JP6490458B2 - Excavator - Google Patents

Description

  The present invention relates to an excavator.

  2. Description of the Related Art Conventionally, there is known an excavator that adjusts turning torque using a two-stage relief valve as a turning relief valve of a turning hydraulic motor (for example, see Patent Document 1).

  This excavator sets the swing relief pressure to the step-down side when the motor capacity of the swing hydraulic motor is increased, or sets the swing relief pressure to the step-up side when the motor capacity of the swing hydraulic motor is decreased. The rotating hydraulic motor is rotated while draining hydraulic oil from the two-stage relief valve. Then, the turning torque is made the same in both the case of performing the low speed turning and the case of performing the high speed turning.

JP-A-6-17447

  However, the above-described excavator does not control the swing hydraulic motor with hydraulic oil having a pressure lower than the swing relief pressure of the two-stage relief valve. Therefore, the size of the turning torque that can be used is limited to a narrow range.

  In view of the above, it is desirable to provide an excavator that can expand the range of available swing torque magnitudes.

  An excavator according to an embodiment of the present invention includes a turning hydraulic motor, a variable displacement hydraulic pump that supplies hydraulic oil to the turning hydraulic motor, and a pipe line that connects the turning hydraulic motor and the hydraulic pump. And a controller for controlling the turning torque of the turning hydraulic motor, wherein the controller increases or decreases the displacement volume of the hydraulic pump to increase the turning hydraulic circuit internal pressure of the turning relief valve. The turning torque of the turning hydraulic motor is controlled by adjusting to a predetermined pressure lower than the cracking pressure.

  By the above-described means, it is possible to provide an excavator that can expand the range of the magnitude of the turning torque that can be used.

It is a figure which shows the structural example of the shovel which concerns on the Example of this invention. It is a circuit diagram which shows the structural example of the hydraulic system mounted in the shovel of FIG. It is a negative control chart showing the relationship between the pump flow rate and the negative control pressure. It is a horsepower control diagram (PQ diagram) showing the relationship between pump flow rate and pump discharge pressure. It is the schematic which shows the structural example of a turning hydraulic circuit. It is a figure which shows the relationship between a turning hydraulic circuit internal pressure and a turning relief flow volume. It is a figure which shows the structural example of a control system. It is a figure which shows the time transition of a turning lever operation amount and a turning hydraulic circuit internal pressure.

  Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of an excavator as a construction machine according to an embodiment of the present invention. The excavator in FIG. 1 includes a turning mechanism 2 on a crawler type lower traveling body 1. Moreover, the turning mechanism 2 mounts the upper turning body 3 so as to be turnable around the X axis.

  Further, the upper swing body 3 includes a drilling attachment which is an example of an attachment at the front center portion. The excavation attachment includes a boom 4, an arm 5, and a bucket 6, and includes a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 as hydraulic actuators.

  The posture detection device M1 includes a boom angle sensor, an arm angle sensor, a bucket angle sensor, and a vehicle body tilt sensor. The boom angle sensor is a sensor that acquires the boom angle. For example, the rotation angle sensor that detects the rotation angle of the boom foot pin, the stroke sensor that detects the stroke amount of the boom cylinder 7, and the inclination that detects the inclination angle of the boom 4. Includes (acceleration) sensors. The arm angle sensor is a sensor that acquires the arm angle. For example, the rotation angle sensor that detects the rotation angle of the arm connecting pin, the stroke sensor that detects the stroke amount of the arm cylinder 8, and the inclination that detects the inclination angle of the arm 5. Includes (acceleration) sensors. The bucket angle sensor is a sensor that acquires the bucket angle. For example, the rotation angle sensor that detects the rotation angle of the bucket connecting pin, the stroke sensor that detects the stroke amount of the bucket cylinder 9, and the inclination that detects the inclination angle of the bucket 6. Includes (acceleration) sensors. The vehicle body tilt sensor is a sensor that acquires the airframe tilt angle, and includes, for example, a biaxial tilt (acceleration) sensor.

  FIG. 2 is a circuit diagram showing a configuration example of the hydraulic system 100 mounted on the excavator of FIG. The hydraulic system 100 includes hydraulic pumps 14L and 14R driven by a drive source (not shown) such as an engine or an electric motor. Hereinafter, the hydraulic pumps 14L and 14R may be collectively referred to as “hydraulic pump 14”. The same applies to the other components configured by a pair of left and right. The hydraulic pump 14 is a variable displacement hydraulic pump that makes the displacement volume (cc / rev) per rotation variable. The hydraulic pump 14L circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass pipe line 50L that communicates the control valves 171, 173, 175, and 177. Similarly, the hydraulic pump 14R circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass pipe line 50R that communicates the control valves 170, 172, 174, 176, and 178.

  The control valve 170 is a spool valve as a traveling straight valve. In the present embodiment, the control valve 170 operates both the traveling hydraulic motors 42L and 42R with the hydraulic oil discharged from the hydraulic pump 14L and the traveling hydraulic motor 42L with the hydraulic oil discharged from the hydraulic pump 14L. And the mode in which the traveling hydraulic motor 42R is operated by the hydraulic oil discharged from the hydraulic pump 14R is switched.

  The control valve 171 is a spool valve that switches the flow of hydraulic oil in order to supply the hydraulic oil discharged from the hydraulic pump 14L to the traveling hydraulic motor 42L as a hydraulic actuator.

  The control valve 172 is a spool valve that switches the flow of hydraulic oil in order to supply the hydraulic oil discharged from the hydraulic pump 14R to the traveling hydraulic motor 42R.

  The control valve 173 is a spool valve that switches the flow of hydraulic oil in order to supply the hydraulic oil discharged from the hydraulic pump 14L to the turning hydraulic motor 21 as a hydraulic actuator.

  The control valve 174 is a spool valve for supplying hydraulic oil discharged from the hydraulic pump 14R to the bucket cylinder 9 as a hydraulic actuator and discharging the hydraulic oil in the bucket cylinder 9 to the hydraulic oil tank 22.

  The control valves 175 and 176 operate to supply hydraulic oil discharged from the hydraulic pumps 14L and 14R to the boom cylinder 7 as a hydraulic actuator, and to discharge the hydraulic oil in the boom cylinder 7 to the hydraulic oil tank 22, respectively. It is a spool valve that switches the flow of oil. Specifically, the control valve 176 supplies hydraulic oil from the hydraulic pump 14R to the boom cylinder 7 when a boom operation lever as an operation device is operated. In addition, the control valve 175 additionally supplies hydraulic oil from the hydraulic pump 14L to the boom cylinder 7 when the boom operation lever is operated at a predetermined lever operation amount or more.

  The control valves 177 and 178 operate to supply hydraulic oil discharged from the hydraulic pumps 14L and 14R to the arm cylinder 8 as a hydraulic actuator, and to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank 22, respectively. It is a spool valve that switches the flow of oil. Specifically, the control valve 177 supplies hydraulic oil from the hydraulic pump 14L to the arm cylinder 8 when an arm operation lever as an operation device is operated. The control valve 178 additionally supplies hydraulic oil from the hydraulic pump 14R to the arm cylinder 8 when the arm operation lever is operated at a predetermined lever operation amount or more.

  The center bypass pipes 50L and 50R are respectively provided with negative control throttles 20L and 20R between the control valves 177 and 178 and the hydraulic oil tank 22 located on the most downstream side. Hereinafter, the negative control is abbreviated as “negative control”. The negative control throttles 20L and 20R generate a negative control pressure upstream of the negative control throttles 20L and 20R by restricting the flow of hydraulic oil discharged from the hydraulic pumps 14L and 14R.

  The relief valves 19L and 19R are valves that limit the negative control pressure to a predetermined relief pressure or less. In this embodiment, each of the relief valves 19L and 19R is connected in parallel to the negative control throttles 20L and 20R in the center bypass pipes 50L and 50R.

  The pressure sensors S1 and S2 detect the negative control pressure generated upstream of the negative control throttles 20L and 20R, and output the detected value to the controller 30 as an electrical negative control pressure signal. The pressure sensors S3 and S4 detect the discharge pressures of the hydraulic pumps 14L and 14R, and output the detected values to the controller 30 as electrical discharge pressure signals.

  The controller 30 is a functional element that controls the hydraulic system 100. For example, the controller 30 is a computer having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an NVRAM (Non Volatile RAM), and the like. is there.

  In the present embodiment, the controller 30 electrically detects the operation content of various operation devices based on the output of the pilot pressure sensor. The pilot pressure sensor is an example of an operation content detection unit, and measures a pilot pressure generated when various operation devices such as an arm operation lever and a boom operation lever are operated. The operation contents of the various operation devices are, for example, presence / absence of lever operation, lever operation direction, lever operation amount, and the like. The operation content detection unit may be configured using a sensor other than the pilot pressure sensor, such as an inclination sensor that detects the inclination of various operation levers.

  In addition, the controller 30 causes the CPU to execute programs corresponding to various functional elements that operate the electromagnetic valves 55L, 55R and the like according to the operation contents of the various operation devices.

  The electromagnetic valves 55L and 55R are valves that operate according to a command output from the controller 30. In the present embodiment, the electromagnetic valves 55L and 55R adjust the control pressure introduced from the control pump 15 to the pressure receiving chambers 612L and 612R of the discharge amount control units 61L and 61R according to the current command output by the controller 30. It is a valve.

  The pump regulator 40L is a drive mechanism that controls the discharge amount of the hydraulic pump 14L, and mainly includes a tilt actuator 41L, a spool valve mechanism 60L, a discharge amount control unit 61L, and a feedback lever 62L.

  The tilt actuator 41L is a functional element that tilts and drives a swash plate (yoke) for changing the displacement volume (pump capacity) of the hydraulic pump 14L. Specifically, the tilt actuator 41L includes a working piston 410L having a large diameter pressure receiving part PR1 at one end and a small diameter pressure receiving part PR2 at the other end, a pressure receiving chamber 411L corresponding to the large diameter pressure receiving part PR1, and a small diameter pressure receiving part. And a pressure receiving chamber 412L corresponding to the part PR2. The discharge pressure of the hydraulic pump 14L is introduced into the pressure receiving chamber 411L via the spool valve 600L, or the hydraulic oil is discharged from the pressure receiving chamber 411L via the spool valve 600L. The discharge pressure of the hydraulic pump 14L is introduced into the pressure receiving chamber 412L. When the working oil is introduced into the pressure receiving chamber 411L and displaced toward the pressure receiving chamber 412L, the working piston 410L tilts and drives the swash plate (yoke) of the hydraulic pump 14L to the small flow rate side. Further, when the working oil 410L is discharged from the pressure receiving chamber 411L and displaced toward the pressure receiving chamber 411L, the working piston 410L tilts and drives the swash plate (yoke) of the hydraulic pump 14L to the large flow rate side.

  The spool valve mechanism 60L is a functional element for supplying and discharging hydraulic oil to and from the tilt actuator 41L, and includes a spool valve 600L and a spring 601L. The spool valve 600L has a first port into which the discharge pressure of the hydraulic pump 14L is introduced, a second port that communicates with the hydraulic oil tank 22, and an output port that communicates with the pressure receiving chamber 411L. The spool valve 600L has a first position where the first port communicates with the output port, a second position where the second port communicates with the output port, or both the first port and the second port serve as output ports. It is selectively switched to a neutral position that does not communicate. The spring 601L applies a force that acts in a direction to displace the spool valve 600L to the second position.

  The discharge amount control unit 61L is a functional element for displacing the spool valve 600L. Specifically, the discharge amount control unit 61L includes a servo piston 610L, a spring 611L, and a pressure receiving chamber 612L. The servo piston 610L moves in a direction to displace the spool valve 600L to the first position according to the control pressure generated by the electromagnetic valve 55L. The spring 611L applies a force acting in a direction to return the servo piston 610L against the control pressure generated by the electromagnetic valve 55L. The pressure receiving chamber 612L corresponds to the pressure receiving portion PR3 provided in the servo piston 610L, and hydraulic oil is introduced from the control pump 15 through the electromagnetic valve 55L.

  The feedback lever 62L is a link mechanism for feeding back the displacement of the tilting actuator 41L to the spool valve 600L. Specifically, when the operating piston 410L moves, the feedback lever 62L physically feeds back the movement amount to the spool valve 600L to return the spool valve 600L to the neutral position.

  The above description relates to the pump regulator 40L, but the same applies to the pump regulator 40R.

  With the above configuration, the pump regulators 40L and 40R reduce the discharge amount of the hydraulic pumps 14L and 14R as the control pressure introduced into the discharge amount control units 61L and 61R increases. The pump regulators 40L and 40R increase the discharge amounts of the hydraulic pumps 14L and 14R as the control pressure introduced into the discharge amount control units 61L and 61R is smaller.

  FIG. 2 shows a state where none of the hydraulic actuators in the excavator is used. Hereinafter, this state is referred to as “standby mode”. In the standby mode, the hydraulic oil discharged from the hydraulic pumps 14L and 14R passes through the center bypass pipes 50L and 50R to the negative control throttles 20L and 20R, thereby increasing the negative control pressure generated upstream of the negative control throttles 20L and 20R.

  As a result, the pump regulators 40L and 40R displace the spool valves 600L and 600R to the first position in accordance with a command generated by the controller 30 based on the negative control pressure signal. The spool valves 600L and 600R drive the tilting actuators 41L and 41R to reduce the discharge amounts of the hydraulic pumps 14L and 14R. As a result, pressure loss (pumping loss) when hydraulic oil discharged from the hydraulic pumps 14L and 14R passes through the center bypass pipes 50L and 50R is suppressed.

  On the other hand, when one of the hydraulic actuators in the excavator is operated, the hydraulic oil discharged from the hydraulic pumps 14L and 14R flows into the hydraulic actuator via a control valve corresponding to the hydraulic actuator. Therefore, the amount reaching the negative control throttles 20L and 20R decreases or disappears, and the negative control pressure generated upstream of the negative control throttles 20L and 20R decreases.

  As a result, the pump regulators 40L and 40R increase the discharge amount of the hydraulic pumps 14L and 14R, circulate sufficient hydraulic oil to each hydraulic actuator, and ensure the driving of each actuator.

  FIG. 3 is a negative control diagram showing the relationship between the discharge amount of the hydraulic pump 14 (hereinafter referred to as “pump flow rate”) and the negative control pressure, with the pump flow rate on the vertical axis and the negative control pressure on the horizontal axis. Arrange. As described above, the pump control line represented by the solid line shows a tendency that the pump flow rate increases as the negative control pressure decreases. Note that FIG. 3 omits the illustration of the relationship between the negative control pressure and the pump flow rate in the standby mode. However, in practice, when the negative control pressure is lower than the predetermined pressure in the standby mode, the pump flow rate is limited to the minimum flow rate.

  Hereinafter, the control of the pump flow rate based on the negative control pressure as described above is referred to as “negative control”. With the negative control, the hydraulic system 100 can suppress wasteful energy consumption in the standby mode. This is because the hydraulic oil discharged from the hydraulic pumps 14L and 14R can suppress the pumping loss generated in the center bypass pipes 50L and 50R. Further, when operating various hydraulic actuators, the hydraulic system 100 can supply necessary and sufficient hydraulic fluid from the hydraulic pumps 14L and 14R to the various hydraulic actuators.

  The hydraulic system 100 executes horsepower control in parallel with the negative control. The horsepower control is a control for reducing the pump flow rate in accordance with an increase in the discharge pressure of the hydraulic pump 14 (hereinafter referred to as “pump discharge pressure”) so that the absorption horsepower of the hydraulic pump 14 does not exceed the output horsepower of the engine. is there.

  FIG. 4 is a horsepower control diagram (PQ diagram) showing the relationship between the pump flow rate and the pump discharge pressure, where the vertical axis represents the pump flow rate and the horizontal axis represents the pump discharge pressure. The horsepower control line represented by a solid line shows a tendency that the pump flow rate increases as the pump discharge pressure decreases.

  Next, a turning hydraulic circuit 200 constituting a part of the hydraulic system 100 mounted on the excavator of FIG. 1 will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a configuration example of the swing hydraulic circuit 200.

  As shown in FIG. 5, the swing hydraulic circuit 200 mainly includes a swing hydraulic motor 21, swing relief valves 71L and 71R, and check valves 72L and 72R.

  The turning hydraulic motor 21 turns the upper turning body 3 through a turning mechanism including a mechanical brake 80 and a speed reducer 81. In the present embodiment, the output torque of the turning hydraulic motor 21 is amplified by a speed reducer 81 configured by a two-stage planetary gear mechanism. The rotation of the output shaft of the turning hydraulic motor 21 is braked by a mechanical brake 80 including a plurality of brake disks and a plurality of brake plates sandwiching each brake disk.

  Further, the first port 21L of the turning hydraulic motor 21 is connected to the first port P1 of the control valve 173 via the pipeline 70L, and the second port 21R of the turning hydraulic motor 21 is connected via the pipeline 70R. And connected to the second port P2 of the control valve 173.

  The swing relief valves 71L and 71R are valves that limit the pressure of hydraulic oil in the pipe lines 70L and 70R (hereinafter referred to as “swing hydraulic circuit internal pressure”) to a predetermined swing relief pressure or less. In the present embodiment, the swing relief valves 71L and 71R may be fixed relief valves in which the swing relief pressure is fixedly set by a spring or the like.

  Specifically, the swing relief valve 71L is partially opened when the internal pressure of the swing hydraulic circuit in the pipe line 70L reaches the cracking pressure, and the hydraulic oil in the pipe line 70L passes through the pipe line 73. The outflow to the tank 22 is started. Further, the swing relief valve 71L is fully opened when the internal pressure of the swing hydraulic circuit in the pipe 70L reaches the swing relief pressure, and the swing relief valve 71L operates in the pipe 70L so that the internal pressure of the swing hydraulic circuit does not excessively exceed the swing relief pressure. Oil flows out to the hydraulic oil tank 22. Similarly, the swing relief valve 71R is partially opened when the internal pressure of the swing hydraulic circuit of the pipe line 70R reaches the cracking pressure, and the hydraulic oil tank 22 of the hydraulic oil in the pipe line 70R via the pipe line 73 is opened. Let the spill begin. Further, the swing relief valve 71R is fully opened when the internal pressure of the swing hydraulic circuit in the pipeline 70R reaches the swing relief pressure, and the swing relief valve 71R operates in the pipeline 70R so that the internal pressure of the swing hydraulic circuit does not excessively exceed the swing relief pressure. Oil flows out to the hydraulic oil tank 22.

  The pressure sensors S7L and S7R detect the internal pressure of the swing hydraulic circuit and output the detected value to the controller 30 as an electrical swing hydraulic circuit internal pressure signal. Specifically, the pressure sensor S7L determines the pressure of the hydraulic oil in the pipe line 70L when the hydraulic oil is driven into the first port 21L of the hydraulic hydraulic motor 21 to drive the hydraulic hydraulic motor 21. Detect as internal pressure. Further, the pressure sensor S7R detects the pressure of the hydraulic oil in the pipe line 70R as the internal pressure of the turning hydraulic circuit when the hydraulic oil is driven into the second port 21R of the turning hydraulic motor 21 to drive the turning hydraulic motor 21. To do.

  The tilt angle sensor S8 is a sensor that detects the tilt angle of the swash plate of the hydraulic pump 14L, and outputs the detected value to the controller 30. The turning angular velocity sensor S <b> 9 is a sensor that detects the turning angular velocity of the upper swing body 3, and outputs the detected value to the controller 30.

  FIG. 6 is a diagram showing the relationship between the internal pressure of the swing hydraulic circuit and the flow rate of hydraulic oil that passes through the swing relief valve 71 (hereinafter referred to as “swing relief flow rate”).

  As shown in FIG. 6, the turning relief flow rate is zero when the turning hydraulic circuit internal pressure is less than the cracking pressure Pc. In addition, when the swing hydraulic circuit internal pressure is equal to or higher than the cracking pressure Pc and lower than the swing relief pressure Pr, the swing relief flow rate increases relatively gradually as the swing hydraulic circuit internal pressure increases. Further, when the swing hydraulic circuit internal pressure is equal to or higher than the swing relief pressure Pr, the swing relief flow rate increases relatively rapidly as the swing hydraulic circuit internal pressure increases.

  The check valves 72L and 72R are valves that prevent the pressure of the hydraulic oil in the pipelines 70L and 70R from dropping below the pressure of the hydraulic oil in the hydraulic oil tank 22 (hereinafter referred to as “tank pressure”).

  Specifically, the check valve 72L is opened when the internal pressure of the turning hydraulic circuit in the pipeline 70L becomes less than the tank pressure while prohibiting the hydraulic oil in the pipeline 70L from flowing out to the hydraulic oil tank 22. Then, the hydraulic oil in the hydraulic oil tank 22 (pipe line 73) is caused to flow into the pipe line 70L. Similarly, the check valve 72R is in an open state when the hydraulic pressure in the turning hydraulic circuit in the pipe line 70R becomes less than the tank pressure while prohibiting the hydraulic oil in the pipe line 70R from flowing out to the hydraulic oil tank 22, and the check valve 72R operates. The hydraulic oil in the oil tank 22 (pipe 73) is caused to flow into the pipe 70R.

  The main relief valve 83 is a valve that limits the pressure of the hydraulic oil in the hydraulic system 100 to a predetermined main relief pressure or less. In the present embodiment, the main relief valve 83 is a fixed relief valve in which the main relief pressure is fixedly set by a spring or the like. The main relief pressure is set to be higher than the turning relief pressure.

  In this embodiment, the contents of the turning operation including the presence / absence of the turning operation are derived based on the outputs of the pressure sensors S5 and S6. The pressure sensors S5 and S6 are pilot pressure sensors that detect a pilot pressure corresponding to a lever operation amount of the turning operation lever 82 (hereinafter referred to as a “turning lever operation amount”). The pump discharge pressure of the hydraulic pump 14L is derived based on the output of the pressure sensor S3 as a discharge pressure sensor.

  For example, when the turning operation lever 82 is operated in the right turning direction and the pilot pressure detected by the pressure sensor S6 increases, the control valve 173 is moved in the left direction. At this time, the control valve 173 communicates the hydraulic pump 14L with the first port 21L of the turning hydraulic motor 21 through the first port P1, and the second port 21R of the turning hydraulic motor 21 through the second port P2. The hydraulic oil tank 22 is connected. Further, the control valve 173 reduces or eliminates the flow rate of the hydraulic oil that reaches the negative control throttle 20L (see FIG. 2) through the center bypass pipe line 50L. As a result, the negative control pressure decreases, and the hydraulic pump 14L increases the pump flow rate as shown in the negative control chart of FIG.

  On the other hand, the amount of hydraulic oil consumed for driving the turning hydraulic motor 21 (hereinafter referred to as “turning consumption flow rate”) gradually increases while being lower than the pump flow rate of the hydraulic pump 14L. This is because the upper swing body 3 of the shovel has a large moment of inertia. At this time, at least a part of the hydraulic oil discharged from the hydraulic pump 14L is discharged to the hydraulic oil tank 22 via the turning relief valve 71L. Therefore, a part of the hydraulic energy generated by the hydraulic pump 14L is wasted without being used.

  Therefore, in order to control the turning torque while minimizing the wasteful hydraulic energy, the controller 30 reduces the internal pressure of the turning hydraulic circuit below the cracking pressure of the turning relief valve 71 when a turning operation is performed. The process of adjusting to the predetermined pressure (hereinafter referred to as “swing hydraulic circuit internal pressure adjustment process”) is executed. In this embodiment, the controller 30 adjusts the internal pressure of the swing hydraulic circuit to a predetermined pressure lower than the cracking pressure by increasing or decreasing the displacement volume of the hydraulic pump 14L to control the swing torque.

  Here, a configuration example of a control system employed when executing the turning hydraulic circuit internal pressure adjustment processing will be described with reference to FIG. FIG. 7 is a functional block diagram illustrating a configuration example of the control system.

  Specifically, the control system of FIG. 7 includes a controller 30, an attitude detection unit E30, a displacement displacement detection unit E31, a turning hydraulic circuit internal pressure detection unit E32, and a turning angular velocity detection unit E33. The controller 30 includes a model prediction control unit 34 and a horsepower control unit 35.

  The posture detection unit E30 is a functional element that detects the posture of the attachment. In this embodiment, the posture detection unit E30 is a posture detection device M1 that detects the posture of the excavation attachment. The attitude detection device M1 acquires the position (bucket position) Bp of the bucket 6 as an end attachment based on the detected boom angle, arm angle, bucket angle, and airframe tilt angle, and uses the value as an electrical end attachment position. It outputs to the model prediction control part 34 as a signal.

  The displacement volume detector E31 is a functional element that detects the displacement volume Vd of the hydraulic pump 14L. In this embodiment, the displacement volume detection unit E31 is a tilt angle sensor S8 that detects the tilt angle of the swash plate of the hydraulic pump 14L. The tilt angle sensor S8 acquires the displacement volume based on the detected swash plate tilt angle, and outputs the displacement volume as an electrical displacement volume signal to the model prediction control unit 34. Note that the displacement volume detection unit E31 may calculate the displacement volume from the previous displacement volume command value Vt and output the value to the model prediction control unit 34 as an electrical displacement volume signal.

  The swing hydraulic circuit internal pressure detector E32 is a functional element that detects the swing hydraulic circuit internal pressure. In the present embodiment, the swing hydraulic circuit internal pressure detection unit E32 is pressure sensors S7L and S7R that detect the swing hydraulic circuit internal pressure Pm, and outputs the detected values to the model prediction control unit 34.

  The turning hydraulic circuit internal pressure Pm is the pressure of the hydraulic oil in the pipelines 70L and 70R. In the present embodiment, the controller 30 obtains the output of the pressure sensor S7R as the turning hydraulic circuit internal pressure Pm when the left turn operation is performed, and turns the output of the pressure sensor S7L when the right turn operation is performed. Obtained as the hydraulic circuit internal pressure Pm.

  The turning angular velocity detection unit E33 is a functional element that detects the turning angular velocity. In this embodiment, the turning angular velocity detection unit E33 is a turning angular velocity sensor S9 that detects the turning angular velocity ω of the upper turning body 3. The turning angular velocity sensor S9 is a rotary encoder, for example, and outputs the detected value to the model prediction control unit 34 as an electric turning angular velocity signal.

  The model prediction control unit 34 is a functional element that performs control (model prediction control) based on the optimal control theory in real time using a model that predicts the behavior of the swing hydraulic circuit including the hydraulic pump 14L and the swing hydraulic motor 21. The model predictive control of the swing hydraulic circuit is control using a plant model of the swing hydraulic circuit. The plant model of the swing hydraulic circuit is a model that can derive the output of the swing hydraulic circuit from the input to the swing hydraulic circuit. In the present embodiment, the model prediction control unit 34 calculates the turning angular velocity ω, the turning hydraulic circuit internal pressure Pm, the displacement volume Vd of the hydraulic pump 14L, the target turning hydraulic circuit internal pressure Pt, and the previous displacement volume command value Vt. The predicted value of the internal pressure of the swing hydraulic circuit in the future within a finite time can be derived.

  The target swing hydraulic circuit internal pressure Pt is a pressure value lower than the cracking pressure Pc, and is stored in advance in NVRAM or the like. In this embodiment, the target swing hydraulic circuit internal pressure Pt is stored in association with the swing lever operation amount. Specifically, the target turning hydraulic circuit internal pressure Pt is set so as to increase as the turning lever operation amount increases. When the turning operation lever 82 is operated, the controller 30 reads the target turning hydraulic circuit internal pressure Pt corresponding to the turning lever operation amount from the NVRAM. Further, the controller 30 may adjust the target turning hydraulic circuit internal pressure Pt according to the bucket position Bp from the attitude detection unit E30.

  Specifically, the model prediction control unit 34 derives a predicted value of the internal pressure of the swing hydraulic circuit using the following matrix equation representing the state of the swing hydraulic circuit. A and B are coefficient matrices representing structural features of the swing hydraulic circuit.

具体的には、モデル予測制御部３４は、現時点における旋回角速度ω、旋回油圧回路内圧Ｐｍ、及び押し退け容積Ｖｄと前回の押し退け容積指令値Ｖｔとに基づいて旋回角速度ω、旋回油圧回路内圧Ｐｍ、及び押し退け容積Ｖｄのそれぞれの微分値を導き出す。そして、現時点における旋回角速度ωにその微分値を加算して算出対象である所定時間後の旋回角速度の予測値ω'を導き出す。旋回油圧回路内圧Ｐｍ及び押し退け容積Ｖｄについても同様にして所定時間後の旋回油圧回路内圧の予測値Ｐｍ'及び所定時間後の押し退け容積の予測値Ｖｄ'を導き出す。

Specifically, the model prediction control unit 34 determines the turning angular velocity ω, the turning hydraulic circuit internal pressure Pm, the turning angular velocity ω, the turning hydraulic circuit internal pressure Pm, and the displacement volume Vd and the previous displacement volume command value Vt. And the respective differential values of the displacement volume Vd are derived. Then, the differential value is added to the current turning angular velocity ω to derive the predicted turning angular velocity ω ′ after a predetermined time, which is a calculation target. Similarly, for the swing hydraulic circuit internal pressure Pm and the displacement volume Vd, the predicted value Pm ′ of the swing hydraulic circuit pressure after a predetermined time and the predicted value Vd ′ of the displacement volume after a predetermined time are derived.

  Similarly, the model prediction control unit 34 turns the turning angular velocity and turning hydraulic circuit after a predetermined time when each of the plurality of displacement volume command values set based on the previous displacement volume command value Vt is continuously used. The predicted values of the internal pressure and displacement volume are derived by the method described above.

  After that, the model prediction control unit 34 selects the displacement displacement command value Vtc that minimizes the difference between the target swing hydraulic circuit internal pressure Pt and the predicted value of the swing hydraulic circuit internal pressure after a predetermined time, which is a calculation target. Specifically, one of a plurality of displacement volume command values including the previous displacement volume command value Vt is selected as the displacement volume command value Vtc to be adopted this time.

  The model prediction control unit 34 then outputs the selected displacement volume command value Vtc to the horsepower control unit 35.

  The horsepower control unit 35 controls the displacement volume of the hydraulic pump 14L using the displacement volume command value Vtc selected by the model prediction control unit 34.

  Next, a time transition of the turning hydraulic circuit internal pressure Pm when the turning operation lever 82 is operated will be described with reference to FIG. FIG. 8 is a diagram showing temporal transition of the internal pressure of the swing hydraulic circuit and the amount of operation of the swing lever. Further, a broken line in FIG. 8 shows a temporal transition when the feedback control system is adopted, and a solid line in FIG. 8 shows a temporal transition when the control system in FIG. 7 is adopted. The feedback control system as a comparison target generates a displacement volume command value Vt so that the deviation between the target swing hydraulic circuit internal pressure Pt and the current swing hydraulic circuit internal pressure Pm is close to zero, and sets the displacement volume command value Vt to the displacement volume command value Vt. Accordingly, this is a system for controlling the displacement volume Vd of the hydraulic pump 14L.

  When the feedback control system is employed, the turning hydraulic circuit internal pressure Pm starts to increase when the turning lever 82 is fully operated at time t1. This is because the hydraulic oil discharged from the hydraulic pump 14L flows into the swing hydraulic circuit. Note that the full lever operation refers to a state in which the neutral operation state of the turning operation lever 82 is operated with an operation amount of 80% or more when the operation amount is 0% and the maximum operation state is 100%.

  Specifically, the swing hydraulic circuit internal pressure Pm increases after exceeding the target swing hydraulic circuit internal pressure Pt, then turns to decrease at time t2, and then decreases until it falls below the target swing hydraulic circuit internal pressure Pt, at time t3. It starts to increase again. Thereafter, while the full lever operation is continued, the swing hydraulic circuit internal pressure Pm changes within a predetermined pressure range having the target swing hydraulic circuit internal pressure Pt as a median value while repeatedly increasing and decreasing across the target swing hydraulic circuit internal pressure Pt.

  In this manner, the controller 30 increases or decreases the displacement volume command value, and controls the swing hydraulic circuit internal pressure Pm by feedback control so that the target swing hydraulic circuit internal pressure Pt is less than the cracking pressure Pc of the swing relief valve 71. Therefore, the usable range of the magnitude of the turning torque represented by the product of the turning hydraulic circuit internal pressure Pm and the turning consumption flow rate can be expanded. Specifically, a turning torque smaller than the turning torque obtained when hydraulic oil having a pressure equal to or higher than the cracking pressure Pc can be used.

  In the case where the control system of FIG. 7 is adopted, when the full lever operation of the turning operation lever 82 is performed at time t1, the turning hydraulic circuit internal pressure Pm starts to increase as in the case where the feedback control system is adopted. This is because the hydraulic oil discharged from the hydraulic pump 14L flows into the swing hydraulic circuit.

  However, when the control system of FIG. 7 is adopted, unlike the case where the feedback control system is adopted, the turning hydraulic circuit internal pressure Pm does not greatly exceed the target turning hydraulic circuit internal pressure Pt, and the target turning hydraulic circuit at time t10. The internal pressure Pt is reached. Then, after reaching the target swing hydraulic circuit internal pressure Pt, the target swing hydraulic circuit internal pressure Pt is maintained. This is because, by the model predictive control, the displacement hydraulic pressure command value is changed before the swing hydraulic circuit internal pressure Pm exceeds the target swing hydraulic circuit internal pressure Pt, and the increase of the swing hydraulic circuit internal pressure Pm is proactively suppressed. Further, after the swing hydraulic circuit internal pressure Pm reaches the target swing hydraulic circuit internal pressure Pt, the displacement command value is changed before the swing hydraulic circuit internal pressure Pm deviates from the target swing hydraulic circuit internal pressure Pt by model predictive control. This is because the deviation of the hydraulic circuit internal pressure Pm is proactively suppressed.

  In this manner, the controller 30 increases or decreases the displacement command value, and controls the swing hydraulic circuit internal pressure Pm by model predictive control so that the target swing hydraulic circuit internal pressure Pt is less than the cracking pressure Pc of the swing relief valve 71. Therefore, the usable range of the magnitude of the turning torque represented by the product of the turning hydraulic circuit internal pressure Pm and the turning consumption flow rate can be expanded. Specifically, a turning torque smaller than the turning torque obtained when hydraulic oil having a pressure equal to or higher than the cracking pressure Pc can be used.

  Further, the control system of FIG. 7 can reduce the influence of the response delay of the hydraulic pump 14L with respect to the load fluctuation, compared with the feedback control system. Therefore, the turning torque can be controlled more stably by maintaining the turning hydraulic circuit internal pressure Pm more stably at the target turning hydraulic circuit internal pressure Pt.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

  For example, in the above-described embodiment, the controller 30 or the model prediction control unit 34 employs the output of the pressure sensors S7L and S7R as the turning hydraulic circuit internal pressure Pm, but the pump discharge pressure of the hydraulic pump 14L that is the output of the pressure sensor S3. May be adopted as the turning hydraulic circuit internal pressure Pm.

  Further, in the above-described embodiment, the model prediction control unit 34 has been described as being integrated with the controller 30, but may be separate from the controller 30.

  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 cylinders 14L, 14R ... Hydraulic pump 15 ... Control pumps 19L, 19R ... Relief valves 20L, 20R ... Negacon throttle 21 ... Hydraulic hydraulic motor 21L ... First port 21R .. second port 22 ... hydraulic oil tank 30 ... controller 34 ... model prediction control unit 35 ... horsepower control unit 40L, 40R ... pump regulator 41L, 41R ... tilt actuator 42L , 42R: traveling hydraulic motors 50L, 50R: center bypass pipes 55L, 55R: solenoid valves 60L, 6 R ... Spool valve mechanism 61L, 61R ... Discharge amount control unit 70L, 70R, 73 ... Pipe line 71L, 71R ... Swing relief valve 72L, 72R ... Check valve 80 ... Mechanical brake DESCRIPTION OF SYMBOLS 81 ... Reduction gear 82 ... Turning control lever 83 ... Main relief valve 100 ... Hydraulic system 170-178 ... Control valve 200 ... Turning hydraulic circuit E30 ... Attitude detection part E31. ..Push-off volume detection unit E32 ... Swivel hydraulic circuit internal pressure detection unit E33 ... Turning angular velocity detection unit P1 ... First port P2 ... Second port S1-S6, S7L, S7R ... Pressure sensor

Claims (7)

A turning hydraulic motor;
A variable displacement hydraulic pump for supplying hydraulic oil to the turning hydraulic motor;
A turning relief valve disposed in a pipe line connecting the turning hydraulic motor and the hydraulic pump;
A controller for controlling the turning torque of the turning hydraulic motor,
The controller controls the turning torque of the turning hydraulic motor by adjusting the turning hydraulic circuit internal pressure to a predetermined pressure lower than the cracking pressure of the turning relief valve by increasing or decreasing the displacement of the hydraulic pump.
Excavator. Provided with a swing hydraulic circuit internal pressure detection unit for detecting the internal pressure of the swing hydraulic circuit,
The controller increases or decreases the displacement volume of the hydraulic pump according to the swing hydraulic circuit internal pressure detected by the swing hydraulic circuit internal pressure detector.
The excavator according to claim 1. The relief pressure of the swing relief valve is fixed,
The shovel according to claim 1 or 2. The controller feedback-controls the displacement volume of the hydraulic pump according to a displacement volume command value generated based on a deviation between a target swing hydraulic circuit internal pressure and a current swing hydraulic circuit internal pressure;
The excavator according to any one of claims 1 to 3. A model prediction control unit that predicts the turning hydraulic circuit internal pressure after a predetermined time when using a plurality of displacement displacement command values,
The model prediction control unit selects a displacement volume command value that minimizes a difference between the current swing hydraulic circuit internal pressure and the swing hydraulic circuit internal pressure after a predetermined time from the plurality of displacement volume command values,
The controller controls the displacement volume of the hydraulic pump by model prediction control using the displacement volume command value selected by the model prediction control unit.
The excavator according to any one of claims 1 to 4.   The controller predicts the behavior of the swing hydraulic circuit after a predetermined time, and adjusts the internal pressure of the swing hydraulic circuit to a predetermined pressure less than the cracking pressure of the swing relief valve by increasing or decreasing the displacement of the hydraulic pump based on the predicted value. ,
  The excavator according to any one of claims 1 to 4.   An upper swing body,
  An attachment provided in the upper swing body;
  A posture detecting device for detecting the posture of the attachment;
  The excavator according to any one of claims 1 to 6.

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