional solenoid valve 21. Although the pressure oil in the pilot pressure oil passage is used as the original pressure, the pressure oil discharged from a control pump (not shown) may be used as the original pressure. In this case, the proportional solenoid valve 21 may be a proportional solenoid valve instead of a proportional solenoid pressure reducing valve.

  Further, the merging control unit 301 changes the boom lowering pilot pressure acting on the lower pilot port of the second boom flow rate control valve 157 according to the pressure of the bottom side oil chamber of the boom cylinder 7, and the second boom flow rate. The amount of displacement of the control valve 157 in the lower side position direction may be changed.

  In addition, the merging control unit 301 changes the boom lowering pilot pressure acting on the lower pilot port of the second boom flow control valve 157 according to the lever operation amount in the lowering direction of the boom operating lever 16B. The amount of displacement of the flow control valve 157 in the lower side position direction may be changed. In this case, the merging control unit 301 acts on the lower pilot port of the second boom flow control valve 157 so as to be different from the boom lowering pilot pressure acting on the lower pilot port of the first boom flow control valve 156. The boom lowering pilot pressure may be changed.

  Further, the merging control unit 301 displaces the second boom flow control valve 157 toward the lower side position in accordance with the pressure in the bottom side oil chamber of the boom cylinder 7 and the lever operation amount in the lowering direction of the boom operation lever 16B. The amount may be changed.

  In addition, the merging control unit 301 includes a second boom flow control valve according to the current setting content of the construction machine, such as the operation mode of the construction machine (for example, H mode, SP mode, etc.), the target engine speed, and the like. The boom lowering pilot pressure acting on the lower pilot port 157 may be changed.

  In addition, the merge control unit 301 is a pilot port on the lower side of the second boom flow control valve 157 in response to an operator input via an input device (not shown) such as a touch panel installed in the cabin 10. The boom lowering pilot pressure may be effective. On the contrary, the action of the boom lowering pilot pressure on the lower pilot port of the second boom flow control valve 157 may be invalidated.

  Further, the boom lowering pilot pressure acting on the lower side (left side) pilot port of the second boom flow rate control valve 157 may be controlled to change stepwise, and may change linearly or nonlinearly steplessly. It may be controlled.

  In addition, when the control execution determination unit 300 determines that the control start condition is satisfied, the merging control unit 301 determines that the control start condition is not satisfied again (the control release condition is satisfied). The communication between the pilot port on the lower side (left side) of the second boom flow control valve 157 and the lower pilot pressure oil passage of the boom operation lever 16B is blocked, and the lower side of the second boom flow control valve 157 ( The pilot port on the left side is communicated with the drain (oil tank) port so that the pilot pressure acting on the pilot port on the lower side (left side) of the second boom flow rate control valve 157 is returned to the state before the change.

  Here, with reference to FIG. 3, the control execution determination unit 300 executes displacement control of the second boom flow rate control valve 157 to the lower side position by the merging control unit 301 at the time of soil removal work or the like by the excavation attachment. An example of processing for determining whether or not (hereinafter referred to as “control execution determination processing”) will be described. FIG. 3 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the first embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be. It is assumed that the initial value of the control determination flag F (initialization processing set value when the controller 30 is activated) is “0”.

  First, in the control execution determination unit 300, the lever operation amount in the opening direction of the arm operation lever 16A is in the upper limit side operation region, and the lever operation amount in the lowering direction of the boom operation lever 16B is in the intermediate operation region or the upper limit side operation. It is determined whether it is in the area.

  Specifically, control execution determination unit 300 determines whether or not the boom lowering pilot pressure, which is the output of boom lowering pilot pressure sensor 17B, is equal to or higher than a predetermined threshold value β (step ST1). In this case, the boom lowering pilot pressure being equal to or greater than the predetermined threshold value β means that the lever operation amount in the raising direction of the boom operation lever 16B is in the intermediate operation area or the upper limit operation area.

  When it is determined that the boom lowering pilot pressure is equal to or higher than the threshold value β (YES in step ST1), the control execution determining unit 300 has an arm opening pilot pressure that is an output of the arm opening pilot pressure sensor 17A is equal to or higher than a predetermined threshold value α. Is determined (step ST2). In this case, the arm opening pilot pressure being equal to or greater than the predetermined threshold value α means that the lever operation amount in the opening direction of the arm operation lever 16A is in the upper limit side operation region.

  When it is determined that the arm opening pilot pressure is greater than or equal to the threshold value α (YES in step ST2), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” to the control determination flag F ( Step ST3).

  On the other hand, when it is determined that the boom lowering pilot pressure is less than the threshold value β (NO in step ST1), the control execution determination unit 300 determines that the control start condition is not satisfied (the control release condition is satisfied). “0” is set to the control determination flag F (step ST4). This is because it can be determined that the lever operation amount in the lowering direction of the boom operation lever 16B is not in either the intermediate operation region or the upper limit side operation region.

  Further, even when it is determined that the boom lowering pilot pressure is equal to or higher than the threshold value β, when it is determined that the arm opening pilot pressure is lower than the threshold value α (NO in step ST2), the control execution determining unit 300 Then, it is determined that the control start condition is not satisfied (control release condition is satisfied), and the control determination flag F is set to “0” (step ST4). This is because it can be determined that the lever operation amount in the opening direction of the arm operation lever 16A is not in the upper limit side operation region.

  The control execution determination unit 300 determines whether the boom lowering pilot pressure is equal to or higher than the threshold value β after determining whether the arm opening pilot pressure is equal to or higher than the threshold value α. Alternatively, these determinations may be made at the same time. The same applies to other embodiments described below.

  Next, an example of a process in which the merging control unit 301 displaces the second boom flow rate control valve 157 (hereinafter referred to as “merging control process”) will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the merge control process, and this merge control process is executed continuously while the hydraulic excavator is operating.

  First, the merging control unit 301 reads the control determination flag F set in the control execution determination process (step ST11), and determines whether the control determination flag F is “1” or “0” (step ST11). ST12).

  When it is determined that the control determination flag F is “1” (YES in step ST12), the merging control unit 301 executes merging control (step ST13) and displaces the second boom flow control valve 157 to the lower side position. Let

  Specifically, the merging control unit 301 reduces the control command current for the proportional solenoid valve 21 from a maximum value to a predetermined magnitude, and operates the pilot port on the lower side (left side) of the second boom flow rate control valve 157 to operate the boom. The lever 16B communicates with the lower pilot pressure oil passage. This is because the pressure oil in the lower pilot pressure oil passage of the boom operation lever 16B is adjusted to a pressure corresponding to the control command current and introduced to the lower (left side) pilot port of the second boom flow control valve 157. When the second boom flow rate control valve 157 is already in the desired lower side position, the merge control unit 301 maintains the second boom flow rate control valve 157 in the desired lower side position.

  On the other hand, when it is determined that the control determination flag F is not “1” (“0”) (NO in step ST12), the merging control unit 301 cancels the merging control (step ST14), and the second boom flow rate control is performed. The valve 157 is displaced to the neutral position (spool position at the center in the figure).

  Specifically, the merge control unit 301 maximizes the magnitude of the control command current for the proportional solenoid valve 21, and lowers the pilot port on the lower side (left side) of the second boom flow rate control valve 157 and the lower side of the boom operation lever 16B. The communication with the pilot pressure oil passage is shut off, and the lower (left side) pilot port of the second boom flow rate control valve 157 is communicated with the drain (oil tank) port. When the second boom flow control valve 157 is already in the neutral position, the merge control unit 301 maintains the second boom flow control valve 157 in the neutral position.

  With the above configuration, the hydraulic excavator according to the first embodiment is limited to the case where it is determined that the displacement control to the lower side position of the second boom flow rate control valve 157 by the merging control unit 301 is performed at the time of earth removal work or the like. The boom lowering pilot pressure is applied to the lower side (left side) pilot port of the second boom flow rate control valve 157, and the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 is joined to the center bypass oil passage 40L. it can. As a result, the hydraulic excavator according to the first embodiment is located downstream of the second boom flow rate control valve 157 together with the pressure oil discharged from the main pump 12L of the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7. It is supplied to one arm flow control valve 158 and can be reclaimed by the arm 5 during earth removal work or the like. This is because the pressure in the bottom side oil chamber of the boom cylinder 7 becomes higher than the pressure in the rod side oil chamber of the arm cylinder 8 during the earth removal work or the like. Further, the hydraulic excavator according to the first embodiment can change the amount of pressure oil flowing through the merging high-pressure oil passage 157A independently of the lever operation amount in the lowering direction of the boom operation lever 16B. During the earth work or the like, the movement of the arm 5 can be accelerated to a desired speed.

  Further, since the hydraulic excavator according to the first embodiment incorporates the merging high-pressure oil passage 157A in the second boom flow control valve 157, the hydraulic circuit is prevented from being enlarged and complicated, and has a compact and inexpensive structure. While adopting, the above-described effects can be realized.

  Next, a control execution determination process executed by the hydraulic excavator according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the second embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be.

  5 is different from the control execution determination process in FIG. 3 in that the control start condition and the control release condition are different.

  Therefore, the difference will be described in detail while omitting the description of the common points. Further, the same reference numerals as those used for explaining the hydraulic excavator according to the first embodiment are used.

  Schematically, in the control execution determination process of FIG. 5, once it is determined that the control start condition is satisfied, control is performed regardless of the arm opening pilot pressure as long as the boom lowering pilot pressure is equal to or higher than the threshold value β. The determination flag F is maintained at “1”. That is, in the control execution determination process of FIG. 5, once it is determined that the control start condition is satisfied, as long as the lever operation amount in the lowering direction of the boom operation lever 16B is in the intermediate operation region or the upper limit operation region, Regardless of the lever operation amount of the arm operation lever 16A, the control determination flag F is maintained at "1".

  Hereinafter, the control execution determination process of FIG. 5 will be described in detail with reference to a flowchart.

  First, the control execution determination unit 300 determines whether or not the boom lowering pilot pressure is greater than or equal to a threshold value β (step ST21).

  When it is determined that the boom lowering pilot pressure is equal to or higher than the threshold β (YES in step ST21), the control execution determination unit 300 determines whether or not the control determination flag F is “0” (step ST22).

  When it is determined that the control determination flag F is not “0” (“1”) (NO in step ST22), the control execution determination unit 300 maintains the state where the control determination flag F is set to “1”. (Step ST24), the process is returned.

  When it is determined that the control determination flag F is “0” (YES in step ST22), the control execution determination unit 300 determines whether or not the arm opening pilot pressure is greater than or equal to the threshold value α (step ST23).

  When it is determined that the arm opening pilot pressure is greater than or equal to the threshold value α (YES in step ST23), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” to the control determination flag F ( Step ST24).

  When it is determined that the arm opening pilot pressure is less than the threshold value α (NO in step ST23), the control execution determination unit 300 determines that the control start condition is not satisfied and sets “0” in the control determination flag F. (Maintains “0”) (step ST25).

  On the other hand, when it is determined that the boom lowering pilot pressure is less than the threshold β (NO in step ST22), the control execution determination unit 300 determines that the control release condition is satisfied and sets “0” to the control determination flag F. (Step 25).

  With the above configuration, the hydraulic excavator according to the second embodiment, once it is determined that the control start condition is satisfied, as long as the boom lowering pilot pressure is equal to or higher than the threshold β, regardless of the arm opening pilot pressure, The control determination flag F is maintained at “1”. That is, the hydraulic excavator according to the second embodiment frequently determines whether or not to execute the displacement control to the lower side position of the second boom flow rate control valve 157 by the merging control unit 301 due to the fluctuation of the arm opening pilot pressure. Can be prevented from being switched to. As a result, in the hydraulic excavator according to the second embodiment, the pressure oil acting on the pilot port on the lower side (left side) of the second boom flow rate control valve 157 frequently changes and the hydraulic oil flows through the high pressure oil passage 157A for merging. Therefore, it is possible to prevent the movement of the excavation attachment from becoming vibrated.

  Next, a hydraulic excavator according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a schematic diagram illustrating a configuration example of a hydraulic circuit mounted on the hydraulic excavator according to the third embodiment. In FIG. 6, as in FIG. 2, the high pressure oil passage, the pilot oil passage, and the electric drive / control system are indicated by a solid line, a broken line, and a dotted line, respectively. FIG. 7 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the third embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be.

  FIG. 6 differs from the hydraulic circuit according to the first embodiment of FIG. 2 in that it includes an arm rod pressure sensor 17D and an arm bottom pressure sensor 17E, but is common in other points.

  The control execution determination process of FIG. 7 is different from the control execution determination process according to the first embodiment of FIG. 3 in that it includes step ST33 for determining whether or not the arm rod pressure is equal to or higher than the arm bottom pressure. It is common in other points.

  Therefore, the difference will be described in detail while omitting the description of the common points. Further, the same reference numerals as those used for explaining the hydraulic excavator according to the first embodiment are used.

  The arm rod pressure sensor 17 </ b> D is a pressure sensor that detects the pressure in the rod side oil chamber of the arm cylinder 8, and outputs the detected value to the controller 30.

  The arm bottom pressure sensor 17 </ b> E is a pressure sensor that detects the pressure in the bottom side oil chamber of the arm cylinder 8, and outputs the detected value to the controller 30.

  The control execution determination unit 300 determines that the boom lowering pilot pressure is equal to or higher than the threshold value β (YES in step ST31), and determines that the arm opening pilot pressure is equal to or higher than the threshold value α (YES in step ST32). It is determined whether or not the pressure is equal to or higher than the arm bottom pressure (step ST33).

  Specifically, the control execution determination unit 300 determines whether or not the arm rod pressure is equal to or higher than the arm bottom pressure based on the outputs of the arm bottom pressure sensor 17D and the arm rod pressure sensor 17E.

  When it is determined that the arm rod pressure is equal to or higher than the arm bottom pressure (YES in step ST33), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” to the control determination flag F ( Step ST34).

  On the other hand, when it is determined that the arm rod pressure is less than the arm bottom pressure (NO in step ST33), the control execution determination unit 300 determines that the control start condition is not satisfied (the control release condition is satisfied). “0” is set to the control determination flag F (step ST35). This is because when the arm 5 is operated in the opening direction, the arm rod pressure becomes larger than the arm bottom pressure because the pressure oil discharged from the main pumps 12L and 12R flows into the rod side oil chamber of the arm cylinder 8. .

  Thus, the control execution determination unit 300 has the lever operation amount in the lowering direction of the boom operation lever 16B in the intermediate operation region or the upper limit side operation region, and the lever operation amount in the opening direction of the arm operation lever 16A is the upper limit side. It is determined that it is in the operation region, and further, it is determined that the control start condition is satisfied after confirming that the arm rod pressure is equal to or higher than the arm bottom pressure.

  The hydraulic excavator according to the third embodiment includes a boom bottom pressure sensor and a boom rod pressure sensor (both not shown) instead of or in addition to the arm bottom pressure sensor 17D and the arm rod pressure sensor 17E. You may make it prepare. In this case, the control execution determination unit 300 determines that the arm rod pressure is equal to or higher than the arm bottom pressure, and the boom bottom pressure is equal to or higher than the boom rod pressure based on the outputs of the boom bottom pressure sensor and the boom rod pressure sensor. If it is determined, it may be determined that the soil is being discharged. Further, instead of determining that the arm rod pressure is equal to or higher than the arm bottom pressure, the control execution determination unit 300 determines that the control start condition is satisfied when it is determined that the boom bottom pressure is equal to or higher than the boom rod pressure. You may do it. This is because when the boom 4 is operated in the lowering direction, the boom bottom pressure becomes larger than the boom rod pressure because the pressure oil flowing out from the bottom side oil chamber of the boom cylinder 7 is metered out.

  The hydraulic excavator according to the third embodiment includes a bucket bottom pressure sensor and a bucket rod pressure sensor (both not shown) instead of or in addition to the arm bottom pressure sensor 17D and the arm rod pressure sensor 17E. You may make it prepare. In this case, the control execution determination unit 300 determines that the arm rod pressure is equal to or higher than the arm bottom pressure, and the bucket rod pressure is equal to or higher than the bucket bottom pressure based on the output of the bucket bottom pressure sensor and the bucket rod pressure sensor. May be determined that the control start condition is satisfied. Further, instead of determining that the arm rod pressure is equal to or higher than the arm bottom pressure, the control execution determination unit 300 determines that the control start condition is satisfied when it is determined that the bucket rod pressure is equal to or higher than the bucket bottom pressure. You may do it. This is because when the bucket 6 is operated in the opening direction, the bucket rod pressure becomes larger than the bucket bottom pressure because the pressure oil discharged from the main pumps 12L and 12R flows into the rod side oil chamber of the bucket cylinder 9. .

  With the above configuration, whether or not the control execution determination unit 300 executed by the hydraulic excavator according to the third embodiment executes the displacement control of the second boom flow rate control valve 157 to the lower side position by the merging control unit 301 is performed. The determination result can be made more reliable. As a result, the control execution determination unit 300 carelessly sets the arm 5 in spite of the fact that the control start condition is satisfied (the control start condition is not satisfied) due to the erroneous determination that the earthing operation or the like is not performed. It is possible to prevent the movement from being accelerated.

  Next, a hydraulic excavator according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the fourth embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be. The hydraulic excavator according to the fourth embodiment is assumed to be equipped with the hydraulic circuit shown in FIG.

  The control execution determination process of FIG. 8 is different from the control execution determination process according to the second embodiment of FIG. 5 in that it has step ST44 for determining whether or not the arm rod pressure is equal to or higher than the arm bottom pressure. In common.

  Therefore, the difference will be described in detail while omitting the description of the common points. Further, the same reference numerals as those used for explaining the hydraulic excavator according to the first embodiment are used.

  When it is determined that the control determination flag F is “0” (YES in step ST42), the control execution determination unit 300 determines whether or not the arm opening pilot pressure is greater than or equal to α (step ST43).

  When it is determined that the arm opening pilot pressure is greater than or equal to α (YES in step ST43), the control execution determining unit 300 further determines whether or not the arm rod pressure is equal to or higher than the arm bottom pressure (step ST44).

  When it is determined that the arm rod pressure is equal to or higher than the arm bottom pressure (YES in step ST44), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” to the control determination flag F ( Step ST45).

  On the other hand, when it is determined that the arm rod pressure is less than the arm bottom pressure (NO in step ST44), the control execution determination unit 300 determines that the control start condition is not satisfied and sets “0” in the control determination flag F. Is set (step ST46). This is because when the arm 5 is operated in the opening direction, the arm rod pressure becomes larger than the arm bottom pressure because the pressure oil discharged from the main pumps 12L and 12R flows into the rod side oil chamber of the arm cylinder 8. .

  Note that the hydraulic excavator according to the fourth embodiment is similar to the third embodiment in that a bucket bottom is used instead of or in addition to the arm bottom pressure sensor 17D and the arm rod pressure sensor 17E (see FIG. 6). A pressure sensor and a bucket rod pressure sensor (both not shown), or a boom bottom pressure sensor and a boom rod pressure sensor (both not shown) may be provided.

  With the above configuration, the control execution determination unit 300 mounted on the hydraulic excavator according to the fourth embodiment once makes a temporary determination that the control start condition is satisfied, and the boom lowering pilot pressure is equal to or higher than the threshold value β. As long as the arm rod pressure is equal to or higher than the arm bottom pressure, the control determination flag F is maintained at “1” regardless of the arm opening pilot pressure. That is, the control execution determination unit 300 determines whether or not to execute the displacement control of the second boom flow rate control valve 157 to the lower side position by the merging control unit 301 based on fluctuations in the arm opening pilot pressure, the arm rod pressure, and the arm bottom pressure. It is possible to prevent frequent switching of the determination result. As a result, in the hydraulic excavator according to the fourth embodiment, the pressure oil acting on the pilot port on the lower side (left side) of the second boom flow rate control valve 157 frequently changes, and the hydraulic oil flows through the high pressure oil passage 157A for merging. Therefore, it is possible to prevent the movement of the excavation attachment from becoming vibrated.

Further, the control execution determination unit 300 can make the determination result of whether or not to execute the displacement control to the lower side position of the second boom flow rate control valve 157 by the merge control unit 301 more reliable. . As a result, the control execution determination unit 300 may inadvertently speed up the movement of the arm 5 even if the earthing operation or the like is not performed due to an erroneous determination that the control start condition is satisfied, or the control start condition is It is possible to prevent the boom bottom pressure from being reused due to merging even though the earth removal work or the like is being performed due to the erroneous determination that it has been established.

  Next, a hydraulic excavator according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a schematic diagram showing a configuration example of a hydraulic circuit mounted on the hydraulic excavator according to the fifth embodiment. 9, as in FIGS. 2 and 6, the high pressure oil passage, the pilot oil passage, and the electric drive / control system are indicated by a solid line, a broken line, and a dotted line, respectively. FIG. 10 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the fifth embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be.

  9 is different from the hydraulic circuit according to the first embodiment of FIG. 2 in that it includes discharge pressure sensors 17F and 17G, but is common in other points.

  Further, the control execution determination process of FIG. 10 according to the first embodiment of FIG. 3 includes a step ST53 for determining whether or not both discharge pressures of the main pumps 12L and 12R are equal to or higher than a predetermined threshold ζ. Although it differs from the control execution determination process, it is common in other points.

  Therefore, the difference will be described in detail while omitting the description of the common points. Further, the same reference numerals as those used for explaining the hydraulic excavator according to the first embodiment are used.

  The discharge pressure sensor 17F is a pressure sensor that detects the discharge pressure of the main pump 12L, and outputs the detected value to the controller 30.

  The discharge pressure sensor 17G is a pressure sensor that detects the discharge pressure of the main pump 12R, and outputs the detected value to the controller 30.

  The control execution determination unit 300 determines that the boom lowering pilot pressure is equal to or higher than the threshold value β (YES in step ST51), and determines that the arm opening pilot pressure is equal to or higher than the threshold value α (YES in step ST52). It is determined whether or not both of the discharge pressures 12L and 12R are equal to or higher than the threshold value ζ (step ST53).

  Specifically, the control execution determination unit 300 determines whether or not both of the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold ζ based on the outputs of the discharge pressure sensors 17F and 17G.

  When it is determined that both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ (YES in step ST53), the control execution determination unit 300 determines that the control start condition is satisfied and sets the control determination flag F to “ 1 "is set (step ST54).

  On the other hand, when it is determined that at least one of the discharge pressures of the main pumps 12L and 12R is less than the threshold ζ (NO in step ST53), the control execution determination unit 300 does not satisfy the control start condition (the control start condition is The control determination flag F is set to “0” (step ST55). This is because the discharge pressure of the main pumps 12L, 12R becomes equal to or higher than the threshold value ζ in order to allow the pressure oil to flow into the rod side oil chamber of the arm cylinder 8 during the earth removal work or the like.

  Thus, the control execution determination unit 300 has the lever operation amount in the lowering direction of the boom operation lever 16B in the intermediate operation region or the upper limit side operation region, and the lever operation amount in the opening direction of the arm operation lever 16A is the upper limit side. It is determined that it is in the operation region, and further, it is determined that the control start condition is satisfied after confirming that both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ.

  With the above configuration, whether or not the control execution determination unit 300 executed by the hydraulic excavator according to the fifth embodiment executes the displacement control of the second boom flow rate control valve 157 to the lower side position by the merging control unit 301 is performed. The determination result can be made more reliable. As a result, the control execution determination unit 300 inadvertently sets the arm 5 in spite of the fact that the earth start operation is not performed due to an erroneous determination that the control start condition is satisfied (the control release condition is not satisfied). It is possible to prevent the movement from being accelerated, and conversely, the boom bottom pressure is not reclaimed due to the merging even though the earth removal work or the like is being performed.

  Next, a hydraulic excavator according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a flowchart showing the flow of the control execution determination process executed by the hydraulic excavator according to the sixth embodiment. This control execution determination process is continuously executed while the hydraulic excavator is operating. Shall be. The hydraulic excavator according to the sixth embodiment is assumed to be equipped with the hydraulic circuit shown in FIG.

  The control execution determination process of FIG. 11 includes a control execution determination process according to the second embodiment of FIG. 5 in that it includes step ST64 for determining whether or not both discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ. This is different from the above but common in other points.

  Therefore, the difference will be described in detail while omitting the description of the common points. Further, the same reference numerals as those used for explaining the hydraulic excavator according to the first embodiment are used.

  When it is determined that the control determination flag F is “0” (YES in step ST62), the control execution determination unit 300 determines whether or not the arm opening pilot pressure is greater than or equal to α (step ST63).

  When it is determined that the arm opening pilot pressure is greater than or equal to α (YES in step ST63), the control execution determination unit 300 further determines whether or not both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold ζ. (Step ST64).

  When it is determined that both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ (YES in step ST64), the control execution determination unit 300 determines that the control start condition is satisfied and sets the control determination flag F to “ 1 "is set (step ST65).

  On the other hand, when it is determined that both the discharge pressures of the main pumps 12L and 12R are less than the threshold value ζ (NO in step ST64), the control execution determination unit 300 determines that the control start condition is not satisfied and performs control determination. “0” is set to the flag F (“0” is maintained) (step ST66). This is because the discharge pressure of the main pumps 12L, 12R becomes equal to or higher than the threshold value ζ in order to allow the pressure oil to flow into the rod side oil chamber of the arm cylinder 8 during the earth removal work or the like.

  With the above configuration, the control execution determination unit 300 mounted on the hydraulic excavator according to the sixth embodiment has the boom lowering pilot pressure equal to or higher than the threshold β once the provisional determination that the control start condition is satisfied is once made. As long as the arm opening pilot pressure is maintained, the control determination flag F is maintained at “1” regardless of whether or not both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ. That is, the control execution determination unit 300 executes displacement control of the second boom flow rate control valve 157 to the lower side position by the merging control unit 301 by fluctuations in fluctuations in the arm opening pilot pressure and the discharge pressures of the main pumps 12L and 12R. It can be prevented that the determination result of whether or not is frequently switched. As a result, in the hydraulic excavator according to the sixth embodiment, the pressure oil acting on the pilot port on the lower side (left side) of the second boom flow rate control valve 157 changes frequently and flows through the high pressure oil passage 157A for merging. Therefore, it is possible to prevent the movement of the excavation attachment from becoming vibrated.

Further, the control execution determination unit 300 can make the determination result of whether or not to execute the displacement control to the lower side position of the second boom flow rate control valve 157 by the merge control unit 301 more reliable. . As a result, the control execution determination unit 300 speeds up the movement of the arm 5 or the control start condition is satisfied even though the earth removal operation or the like is not performed due to an erroneous determination that the control start condition is satisfied. It is possible to prevent the boom bottom pressure from being reclaimed due to the merging even though the earth removal work or the like is being performed due to the erroneous determination that the control release condition is satisfied.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the proportional solenoid valve 21 electrically changes its output pressure in accordance with the control command current from the controller 30, but its output pressure in accordance with the arm opening pilot pressure and the boom lowering pilot pressure. May be changed hydraulically.

  In the above-described embodiment, the control execution determination unit 300 determines whether the arm rod pressure is equal to or higher than the arm bottom pressure, whether the bucket rod pressure is equal to or higher than the bucket bottom pressure, and the boom bottom pressure is equal to the boom rod pressure. Whether or not both of the discharge pressures of the main pumps 12L and 12R are equal to or higher than a predetermined threshold value ζ is determined by the lowering position of the second boom flow control valve 157 by the merging control unit 301. It is executed individually to confirm whether or not to execute displacement control. However, the control execution determination unit 300 is configured to confirm whether or not to execute the displacement control to the lower side position of the second boom flow rate control valve 157 by the merging control unit 301 by arbitrarily combining these determinations. Also good. Further, the control execution determination unit 300 determines whether the attitude of the excavation attachment is a predetermined attitude based on the outputs of the arm angle sensor, the boom angle sensor, the bucket angle sensor, and the like, and the determination result is used as the merge control unit. The second boom flow control valve 157 may be used for confirming whether or not to execute the displacement control to the lower side position by 301.

DESCRIPTION OF SYMBOLS 1 ... Lower traveling body 2 ... Turning mechanism 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10 ... Cabin 12L, 12R ... Main pump 13L, 13R ... Regulator 16A ... Arm operation lever 16B ... Boom operation lever 16C ... Bucket operation lever 17A ... Arm opening Pilot pressure sensor 17B ... Boom lowering pilot pressure sensor 17C ... Bucket closing pilot pressure sensor 17D ... Arm rod pressure sensor 17E ... Arm bottom pressure sensor 17F, 17G ... Discharge pressure sensor 18 ... Main relief valve 19L, 19R ... Relief valve 20L, 20R ... Negative control throttle 21 ... proportional solenoid valve 30 ... controller 40L, 40R ... center bypass oil passage 41L, 41R ... negative control pressure passage 150 ... control valve (straight traveling valve)
151-160... Flow control valve 300... Control execution determination unit 301.

Claims (5)

A construction machine having an attachment including an arm and a boom,
An arm operation amount detector for detecting an arm operation amount;
A boom operation amount detector for detecting a boom operation amount;
A first boom flow rate control valve that is displaced in the raising-side position direction according to the boom operation amount in the raising direction and is displaced in the lower-side position direction according to the boom operation amount in the lowering direction;
A second boom flow rate control valve that is displaced in the direction of the raising side according to the amount of boom operation in the raising direction;
A control execution determination unit that determines whether or not a predetermined work is being performed by the attachment; and a displacement of the second boom flow rate control valve in the downward side position direction is independent of the amount of boom operation in the downward direction. A control device having a controllable confluence control unit,
The lower side position of the second boom flow rate control valve is such that the pressure oil flowing out from the bottom side oil chamber of the boom cylinder is placed in the center bypass oil passage according to the amount of displacement in the lower side position direction of the second boom flow rate control valve. Has an oil passage to merge,
When the control execution determination unit determines that the boom operation amount in the lowering direction is in a predetermined intermediate operation region and the arm operation amount in the opening direction is in a predetermined upper limit side operation region by the control execution determination unit. The second boom flow rate control valve is displaced to the lowered position by the merge control unit.
Construction machinery characterized by that. The merging control unit changes a displacement amount of the second boom flow rate control valve in a lower side position direction according to a pressure of a bottom side oil chamber of the boom cylinder;
The construction machine according to claim 1. The merging control unit changes the amount of displacement of the second boom flow control valve in the lower side position direction according to the lower boom operation amount.
The construction machine according to claim 1. The merging control unit changes a displacement amount of the second boom flow control valve in a lower side position direction according to a pressure of a bottom side oil chamber of the boom cylinder and a boom operation amount in a lowering direction;
The construction machine according to claim 1. The merging control unit changes the amount of displacement of the second boom flow rate control valve in the lower side position direction stepwise.
The construction machine according to any one of claims 1 to 4 , wherein

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