JP5631799B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine in which a hydraulic circuit having a meter-out throttle is mounted on an oil passage connecting a hydraulic cylinder and an oil tank.

  2. Description of the Related Art Conventionally, there has been known a hydraulic circuit for a construction machine including a meter-out throttle and a safety valve in an oil passage connecting a hydraulic cylinder and an oil tank (for example, see Patent Document 1).

  The hydraulic circuit of Patent Literature 1 includes a meter-out throttle for preventing the pressure oil in the rod-side oil chamber of the arm cylinder from suddenly flowing out toward the oil tank. The meter-out throttle generates a back pressure when the pressure oil in the rod-side oil chamber of the arm cylinder flows out toward the oil tank, so that the piston of the arm cylinder suddenly extends in the rod extension direction against the will of the operator. To move to.

  On the other hand, the hydraulic circuit of Patent Document 1 includes a safety valve that prevents the pressure in the oil passage from rising excessively. The safety valve includes a variable relief valve and a controller that controls the relief pressure of the variable relief valve. The controller reduces the relief pressure in response to an increase in the pressure in the bottom oil chamber of the arm cylinder or an increase in the lever operation amount of the arm operation lever for allowing the pressure oil to flow into the bottom oil chamber of the arm cylinder. That is, the safety valve has a function of allowing the pressure oil in the rod side oil chamber to flow out toward the oil tank without receiving a large back pressure, in addition to the function as a safety valve for preventing excessive pressure from being generated. Have

  In this way, the hydraulic circuit disclosed in Patent Document 1 is configured such that when the operator tries to extend the rod of the arm cylinder (when performing an operation of closing the arm), the rod in the arm cylinder does not go through the meter-out throttle by the safety valve. The pressure oil in the side oil chamber can flow out toward the oil tank. That is, the hydraulic circuit of Patent Document 1 enables the piston of the arm cylinder to move efficiently in the rod extending direction without receiving a large back pressure, and suppresses wasteful energy consumption when closing the arm.

JP 2010-133432 A

  However, since the hydraulic circuit of Patent Document 1 always reduces the relief pressure when the operator tries to extend the rod of the arm cylinder, the arm moves faster when the arm is closed in the air. In some cases, it is impossible to realize the movement of the arm in line with the intention.

  In view of the above-described points, an object of the present invention is to provide a construction machine that avoids wasteful energy consumption caused by a meter-out aperture and that moves the excavation attachment in accordance with the operator's intention. .

In order to achieve the above-described object, a construction machine according to an embodiment of the present invention is a construction machine having a drilling attachment including an arm and a boom, and is disposed in an oil passage connecting an arm cylinder and a meter-out throttle. A variable relief valve, an arm operation amount detection unit that detects an arm operation amount, a boom operation amount detection unit that detects a boom operation amount, and whether or not the arm operation amount and the boom operation amount satisfy a predetermined condition And a control device having a relief pressure control unit for controlling the relief pressure of the variable relief valve. The control device has a predetermined arm operation amount in the closing direction by the control execution judgment unit. In the upper limit side operation area, and when it is determined that the boom operation amount in the raising direction is in the predetermined intermediate operation area, the relief pressure control unit controls the variable release And changes to be lower setting of the relief pressure of the valve.

  By the above-described means, the present invention can provide a construction machine that avoids wasteful energy consumption due to the meter-out aperture and makes the movement of the excavation attachment follow the operator's will.

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 relief pressure change process performed with the hydraulic shovel which concerns on a 1st Example. It is an opening diagram of the closed side position in the 1st arm flow control valve. It is a figure which shows an example of transition of the total opening area of the oil path which connects the rod side oil chamber of an arm cylinder, and an oil tank. 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 to the oil tank through the center bypass pipes 40L and 40R.

  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 159 via high-pressure oil passages, and are, for example, swash plate type variable displacement hydraulic pumps. The pump control method of the main pumps 12L and 12R may be any of negative control control, positive control control, load sensing control, and the like.

  The center bypass conduit 40L is a high-pressure oil passage that communicates the flow control valves 151, 153, 155, 157, and 158. The center bypass conduit 40R includes the control valve 150 and the flow control valves 152, 154, 156, and 159 is a high-pressure oil passage communicating with 159.

  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 the flow rate control valve 151 and the flow rate control valve 152 in order to improve the straightness of the lower traveling body 2. be able to.

  The flow 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 traveling hydraulic motor (not shown). This is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged from the pump 12L or 12R by a right traveling hydraulic motor (not shown).

  The flow control valve 153 is a spool valve that switches the flow of pressure oil so that the pressure oil discharged from the main pump 12L or 12R is circulated by 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 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 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 first arm flow control valve 158 includes a meter-out restrictor 158A at the CT port that connects the rod-side oil chamber of the arm cylinder 8 and the oil tank at the closed position (the spool position on the right side in the figure).

  The meter-out restrictor 158A is a restrictor for preventing the pressure oil in the rod side oil chamber in the arm cylinder 8 from suddenly flowing toward the oil tank when the arm operation lever 16A is operated in the closing direction. .

  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. It is introduced into either the left or right pilot port of the control valve 158. In the first embodiment, the arm operation lever 16A introduces pressure oil into the pilot port on the right side of the second arm flow control valve 159 when the lever operation amount in the closing direction is equal to or greater than the predetermined lever operation amount. I will let you.

  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 on either the left or right side of the first boom flow control valve 156. It is introduced in the pilot port. In the first embodiment, the boom operation lever 16B introduces pressure oil into the pilot port on the right side of the second boom flow control valve 157 when the lever operation amount in the raising direction is equal to or greater than the predetermined lever operation amount. I will let you.

  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 closing 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 closing direction of the arm operation lever 16A as a pressure, and the detected value is a controller. 30 is output.

  The boom raising 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 raising direction of the boom operation lever 16B as a pressure, and the detected value is a controller. 30 is output.

  The bucket closing 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 closing 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 19 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 variable relief valve 20 controls the pressure of the rod-side oil chamber to be less than the predetermined relief pressure by discharging the pressure oil to the oil tank when the pressure of the rod-side oil chamber in the arm cylinder 8 exceeds a predetermined relief pressure. It is a safety valve.

  The variable relief valve 20 can change its relief pressure in accordance with a control signal output from the controller 30, and preferably reduces the relief pressure in accordance with the control signal.

  Note that the variable relief valve 20 may be attached in the form of replacing an existing safety valve whose relief pressure is fixed, or may be attached independently of the existing safety valve. When replacing an existing safety valve, there is an effect of reducing the cost required for mounting the variable relief valve 20.

  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 out programs corresponding to the control execution determination unit 300 and the relief pressure control unit 301 from a nonvolatile storage medium such as a ROM and develops the programs on a volatile storage medium such as a RAM, respectively. Causes the CPU to execute processing.

  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 relief pressure control unit 301 based on the detection values.

  Thereafter, the controller 30 appropriately outputs control signals corresponding to the processing results of the control execution determination unit 300 and the relief pressure control unit 301 to the variable relief valve 20.

  The control execution determination unit 300 is a functional element for determining whether or not a relief pressure changing process (described later) by the relief pressure control unit 301 is executed during excavation / flooring work by excavation attachment, for example, arm operation Based on the lever operation amount in the closing direction of the lever 16A and the lever operation amount in the raising direction of the boom operation lever 16B, it is determined whether or not a control start condition (control release condition) is satisfied.

  Specifically, in the control execution determination unit 300, the lever operation amount in the closing direction of the arm operation lever 16A is in a predetermined upper limit side operation region, and the lever operation amount in the raising direction of the boom operation lever 16B is in the predetermined intermediate range. When it is in the operation area, it is determined that the control start condition is satisfied.

  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 closing 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 upward direction.

  More specifically, the intermediate operation area is a direction in which the boom 4 is raised to prevent the hydraulic excavator from being jacked up during excavation / flooring (while the arm 5 is operated in the closing direction). This includes the lever operation amount of the boom operation lever 16B when the boom operation lever 16B is operated to operate the boom operation lever 16B.

  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 relief pressure control unit 301 is a functional element for controlling the relief pressure of the variable relief valve 20, and hereinafter, the process in which the relief pressure control unit 301 changes the relief pressure is referred to as “relief pressure changing process”.

  For example, when the control execution determination unit 300 determines that the control start condition is satisfied, the relief pressure control unit 301 decreases the relief pressure of the variable relief valve 20. In this case, the relief pressure after the decrease may be a constant value registered in advance, or may be a variable value that changes according to the pressure in the rod side oil chamber of the arm cylinder 8. Further, the reduction of the relief pressure may be switched stepwise toward a constant value or a variable value, or may be switched so as to gradually decrease toward a constant value or a variable value at a constant time.

  Further, the relief pressure control unit 301 determines that the control start condition is satisfied by the control execution determination unit 300 and lowers the relief pressure, and then the control execution determination unit 300 does not satisfy the control start condition (control If it is determined again that the release condition is satisfied, the relief pressure of the variable relief valve 20 is returned to the original value.

  The relief pressure control unit 301 sets the relief pressure at the time of non-control low, and the control execution determination unit 300 determines that the control start condition is not satisfied (the control release condition is satisfied). In addition, the relief pressure of the variable relief valve 20 may be increased. As a result, the relief pressure during excavation / flooring can be made lower than the relief pressure when not excavating / flooring.

  Here, with reference to FIG. 3, the control execution determination unit 300 determines whether to execute the relief pressure changing process by the relief pressure control unit 301 during the excavation / flooring operation by the excavation attachment (hereinafter, referred to as “removal pressure change process”). An example of “control execution determination process” 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, the control execution determination unit 300 determines whether the lever operation amount in the closing direction of the arm operation lever 16A is in the upper limit side operation region, and whether the lever operation amount in the upward direction of the boom operation lever 16B is in the intermediate operation region. Determine whether.

  Specifically, the control execution determination unit 300 determines whether or not the arm closing pilot pressure, which is the output of the arm closing pilot pressure sensor 17A, is equal to or greater than a predetermined threshold value α (step ST1). In this case, the arm closing pilot pressure being equal to or greater than the predetermined threshold value α means that the lever operating amount in the closing direction of the arm operating lever 16A is in the predetermined upper limit operating region.

  When it is determined that the arm closing pilot pressure is greater than or equal to the threshold value α (YES in step ST1), the control execution determining unit 300 determines that the boom raising pilot pressure, which is the output of the boom raising pilot pressure sensor 17B, is greater than or equal to the predetermined threshold value β. It is determined whether or not it is equal to or less than a predetermined threshold γ (> β) (step ST2). In this case, when the boom raising pilot pressure is not less than the predetermined threshold β and not more than the predetermined threshold γ, it means that the lever operation amount in the raising direction of the boom operation lever 16B is in the predetermined intermediate operation region.

  When it is determined that the boom raising pilot pressure is greater than or equal to the threshold β and less than or equal to the threshold γ (YES in step ST2), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” in the control determination flag F. Is set (step ST3).

  On the other hand, when it is determined that the arm closing pilot pressure is less than the threshold value α (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 closing direction of the arm operation lever 16A is not in the upper limit side operation region.

  Even when it is determined that the arm closing pilot pressure is equal to or higher than the threshold value α, when it is determined that the boom raising pilot pressure is lower than the threshold value β or higher than the threshold value γ (NO in step ST2), the control execution determination is performed. Unit 300 determines that the control start condition is not satisfied (control release condition is satisfied), and sets control determination flag F to “0” (step ST4). This is because it can be determined that the lever operation amount in the raising direction of the boom operation lever 16B is not in the intermediate operation region.

  The control execution determination unit 300 determines whether or not the arm closing pilot pressure is equal to or higher than the threshold value α after determining whether or not the boom raising pilot pressure is equal to or higher than the threshold value β and equal to or lower than the threshold value γ. May be performed, or the determinations may be performed simultaneously. The same applies to other embodiments described below.

  Here, an example of the relief pressure changing process by the relief pressure control unit 301 during the excavation / flooring work by the excavation attachment will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the relief pressure changing process. This relief pressure changing process is continuously executed while the hydraulic excavator is operating.

  First, the relief pressure 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). Step ST12).

  When it is determined that the control determination flag F is “1” (YES in step ST12), the relief pressure control unit 301 outputs a control signal to the variable relief valve 20 to reduce the relief pressure of the variable relief valve 20. (Step ST13).

  Specifically, the relief pressure control unit 301 performs the excavation / flooring operation from the predetermined first set value suitable for the case where the excavation / flooring operation is not performed. To a predetermined second set value suitable for If the relief pressure has already reached the second set value, the relief pressure control unit 301 maintains the relief pressure at the second set value.

  On the other hand, when it is determined that the control determination flag F is not “1” (“0”) (NO in step ST12), the relief pressure control unit 301 outputs a control signal to the variable relief valve 20, and is variable. The relief pressure of the relief valve 20 is returned from the second set value to the first set value (step ST14). If the relief pressure has already reached the first set value, the relief pressure control unit 301 maintains the relief pressure at the first set value.

  In this way, the relief pressure control unit 301 switches the relief pressure of the variable relief valve 20 so that the relief pressure during excavation / flooring is lower than the relief pressure when not excavating / flooring. can do.

  Next, an example of the opening characteristic of the closing position (the spool position on the right side in FIG. 2) in the first arm flow control valve 158 will be described with reference to FIG. FIG. 5 is an opening diagram of the closed position of the first arm flow control valve 158, and the transition of the PT port opening area, the PC port opening area, and the CT port opening area is indicated by a solid line, a broken line, and a one-dot chain line, respectively. . In addition, FIG. 5 additionally shows the transition of the pressure (pilot pressure) acting on the pilot port on the closing side (right side) of the first arm flow control valve 158 by a dotted line. Each line segment representing the opening area belongs to the left vertical axis, and the pilot pressure belongs to the right vertical axis.

  FIG. 5 shows a relationship in which the spool stroke in the closing direction of the first arm flow control valve 158 increases as the pilot pressure increases.

  Further, FIG. 5 shows a transition in which the PT port opening area rapidly decreases until the spool stroke reaches the value P1, and thereafter continues to decrease relatively slowly to reach zero. This transition represents that when the arm operation lever 16A is operated in the closing direction, the pressure oil flowing through the center bypass pipe line 40L decreases according to the lever operation amount.

  Further, FIG. 5 shows a transition in which the PC port opening area starts increasing when the spool stroke is close to the value P2, increases relatively slowly until the spool stroke reaches the value P3, and then increases rapidly. . This transition indicates that when the arm operation lever 16A is operated in the closing direction, an amount of pressure oil corresponding to the lever operation amount can flow into the bottom side oil chamber of the arm cylinder 8.

  FIG. 5 shows a transition in which the CT port opening area starts to increase when the spool stroke is close to the value P2, and increases relatively slowly until the spool stroke reaches the maximum. Even if the arm operation lever 16A is operated in the closing direction, this transition is because the CT port opening area is set to be small, so that the pressure oil oil tank in the rod side oil chamber of the arm cylinder 8 is moved to. This means that sudden outflow of water is prevented.

  Next, an example of transition of the total opening area of the oil passage connecting the rod side oil chamber of the arm cylinder 8 and the oil tank will be described with reference to FIG. In the first embodiment, the oil passage connecting the rod side oil chamber of the arm cylinder 8 and the oil tank is composed of two oil passages, a CT port and an oil passage in which the variable relief valve 20 is disposed, The opening area is represented by the sum of the CT port opening area and the variable relief valve opening area.

  6 (A) to 6 (D) show the arm closing pilot pressure, the CT port opening area, the variable relief valve opening area, and the total opening area (the oil connecting the rod side oil chamber of the arm cylinder 8 and the oil tank). The time course of each (total opening area of the road) is shown.

When the arm operating lever 16A is operated in the closing direction at time t1, the arm closing pilot pressure increases according to the lever operating amount in the closing direction as shown in FIG. 5, and at time t2, the arm operating lever 16A When the lever operation amount in the closing direction reaches the maximum value, the threshold value α is exceeded and the maximum pressure P _MAX is reached.

The CT port opening area increases as the arm closing pilot pressure increases at time t1, and reaches the maximum area A1 _MAX at time t2. The variable relief valve opening area remains zero even at time t2 because the pressure in the rod side oil chamber of the arm cylinder 8 is less than the relief pressure. As a result, the total opening area follows the same transition as the CT port opening area, and reaches the maximum area A1 _MAX of the CT port opening area at time t2.

Thereafter, when the arm closing pilot pressure is equal to or higher than the threshold value α and the boom raising pilot pressure is equal to or higher than the threshold value β and equal to or lower than the threshold value γ at time t3, the control execution determination unit 300 sets “1” to the control determination flag F Then, the relief pressure is switched by the relief pressure control unit 301. When the pressure in the rod side oil chamber of the arm cylinder 8 is greater than the relief pressure after switching, the variable relief valve 20 is fully opened, and the variable relief valve opening area reaches the maximum area A2 _MAX . As a result, the total opening area reaches A1 _MAX + A2 _MAX which is the sum of the CT port opening area and the variable relief valve opening area. The maximum area _{A2 MAX} is preferably than maximum area _{A1 MAX} is a large value, for example, are more than twice the value of the maximum area _{A1 MAX.}

Thus, the variable relief valve opening area increases instantaneously to the maximum area A2 _MAX after the arm closing pilot pressure exceeds the threshold value α, that is, after the CT port opening area reaches the maximum area A1 _MAX. However, the CT port opening area may increase before reaching the maximum area A1 _MAX .

  Further, the variable relief valve 20 instantaneously decreases the relief pressure from the first set value to the second set value when the control start condition is satisfied, but gradually increases the relief pressure from the first set value to the second set value. You may make it reduce to.

  6 (C) and 6 (D) show the variable relief valve opening area when the relief pressure is gradually decreased from the first set value to the second set value when the control start condition is satisfied. Each transition of the total opening area is shown.

As shown by the alternate long and short dash line in FIG. 6C and FIG. 6D, when the relief pressure is gradually reduced, the variable relief valve opening area gradually increases toward the maximum area A2 _MAX. . This is because the variable relief valve opening area tends to increase as the difference between the relief pressure and the pressure in the rod side oil chamber of the arm cylinder 8 (> relief pressure) increases.

  With the above configuration, the hydraulic excavator according to the first embodiment is configured to release the relief of the variable relief valve 20 only when it is determined that the relief pressure control unit 301 needs to switch the relief pressure for excavation / flooring work. By changing the pressure setting, the pressure oil in the rod-side oil chamber in the arm cylinder 8 can flow out toward the oil tank without passing through the meter-out restrictor 158A. As a result, wasteful energy consumption due to the meter-out throttle 158A occurs during excavation / flooring work, or when the arm 5 is closed in the air, such as during horizontal pulling work or the first half of flooring work. It is possible to prevent the movement from becoming faster.

  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. 7 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. The hydraulic excavator according to the second embodiment executes the relief pressure changing process shown in FIG.

  7 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. 7, when it is determined that the control start condition is satisfied, the control determination is performed regardless of the boom raising pilot pressure as long as the arm closing pilot pressure is equal to or higher than the threshold value α. The flag F is maintained at “1”. That is, the control execution determination process of FIG. 7 sets the control determination flag F regardless of the lever operation amount of the boom operation lever 16B as long as the lever operation amount in the closing direction of the arm operation lever 16A is within the predetermined upper limit operation region. Keep “1”.

  Hereinafter, the control execution determination process of FIG. 7 will be described in detail with reference to a flowchart.

  First, the control execution determination unit 300 determines whether or not the arm closing pilot pressure is greater than or equal to the threshold value α (step ST21).

  When it is determined that the arm closing pilot pressure is equal to or higher than the threshold value α (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 boom raising pilot pressure is not less than the threshold value β and not more than the threshold value γ ( Step ST23).

  When it is determined that the boom raising pilot pressure is greater than or equal to the threshold value β and less than or equal to the threshold value γ (YES in step ST23), the control execution determination unit 300 determines that the control start condition is satisfied and sets “1” in the control determination flag F. "Is set (step ST24).

  When it is determined that the boom raising pilot pressure is less than the threshold β or greater than the threshold γ (NO in step ST23), the control execution determination unit 300 determines that the control start condition is not satisfied and sets the control determination flag F. “0” is set (“0” is maintained) (step ST25).

  On the other hand, when it is determined that the arm closing pilot pressure is less than the threshold value α (NO in step ST21), the control execution determination unit 300 determines that the control release condition is satisfied (the control start condition is not satisfied). “0” is set to the control determination flag F (step ST25).

  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 arm closing pilot pressure is equal to or higher than the threshold value α, regardless of the boom raising pilot pressure, The control determination flag F is maintained at “1”. That is, the hydraulic excavator according to the second embodiment can prevent the relief pressure of the variable relief valve 20 from frequently switching due to the fluctuation of the boom raising pilot pressure. As a result, the hydraulic excavator according to the second embodiment can prevent the relief pressure of the variable relief valve 20 from being frequently changed and the movement of the excavation attachment from being vibrated.

  Next, a hydraulic excavator according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a schematic diagram showing a configuration example of a hydraulic circuit mounted on the hydraulic excavator according to the third embodiment. In FIG. 8, 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. 9 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. The hydraulic excavator according to the third embodiment executes the relief pressure changing process shown in FIG.

  FIG. 8 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. 9 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 bottom pressure is equal to or higher than the arm rod 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.

  Control execution determination unit 300 determines that the arm closing pilot pressure is greater than or equal to threshold α (YES in step ST31), and determines that the boom raising pilot pressure is greater than or equal to threshold β and less than or equal to threshold γ (in step ST32). YES), it is determined whether or not the arm bottom pressure is equal to or higher than the arm rod pressure (step ST33).

  Specifically, the control execution determination unit 300 determines whether or not the arm bottom pressure is equal to or higher than the arm rod 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 bottom pressure is equal to or higher than the arm rod 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 bottom pressure is less than the arm rod 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, during excavation and floor excavation work, the arm bottom pressure becomes equal to or higher than the arm rod pressure due to the excavation reaction force received from the ground or the like.

  As described above, the control execution determination unit 300 indicates that the lever operation amount in the closing direction of the arm operation lever 16A is in the upper limit side operation region and the lever operation amount in the upward direction of the boom operation lever 16B is in the intermediate operation region. In addition, after confirming that the arm bottom pressure is equal to or higher than the arm rod pressure, it is determined that the control start condition is satisfied.

  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 bottom pressure is equal to or higher than the arm rod pressure, and the bucket bottom pressure is equal to or higher than the bucket rod 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 bottom pressure is equal to or higher than the arm rod pressure, the control execution determination unit 300 determines that the control start condition is satisfied when it is determined that the bucket bottom pressure is equal to or higher than the bucket rod pressure. You may do it. This is because the bucket bottom pressure becomes equal to or higher than the bucket rod pressure due to the excavation reaction force received from the ground or the like during excavation / floor excavation work.

  With the above configuration, the control execution determination unit 300 that is executed by the hydraulic excavator according to the third embodiment is more reliable in determining whether the relief pressure control unit 301 needs to switch the relief pressure. Can be. As a result, the control execution determination unit 300 causes the arm 5 to move faster or close when the arm 5 is closed in the air due to an erroneous determination that the control start condition is satisfied (the control release condition is not satisfied). It is possible to prevent wasteful energy consumption due to the meter-out aperture 158A from being erroneously determined that the condition is not satisfied (the control release condition is satisfied).

  Next, a hydraulic excavator according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 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 executes the relief pressure changing process shown in FIG. 4 and is equipped with the hydraulic circuit shown in FIG.

  The control execution determination process of FIG. 10 is different from the control execution determination process according to the second embodiment of FIG. 7 in that it includes step ST44 for determining whether or not the arm bottom pressure is equal to or higher than the arm rod 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 boom raising pilot pressure is equal to or higher than the threshold β and equal to or lower than the threshold γ ( Step ST43).

  When it is determined that the boom raising pilot pressure is greater than or equal to the threshold β and less than or equal to the threshold γ (YES in step ST43), the control execution determination unit 300 further determines whether or not the arm bottom pressure is greater than or equal to the arm rod pressure. (Step ST44).

  When it is determined that the arm bottom pressure is equal to or higher than the arm rod 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 bottom pressure is less than the arm rod 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 ("0" is maintained) (step ST46). This is because, during excavation and floor excavation work, the arm bottom pressure becomes equal to or higher than the arm rod pressure due to the excavation reaction force received from the ground or the like.

  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. 8). A pressure sensor and a bucket 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 determines that the control start condition is satisfied, as long as the arm closing pilot pressure is equal to or higher than the threshold value α. Regardless of the boom raising pilot pressure, and regardless of whether the arm bottom pressure is equal to or higher than the arm rod pressure, the control determination flag F is maintained at “1”. That is, the control execution determination unit 300 can prevent the relief pressure from frequently switching due to fluctuations in the boom raising pilot pressure, the arm bottom pressure, or the arm rod pressure. As a result, the hydraulic excavator according to the fourth embodiment can prevent the relief pressure of the variable relief valve 20 from frequently switching and the movement of the excavation attachment from becoming oscillating.

  Further, the control execution determination unit 300 can make the determination result of whether or not the relief pressure control unit 301 needs to switch the relief pressure to be more reliable. As a result, the control execution determination unit 300 causes the meter 5 to move faster when closing the arm 5 in the air due to an erroneous determination that the control start condition is satisfied, or to determine whether the control release condition is satisfied. It is possible to prevent wasteful energy consumption due to the out diaphragm 158A.

  Next, a hydraulic excavator according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a schematic diagram showing a configuration example of a hydraulic circuit mounted on the hydraulic excavator according to the fifth embodiment. In FIG. 11, as in FIGS. 2 and 8, 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. 12 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. The hydraulic excavator according to the fifth embodiment executes the relief pressure changing process shown in FIG.

  FIG. 11 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. 12 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 value 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.

  Control execution determination unit 300 determines that the arm closing pilot pressure is equal to or higher than threshold value α (YES in step ST51), and determines that the boom raising pilot pressure is equal to or higher than threshold value β and equal to or lower than threshold value γ (in step ST52). YES), it is determined whether or not both the discharge pressures of the main pumps 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 value ζ (NO in step ST53), the control execution determination unit 300 does not satisfy the control start condition (the control release condition is The control determination flag F is set to “0” (step ST55). This is because, during excavation and floor excavation work, the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold ζ due to the excavation reaction force received from the ground or the like.

  As described above, the control execution determination unit 300 indicates that the lever operation amount in the closing direction of the arm operation lever 16A is in the upper limit side operation region and the lever operation amount in the upward direction of the boom operation lever 16B is in the intermediate operation region. Further, after confirming that both of the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ, it is determined that the control start condition is satisfied.

  With the above configuration, the control execution determination unit 300 that is executed by the hydraulic excavator according to the fifth embodiment is more reliable in determining whether the relief pressure control unit 301 needs to switch the relief pressure. Can be. As a result, the control execution determination unit 300 causes the arm 5 to move faster or close when the arm 5 is closed in the air due to an erroneous determination that the control start condition is satisfied (the control release condition is not satisfied). It is possible to prevent wasteful energy consumption due to the meter-out aperture 158A from being erroneously determined that the condition is not satisfied (the control release condition is satisfied).

  Next, a hydraulic excavator according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 13 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 executes the relief pressure changing process shown in FIG. 4 and is equipped with the hydraulic circuit shown in FIG.

  The control execution determination process of FIG. 13 includes the step ST64 of determining whether both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ, and the control execution determination process according to the second embodiment of FIG. 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 boom raising pilot pressure is greater than or equal to the threshold β and less than or equal to the threshold γ ( Step ST63).

  When it is determined that the boom raising pilot pressure is greater than or equal to the threshold β and less than or equal to the threshold γ (YES in step ST63), the control execution determination unit 300 further determines that both the discharge pressures of the main pumps 12L and 12R are greater than or equal to the threshold ζ. It is determined whether or not there is (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 in the flag F (step ST66). This is because, during excavation and floor excavation work, the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold ζ due to the excavation reaction force received from the ground or the like.

  With the above configuration, the control execution determination unit 300 mounted on the hydraulic excavator according to the sixth embodiment once determines that the control start condition is satisfied, as long as the arm closing pilot pressure is equal to or higher than the threshold value α. Regardless of the boom raising pilot pressure, and regardless of whether both the discharge pressures of the main pumps 12L and 12R are equal to or higher than the threshold value ζ, the control determination flag F is maintained at “1”. That is, the control execution determination unit 300 can prevent the relief pressure from frequently switching due to fluctuations in the boom raising pilot pressure or the discharge pressures of the main pumps 12L and 12R. As a result, the hydraulic excavator according to the sixth embodiment can prevent the relief pressure of the variable relief valve 20 from frequently switching and the movement of the excavation attachment from vibrating.

  Further, the control execution determination unit 300 can make the determination result of whether or not the relief pressure control unit 301 needs to switch the relief pressure to be more reliable. As a result, the control execution determination unit 300 causes the meter 5 to move faster when closing the arm 5 in the air due to an erroneous determination that the control start condition is satisfied, or to determine whether the control release condition is satisfied. It is possible to prevent wasteful energy consumption due to the out diaphragm 158A.

  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 control execution determination unit 300 determines whether the arm bottom pressure is equal to or higher than the arm rod pressure, whether the bucket bottom pressure is equal to or higher than the bucket rod pressure, or the main pumps 12L and 12R. The determination whether or not both of the discharge pressures are equal to or higher than a predetermined threshold value ζ is executed individually for checking whether or not the relief pressure control unit 301 needs to switch the relief pressure. However, the control execution determination unit 300 may check whether it is necessary to switch the relief pressure by the relief pressure control unit 301 by arbitrarily combining these determinations. Furthermore, the control execution determination unit 300 determines whether the attitude of the excavation attachment is a predetermined attitude based on outputs from the arm angle sensor, the boom angle sensor, the bucket angle sensor, and the like, and the determination result is relief pressure controlled. You may make it use for the confirmation of whether the relief pressure switching by the part 301 is required.

  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 16A ... Arm operation lever 16B ... Boom operation lever 16C ... Bucket operation lever 17A ... Arm closing pilot pressure sensor 17B ... Boom raising pilot pressure sensor 17C ... Bucket closing pilot pressure sensor 17D ... Arm rod pressure sensor 17E ... Arm bottom pressure sensor 17F, 17G ... Discharge pressure sensor 19 ... Main relief valve 20 ... Variable relief valve 30 ... Controller 40L, 40R ... Center bypass conduit 15 ... control valve 151-159 ... flow control valve 300 ... control execution determination unit 301 ... relief pressure controller

Claims (4)

A construction machine with a drilling attachment including an arm and a boom,
A variable relief valve arranged in an oil passage connecting the arm cylinder and the meter-out throttle,
An arm operation amount detector for detecting an arm operation amount;
A boom operation amount detector for detecting a boom operation amount;
A control execution unit that determines whether or not the arm operation amount and the boom operation amount satisfy a predetermined condition, and a control device that includes a relief pressure control unit that controls a relief pressure of the variable relief valve,
When the control execution determination unit determines that the arm operation amount in the closing direction is in the predetermined upper limit side operation region and the boom operation amount in the raising direction is in the predetermined intermediate operation region, the control device The relief pressure control unit changes the relief pressure setting of the variable relief valve to be low .
Construction machinery characterized by that. A cylinder pressure detection unit for detecting the pressure of each of the rod side oil chamber and the bottom side oil chamber of the arm cylinder;
Wherein the control execution determining section, that the pressure of the bottom-side oil chamber is equal to or greater than the pressure of the rod side oil chamber, the additional conditions for changing to be lower setting of the relief pressure of the variable relief valve ,
The construction machine according to claim 1. A discharge pressure detector for detecting a discharge pressure of a hydraulic pump that supplies pressure oil to the arm cylinder;
The control execution determination unit sets the increase in the discharge pressure as an additional condition for changing the setting of the relief pressure of the variable relief valve to be low .
The construction machine according to claim 1 or 2, characterized in that. A posture detecting unit for detecting the posture of the excavation attachment;
The control execution determination unit sets the excavation attachment in a predetermined posture as an additional condition for changing the setting of the relief pressure of the variable relief valve to be low .
The construction machine according to any one of claims 1 to 3, wherein

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