JP2021021199A - Shovel - Google Patents

Abstract

To smoothen movement of a hydraulic actuator when a load applied to the hydraulic actuator during operation of the hydraulic actuator varies.SOLUTION: A shovel 100 comprises an attachment, hydraulic actuators, main pumps 14, oil passages 42 for supplying working oil discharged from the main pumps 14 to multiple hydraulic actuators, multiple control valves 171-176 arranged to the oil passages 42, and control valves 177 as bleed valves arranged to the oil passages 42. The shovel 100 is configured to control openings of the control valves 177 according to a load applied to the hydraulic actuators.SELECTED DRAWING: Figure 3

Description

This disclosure relates to excavators.

Conventionally, an excavator provided with a plurality of control valves (spool valves) corresponding to a plurality of hydraulic actuators is known (see Patent Document 1). In this excavator, for example, the spool valve corresponding to the arm cylinder operates according to the lever operation amount of the arm operation lever, and is configured so that the opening areas of the PT port, the PC port, and the CT port can be adjusted at the same time. ing. The PT port is a port that forms a part of an oil passage that connects the hydraulic pump and the hydraulic oil tank. The flow rate of the hydraulic oil passing through the PT port corresponds to the bleed flow rate of the hydraulic oil discharged by the hydraulic pump, which is the flow rate of the hydraulic oil discharged to the hydraulic oil tank without passing through the hydraulic actuator. The PC port is a port that forms a part of an oil passage that connects the hydraulic pump and the arm cylinder. The CT port is a port that forms a part of an oil passage that connects the arm cylinder and the hydraulic oil tank.

Japanese Unexamined Patent Publication No. 2012-21015

However, in the above-mentioned excavator, the spool valve corresponding to the arm cylinder is configured so that the opening areas of the PT port, the PC port, and the CT port are uniquely determined once the lever operating amount of the arm operating lever is determined. There is. That is, the spool valve corresponding to the arm cylinder is not configured so that the opening area of the PT port can be changed regardless of the opening area of the PC port. Specifically, in the spool valve corresponding to the arm cylinder, the larger the lever operating amount of the arm operating lever, the larger the opening area of the PC port and the opening area of the CT port, and the smaller the opening area of the PT port. It is configured to be.

Therefore, when the pressure of the hydraulic oil in the arm cylinder corresponding to the load applied to the arm cylinder increases, it is the flow rate of the hydraulic oil discharged from the hydraulic pump to the hydraulic oil tank through the PT port. The bleed flow rate will increase. As a result, even when it is required to maintain the flow rate of the hydraulic oil flowing into the arm cylinder, that is, even when the continuous operation of the arm is required, the flow rate of the hydraulic oil flowing into the arm cylinder through the PC port. Will drop. As a result, the movement of the arm slows down or stops. In this case, the operator cannot maintain the flow rate of the hydraulic oil flowing into the arm cylinder unless the lever operating amount of the arm operating lever is increased. However, even when the lever operating amount of the arm operating lever is increased, the operator cannot predict an appropriate lever operating amount, so that the movement of the arm may become unstable. For example, the operator may excessively increase the amount of lever operation and unintentionally move the arm suddenly.

In view of the above problems, it is desirable to provide an excavator that smoothes the movement of the hydraulic actuator when the load applied to the hydraulic actuator changes during the operation of the hydraulic actuator.

The excavator according to the embodiment of the present invention is arranged in the attachment, the hydraulic actuator, the hydraulic pump, the oil passage capable of supplying the hydraulic oil discharged by the hydraulic pump to the plurality of the hydraulic actuators, and the oil passage. It has a plurality of control valves and a bleed valve arranged in the oil passage, and adjusts the opening of the bleed valve according to a load applied to the hydraulic actuator.

The excavator described above can smooth the movement of the hydraulic actuator when the load applied to the hydraulic actuator changes during the operation of the hydraulic actuator.

It is a side view of the structural example of the excavator which concerns on embodiment of this invention. It is a figure which shows the configuration example of the drive system mounted on the excavator shown in FIG. It is a figure which shows the structural example of the hydraulic system mounted on the excavator shown in FIG. It is a flowchart of an example of an adjustment process. It is a left side view of the excavation attachment which performs the slope formation work. It is a figure which shows the time transition of the arm bottom pressure, the opening area of a bleed valve, the bleed flow rate, and the actuator flow rate. It is a side view of another structural example of the excavator which concerns on embodiment of this invention. It is a figure which shows the structural example of the hydraulic system mounted on the excavator shown in FIG. 7. It is a flowchart of another example of the adjustment process. It is a figure which shows the time transition of the arm closing speed, the opening area of a bleed valve, the bleed flow rate, and the actuator flow rate. It is a figure which shows the configuration example of an electric operation system.

FIG. 1 is a side view of an excavator (excavator 100) according to an embodiment of the present invention. An upper swivel body 3 is mounted on the lower traveling body 1 of the excavator 100 so as to be swivelable via a swivel mechanism 2. A boom 4 is attached to the upper swing body 3. An arm 5 is attached to the tip of the boom 4. A bucket 6 as an end attachment is attached to the tip of the arm 5.

The boom 4, arm 5, and bucket 6 form an excavation attachment as an example of the attachment. The boom 4 is driven by the boom cylinder 7, the arm 5 is driven by the arm cylinder 8, and the bucket 6 is driven by the bucket cylinder 9.

A boom rod pressure sensor S7R and a boom bottom pressure sensor S7B are attached to the boom cylinder 7. An arm rod pressure sensor S8R and an arm bottom pressure sensor S8B are attached to the arm cylinder 8. A bucket rod pressure sensor S9R and a bucket bottom pressure sensor S9B are attached to the bucket cylinder 9.

The boom rod pressure sensor S7R detects the pressure of hydraulic oil in the rod side oil chamber of the boom cylinder 7 (hereinafter referred to as “boom rod pressure”), and the boom bottom pressure sensor S7B detects the oil on the bottom side of the boom cylinder 7. The pressure of hydraulic oil in the chamber (hereinafter referred to as "boom bottom pressure") is detected. The arm rod pressure sensor S8R detects the pressure of hydraulic oil in the rod side oil chamber of the arm cylinder 8 (hereinafter referred to as “arm rod pressure”), and the arm bottom pressure sensor S8B detects the oil on the bottom side of the arm cylinder 8. The pressure of hydraulic oil in the chamber (hereinafter referred to as "arm bottom pressure") is detected. The bucket rod pressure sensor S9R detects the pressure of hydraulic oil in the rod side oil chamber of the bucket cylinder 9 (hereinafter referred to as "bucket rod pressure"), and the bucket bottom pressure sensor S9B detects the bottom side oil of the bucket cylinder 9. The pressure of hydraulic oil in the chamber (hereinafter referred to as "bucket bottom pressure") is detected.

The upper swing body 3 is provided with a cabin 10 which is an driver's cab and is equipped with a power source such as an engine 11. Further, an airframe tilt sensor S4, a swivel angular velocity sensor S5, and a camera S6 are attached to the upper swivel body 3.

The body tilt sensor S4 is configured to detect the tilt of the upper swing body 3. In the present embodiment, the airframe tilt sensor S4 is an acceleration sensor that detects the tilt angles around the front-rear axis and the left-right axis of the upper swivel body 3 with respect to the horizontal plane. The front-rear axis and the left-right axis of the upper swivel body 3 pass through the excavator center point, which is one point on the swivel axis of the excavator 100, orthogonal to each other.

The turning angular velocity sensor S5 is configured to detect the turning angular velocity of the upper swinging body 3. In the present embodiment, the turning angular velocity sensor S5 is a gyro sensor. The turning angular velocity sensor S5 may be a resolver, a rotary encoder, or the like.

The camera S6 is configured to acquire an image of the periphery of the excavator 100. In the present embodiment, the camera S6 includes a front camera attached to the upper swing body 3. The front camera is a stereo camera that captures the front of the excavator 100, and is mounted on the roof of the cabin 10, that is, outside the cabin 10. The front camera may be mounted on the ceiling of the cabin 10, that is, inside the cabin 10. The front camera can image the excavation attachment. The front camera may be a monocular camera.

A controller 30 is installed in the cabin 10. The controller 30 is configured to function as a main control unit that controls the drive of the excavator 100. In the present embodiment, the controller 30 is composed of a computer including a CPU, RAM, ROM, and the like. Various functions of the controller 30 are realized by the CPU executing the program stored in the ROM.

FIG. 2 is a block diagram showing a configuration example of the drive system mounted on the excavator 100 shown in FIG. 1, and the mechanical power transmission line, hydraulic oil line, pilot line, and electric control line are double-lined and solid-lined, respectively. , Dotted line, and alternate long and short dash line.

The drive system of the excavator 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operating device 26, a discharge pressure sensor 28, an operating pressure sensor 29, a controller 30, a solenoid valve 31, and the like. including.

The engine 11 is a drive source for the excavator 100. In the present embodiment, the engine 11 is, for example, a diesel engine that operates so as to maintain a predetermined rotation speed. Further, the output shaft of the engine 11 is connected to each input shaft of the main pump 14 and the pilot pump 15.

The main pump 14 is configured to supply hydraulic oil to the control valve 17 via a hydraulic oil line. In the present embodiment, the main pump 14 is a swash plate type variable displacement hydraulic pump.

The regulator 13 is configured to control the discharge amount of the main pump 14. In the present embodiment, the regulator 13 controls the discharge amount of the main pump 14 by adjusting the swash plate tilt angle of the main pump 14 in response to a control command from the controller 30.

The pilot pump 15 is configured to supply hydraulic oil to various hydraulic control devices including an operating device 26 and a solenoid valve 31 via a pilot line. In the present embodiment, the pilot pump 15 is a fixed displacement hydraulic pump. However, the pilot pump 15 may be omitted. In this case, the function carried out by the pilot pump 15 may be realized by the main pump 14. That is, the main pump 14 has a function of supplying the hydraulic oil to the operating device and the like after reducing the pressure of the hydraulic oil by a throttle or the like, in addition to the function of supplying the hydraulic oil to the control valves 171 to 177. May be good.

The control valve 17 is a flood control device that controls the flood control system in the excavator 100. The control valve 17 includes control valves 171 to 177. The control valve 17 can selectively supply the hydraulic oil discharged from the main pump 14 to one or a plurality of hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 are configured to control the flow rate of the hydraulic oil flowing from the main pump 14 to the hydraulic actuator and the flow rate of the hydraulic oil flowing from the hydraulic actuator to the hydraulic oil tank. The hydraulic actuator includes a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left traveling hydraulic motor 1A, a right traveling hydraulic motor 1B, and a turning hydraulic motor 2A. The control valve 177 functions as a bleed valve that controls the flow rate of the hydraulic oil (hereinafter referred to as “bleed flow rate”) that flows to the hydraulic oil tank without passing through the hydraulic actuator among the hydraulic oil discharged by the main pump 14. It is configured to do. The control valve 177 may be installed outside the control valve 17.

The operating device 26 is a device used by the operator to operate the hydraulic actuator. In the present embodiment, the operating device 26 supplies the hydraulic oil discharged by the pilot pump 15 to the pilot ports of the control valves corresponding to the respective hydraulic actuators via the pilot line. The pressure of the hydraulic oil (pilot pressure) supplied to each of the pilot ports is a pressure corresponding to the operation direction and the operation amount of the operation device 26 corresponding to each of the hydraulic actuators.

The discharge pressure sensor 28 is configured to detect the discharge pressure of the main pump 14. In the present embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

The operating pressure sensor 29 is configured to detect the operation content of the operating device 26. In the present embodiment, the operating pressure sensor 29 detects the operating direction and operating amount of the operating device 26 corresponding to each of the hydraulic actuators in the form of pressure (operating pressure), and outputs the detected value to the controller 30. .. The operation content of the operation device 26 may be detected by using a sensor other than the operation pressure sensor.

The solenoid valve 31 is configured to operate in response to a control command output by the controller 30. In the present embodiment, the solenoid valve 31 is a pilot of the control valve 177 brought about by hydraulic oil introduced from the pilot pump 15 to the pilot port of the control valve 177 in the control valve 17 in response to a current command output from the controller 30. It is a solenoid proportional valve that adjusts the pressure (pilot pressure) acting on the port. The solenoid valve 31 operates so that, for example, the larger the current command value, the larger the pilot pressure acting on the pilot port of the control valve 177.

Next, a configuration example of the hydraulic system mounted on the excavator 100 will be described with reference to FIG. FIG. 3 is a schematic view showing a configuration example of a hydraulic system mounted on the excavator 100 shown in FIG. Similar to FIG. 2, FIG. 3 shows the mechanical power transmission line, hydraulic oil line, pilot line, and electric control line as double-dashed lines, solid lines, dotted lines, and alternate-dotted lines, respectively.

The hydraulic system shown in FIG. 3 circulates hydraulic oil from the main pump 14 driven by the engine 11 to the hydraulic oil tank via the oil passage 42. The main pump 14 includes a left main pump 14L and a right main pump 14R.

The oil passage 42 includes a left oil passage 42L and a right oil passage 42R. The left oil passage 42L is a hydraulic oil line that connects each of the control valves 171, 173, 175L, and 176L arranged in the control valve 17 in parallel between the left main pump 14L and the hydraulic oil tank. The right oil passage 42R is a hydraulic oil line that connects the control valves 172, 174, 175R, and 176R arranged in the control valve 17 in parallel between the right main pump 14R and the hydraulic oil tank.

The control valve 171 supplies the hydraulic oil discharged by the left main pump 14L to the left traveling hydraulic motor 1A, and discharges the hydraulic oil discharged by the left traveling hydraulic motor 1A to the hydraulic oil tank. A spool valve that switches the flow.

The control valve 172 supplies the hydraulic oil discharged by the right main pump 14R to the right traveling hydraulic motor 1B, and discharges the hydraulic oil discharged by the right traveling hydraulic motor 1B to the hydraulic oil tank. A spool valve that switches the flow.

The control valve 173 supplies the hydraulic oil discharged by the left main pump 14L to the swivel hydraulic motor 2A, and discharges the hydraulic oil discharged by the swivel hydraulic motor 2A to the hydraulic oil tank. It is a spool valve that switches.

A left turning pressure sensor S2L and a right turning pressure sensor S2R are attached to the turning hydraulic motor 2A. The left turning pressure sensor S2L detects the pressure of the hydraulic oil at the left port of the turning hydraulic motor 2A, and the right turning pressure sensor S2R detects the pressure of the hydraulic oil at the right port of the turning hydraulic motor 2A.

The control valve 174 is a spool valve for supplying the hydraulic oil discharged by the right main pump 14R to the bucket cylinder 9 and discharging the hydraulic oil in the bucket cylinder 9 to the hydraulic oil tank.

The control valve 175 is a spool valve that supplies the hydraulic oil discharged by the main pump 14 to the boom cylinder 7 and switches the flow of the hydraulic oil in order to discharge the hydraulic oil in the boom cylinder 7 to the hydraulic oil tank. Specifically, the control valve 175 includes a control valve 175L and a control valve 175R. The control valve 175L is a spool valve that switches the flow of hydraulic oil in order to supply the hydraulic oil discharged by the left main pump 14L to the oil chamber on the bottom side of the boom cylinder 7. The control valve 175R is a spool valve that supplies the hydraulic oil discharged by the right main pump 14R to the boom cylinder 7 and switches the flow of the hydraulic oil in order to discharge the hydraulic oil in the boom cylinder 7 to the hydraulic oil tank. ..

The control valve 176 is a spool valve that supplies the hydraulic oil discharged by the main pump 14 to the arm cylinder 8 and switches the flow of the hydraulic oil in order to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank. Specifically, the control valve 176 includes a control valve 176L and a control valve 176R. The control valve 176L is a spool valve that supplies the hydraulic oil discharged by the left main pump 14L to the arm cylinder 8 and switches the flow of the hydraulic oil in order to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank. .. The control valve 176R is a spool valve that supplies the hydraulic oil discharged by the right main pump 14R to the arm cylinder 8 and switches the flow of the hydraulic oil in order to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank. ..

The control valve 177 is configured to function as a unified bleed valve that uniformly controls the bleed flow rate of the hydraulic oil discharged from the main pump 14. Hereinafter, such unified control of the bleed flow rate will be referred to as "unified bleed control". In the present embodiment, the control valve 177 is composed of a spool valve and includes a control valve 177L and a control valve 177R. The control valve 177L uniformly controls the bleed flow rate of the hydraulic oil discharged by the left main pump 14L. The control valve 177R uniformly controls the bleed flow rate of the hydraulic oil discharged by the right main pump 14R. Specifically, the control valve 177L is configured to realize a unified bleed flow rate suitable for each movement amount of the control valves 171, 173, 175L, and 176L as spool valves. The bleed flow rate suitable for the movement amount of the control valve 171 is, for example, the PT port of the control valve configured so that the opening areas of the PT port, the PC port, and the CT port can be adjusted at the same time under the same conditions. It corresponds to the flow rate of hydraulic oil passing through. The same applies to the bleed flow rate for each of the control valves 173, 175 L, and 176 L. That is, the control valve 177L substantially has the opening areas of the PC ports and CT ports of the control valves 171, 173, 175L, and 176L, and the virtual control valves 171, 173, 175L, and 176L, respectively. It is configured so that the opening area of the PT port can be controlled separately.

Similarly, the control valve 177R is configured to achieve a uniform bleed flow rate suitable for the respective movement amounts of the control valves 172, 174, 175R, and 176R as spool valves. That is, the control valve 177R substantially has the opening areas of the PC ports and CT ports of the control valves 172, 174, 175R, and 176R, and the virtual areas of the control valves 172, 174, 175R, and 176R, respectively. It is configured so that the opening area of the PT port can be controlled separately.

The control valve 177 has, for example, a first valve position having a minimum opening area (opening 0%) and a second valve position having a maximum opening area (opening 100%). The control valve 177 can be steplessly positioned between the first valve position and the second valve position.

The regulator 13 controls the discharge amount of the main pump 14 by adjusting the tilt angle of the swash plate of the main pump 14. In the example shown in FIG. 3, the regulator 13 includes a left regulator 13L and a right regulator 13R. For example, the controller 30 adjusts the swash plate tilt angle of the left main pump 14L with the left regulator 13L in response to an increase in the discharge pressure of the left main pump 14L to reduce the discharge amount. This is to prevent the absorbed power (absorbed horsepower) of the left main pump 14L, which is represented by the product of the discharge pressure and the discharge amount, from exceeding the output power (output horsepower) of the engine 11. The same applies to the discharge rate of the right main pump.

The arm operating lever 26A is an example of the operating device 26, and is used for operating the arm 5. The arm operating lever 26A utilizes the hydraulic oil discharged from the pilot pump 15 to apply a pilot pressure corresponding to the lever operating amount to the pilot port of the control valve 176. Specifically, when the arm operating lever 26A is operated in the arm closing direction, the hydraulic oil is introduced into the right pilot port of the control valve 176L and the hydraulic oil is introduced into the left pilot port of the control valve 176R. .. Further, when the arm operating lever 26A is operated in the arm opening direction, the hydraulic oil is introduced into the left pilot port of the control valve 176L and the hydraulic oil is introduced into the right pilot port of the control valve 176R.

The boom operating lever 26B is an example of the operating device 26 and is used to operate the boom 4. The boom operating lever 26B utilizes the hydraulic oil discharged from the pilot pump 15 to apply a pilot pressure according to the lever operating amount to the pilot port of the control valve 175. Specifically, when the boom operating lever 26B is operated in the boom raising direction, the hydraulic oil is introduced into the right pilot port of the control valve 175L and the hydraulic oil is introduced into the left pilot port of the control valve 175R. .. Further, when the boom operating lever 26B is operated in the boom lowering direction, the hydraulic oil is introduced into the left pilot port of the control valve 175L and the hydraulic oil is introduced into the right pilot port of the control valve 175R.

The discharge pressure sensor 28 detects the discharge pressure of the main pump 14 and outputs the detected value to the controller 30. In the example shown in FIG. 3, the discharge pressure sensor 28 includes a left discharge pressure sensor 28L and a right discharge pressure sensor 28R. The left discharge pressure sensor 28L detects the discharge pressure of the left main pump 14L and outputs the detected value to the controller 30. The right discharge pressure sensor 28R detects the discharge pressure of the right main pump 14R and outputs the detected value to the controller 30.

The operating pressure sensor 29 detects the operation content of the operator with respect to the operating device 26 in the form of pressure, and outputs the detected value to the controller 30. In the example shown in FIG. 3, the operating pressure sensor 29 includes an arm operating pressure sensor 29A and a boom operating pressure sensor 29B. The arm operating pressure sensor 29A detects the operation content of the operator with respect to the arm operating lever 26A in the form of pressure, and outputs the detected value to the controller 30. The boom operation pressure sensor 29B detects the operation content of the operator with respect to the boom operation lever 26B in the form of pressure, and outputs the detected value to the controller 30. The operation contents are, for example, a lever operation direction and a lever operation amount (lever operation angle).

The traveling operation device (left traveling lever, right traveling lever, left traveling pedal, and right traveling pedal), the bucket operating lever, and the turning operating lever (none of which are shown) are the traveling of the lower traveling body 1 and the bucket 6 respectively. It is an operation device for operating the opening / closing of the upper swivel body 3 and the swivel of the upper swivel body 3. Similar to the arm operating lever 26A and the boom operating lever 26B, these operating devices utilize the hydraulic oil discharged by the pilot pump 15 and correspond to each of the hydraulic actuators with a pilot pressure according to the lever operating amount or the pedal operating amount. It acts on either the left or right pilot port of the control valve. The operator's operation content for each of these operating devices is detected in the form of pressure by the corresponding operating pressure sensor, similar to the arm operating pressure sensor 29A and the boom operating pressure sensor 29B, and the detected value is for the controller 30. It is output.

The controller 30 is configured to receive the output of the operating pressure sensor 29 and the like, output a control command to the regulator 13 as needed, and change the discharge amount of the main pump 14. Further, the controller 30 is configured to output a control command to the solenoid valve 31 as needed to change the opening area of the control valve 177.

In the example shown in FIG. 3, the solenoid valve 31 includes a left solenoid valve 31L and a right solenoid valve 31R. The left solenoid valve 31L can adjust the pilot pressure so that the control valve 177L can be stopped at an arbitrary position between the first valve position and the second valve position. The right solenoid valve 31R can adjust the pilot pressure so that the control valve 177R can be stopped at an arbitrary position between the first valve position and the second valve position.

Next, the negative control control adopted in the hydraulic system shown in FIG. 3 will be described. In the oil passage 42, a throttle 18 is arranged between the most downstream control valve 177 and the hydraulic oil tank. The flow of hydraulic oil through the control valve 177 to the hydraulic oil tank is restricted by the throttle 18. Then, the throttle 18 generates a control pressure for controlling the regulator 13, that is, a control pressure for controlling the discharge amount of the main pump 14. The control pressure sensor 19 is a sensor for detecting the control pressure, and outputs the detected value to the controller 30.

In the present embodiment, the throttle 18 is a fixed throttle whose opening area does not change, and in the left oil passage 42L, in the left throttle 18L arranged between the control valve 177L and the hydraulic oil tank, and in the right oil passage 42R. Includes a right throttle 18R arranged between the control valve 177R and the hydraulic oil tank. The control pressure sensor 19 includes a left control pressure sensor 19L that detects the control pressure generated by the left throttle 18L to control the left regulator 13L, and a control pressure generated by the right throttle 18R to control the right regulator 13R. Includes a right control pressure sensor 19R, which detects

The controller 30 controls the discharge amount of the main pump 14 by adjusting the swash plate tilt angle of the main pump 14 according to the control pressure. Hereinafter, the relationship between the control pressure and the discharge amount of the main pump 14 will be referred to as “negative control characteristics”. The negative control characteristic may be stored in a ROM or the like as a reference table, or may be expressed by a predetermined calculation formula. The controller 30 refers to, for example, a reference table representing a predetermined negative control characteristic, and increases the discharge amount of the main pump 14 as the control pressure is larger, and increases the discharge amount of the main pump 14 as the control pressure is smaller.

Specifically, as shown in FIG. 3, in the standby state in which none of the hydraulic actuators is operated, the hydraulic oil discharged by the left main pump 14L reaches the left throttle 18L through the control valve 177L. Then, the increase in the flow of hydraulic oil passing through the control valve 177L increases the control pressure generated upstream of the left throttle 18L. As a result, the controller 30 reduces the discharge amount of the left main pump 14L to a predetermined allowable minimum discharge amount, and suppresses the pressure loss (pumping loss) when the discharged hydraulic oil passes through the left oil passage 42L. This predetermined allowable minimum discharge amount in the standby state is an example of the bleed flow rate, and is hereinafter referred to as "standby flow rate". The controller 30 also controls the discharge amount of the right main pump 14R in the same manner.

On the other hand, when any of the hydraulic actuators is operated, the hydraulic oil discharged from the left main pump 14L flows into the operation target hydraulic actuator through the control valve corresponding to the operation target hydraulic actuator. Therefore, the bleed flow rate through the control valve 177L to the left throttle 18L decreases, and the control pressure generated upstream of the left throttle 18L decreases. As a result, the controller 30 increases the discharge amount of the left main pump 14L, supplies sufficient hydraulic oil to the operation target hydraulic actuator, and ensures the drive of the operation target hydraulic actuator. The controller 30 also controls the discharge amount of the right main pump 14R in the same manner. In the following, the flow rate of hydraulic oil flowing into the hydraulic actuator will be referred to as "actuator flow rate". In this case, the flow rate of the hydraulic oil discharged by the left main pump 14L corresponds to the sum of the actuator flow rate for the left oil passage 42L and the bleed flow rate for the left oil passage 42L. The same applies to the flow rate of the hydraulic oil discharged by the right main pump 14R.

With the above configuration, the hydraulic system shown in FIG. 3 can reliably supply the necessary and sufficient hydraulic oil from the main pump 14 to the hydraulic actuator to be operated when the hydraulic actuator is operated. Further, in the standby state, the hydraulic system shown in FIG. 3 can suppress wasteful consumption of hydraulic energy. This is because the bleed flow rate can be reduced to the standby flow rate.

The relief valve 50 is configured to discharge the hydraulic oil to the hydraulic oil tank when the pressure of the hydraulic oil in the oil passage 42 exceeds a predetermined relief pressure. This is because an excessive increase in hydraulic oil pressure in the oil passage 42 may result in damage to the hydraulic equipment or structures constituting the hydraulic system. In the example shown in FIG. 3, the relief valve 50 is arranged in the oil passage 43 connecting the oil passage 42 and the hydraulic oil tank. A check valve 51 is arranged in the oil passage 43.

The check valve 51 is configured to stop the flow of hydraulic oil from the hydraulic oil tank to the oil passage 42. In the example shown in FIG. 3, the check valve 51 has a left check valve 51L that stops the flow of hydraulic oil from the hydraulic oil tank to the left oil passage 42L and a check valve 51 that stops the flow of hydraulic oil from the hydraulic oil tank to the right oil passage 42R. Includes right check valve 51R.

The oil passage 43 includes a central oil passage 43C, a left oil passage 43L, and a right oil passage 43R. The left oil passage 43L is an oil passage connecting the left oil passage 42L and the central oil passage 43C, and the right oil passage 43R is an oil passage connecting the right oil passage 42R and the central oil passage 43C.

In the example shown in FIG. 3, the relief valve 50 is arranged in the central oil passage 43C, the left check valve 51L is arranged in the left oil passage 43L, and the right check valve 51R is arranged in the right oil passage 43R.

As described above, the flood control system shown in FIG. 3 is configured so that one relief valve 50 can discharge hydraulic oil in each of the left oil passage 42L and the right oil passage 42R to the hydraulic oil tank. However, the hydraulic system shown in FIG. 3 has a left relief valve for discharging the hydraulic oil in the left oil passage 42L to the hydraulic oil tank and a right relief valve for discharging the hydraulic oil in the right oil passage 42R to the hydraulic oil tank. And may be provided separately. In this case, the left relief valve is arranged in the oil passage connecting the left oil passage 42L and the hydraulic oil tank, and the right relief valve is arranged in the oil passage connecting the right oil passage 42R and the hydraulic oil tank.

The hydraulic system shown in FIG. 3 is basically configured to change the opening area of the control valve 177 according to the operating amount of the operating device 26 regardless of the load applied to the hydraulic actuator. For example, the hydraulic system shown in FIG. 3 has two or more hydraulic actuators related to two or more of the left traveling hydraulic motor 1A, the turning hydraulic motor 2A, the boom cylinder 7, and the arm cylinder 8 with respect to the left oil passage 42L. When the operating devices 26 are operated at the same time, the opening area of the control valve 177L is changed according to the total operating amount of all the operating devices 26 being operated. Typically, the hydraulic system shown in FIG. 3 is configured so that the larger the total amount of operation, the smaller the opening area of the control valve 177L. Similarly, the hydraulic system shown in FIG. 3 has two or more operations relating to two or more hydraulic actuators of the right traveling hydraulic motor 1B, the bucket cylinder 9, the boom cylinder 7, and the arm cylinder 8 with respect to the right oil passage 42R. When the devices 26 are operated at the same time, the opening area of the control valve 177R is changed according to the total operation amount of all the operating devices 26 being operated. Typically, the hydraulic system shown in FIG. 3 is configured so that the larger the total amount of operation, the smaller the opening area of the control valve 177L.

However, for example, in a configuration in which the opening area of the control valve 177L is determined based only on the lever operating amount of the arm operating lever 26A when closing the arm 5, if the lever operating amount of the arm operating lever 26A is the same, the arm cylinder The actuator flow rate, which is the flow rate of the hydraulic oil flowing into the bottom side oil chamber of No. 8, decreases as the arm bottom pressure increases. This is because the hydraulic oil discharged by the left main pump 14L flows through an oil passage in which the pressure loss is relatively small, that is, an oil passage in which the control valve 177L is arranged. This means that if the lever operating amount of the arm operating lever 26A is the same, the higher the arm bottom pressure, the larger the bleed flow rate and the larger the flow rate of the hydraulic oil wastefully discharged to the hydraulic oil tank. ..

Therefore, in the hydraulic system shown in FIG. 3, when the load applied to the hydraulic actuator exceeds a predetermined value, the opening area of the control valve 177 changes regardless of the operation amount of the operating device 26 related to the hydraulic actuator. It is configured in. For example, when the load applied to the hydraulic actuator exceeds a predetermined value, the controller 30 adjusts the opening area of the control valve 177 according to the load applied to the hydraulic actuator regardless of the operating amount of the operating device 26 related to the hydraulic actuator. It is configured to do.

Further, in FIG. 3, the control valves 171, 173, 175L, and 176L that control the flow of hydraulic oil from the left main pump 14L to the hydraulic actuator are parallel to each other between the left main pump 14L and the hydraulic oil tank. It is connected to the. However, each of the control valves 171, 173, 175L, and 176L may be connected in series between the left main pump 14L and the hydraulic oil tank. In this case, regardless of which valve position the spool constituting each control valve is switched to, the left oil passage 42L is not interrupted by the spool, and hydraulic oil is applied to the adjacent control valve arranged on the downstream side. Can be supplied.

Similarly, the control valves 172, 174, 175R, and 176R that control the flow of hydraulic oil from the right main pump 14R to the hydraulic actuator are respectively connected in parallel between the right main pump 14R and the hydraulic oil tank. ing. However, each of the control valves 172, 174, 175R, and 176R may be connected in series between the right main pump 14R and the hydraulic oil tank. In this case, regardless of which valve position the spool constituting each control valve is switched to, the right oil passage 42R is not interrupted by the spool, and hydraulic oil is applied to the adjacent control valve arranged on the downstream side. Can be supplied.

Here, with reference to FIG. 4, a process in which the controller 30 adjusts the opening area of the control valve 177 (hereinafter, referred to as “adjustment process”) will be described. FIG. 4 shows a flowchart of an example of the adjustment process. Apart from the unified bleed control, the controller 30 repeatedly executes this adjustment process at a predetermined control cycle.

First, the controller 30 detects the load of the hydraulic actuator (step ST1). For example, the controller 30 detects the magnitude of the load applied to the arm cylinder 8 based on the output of the arm bottom pressure sensor S8B when the arm closing operation is being performed.

After that, the controller 30 determines whether or not the load exceeds a predetermined value (step ST2). For example, the controller 30 determines whether or not the arm bottom pressure detected by the arm bottom pressure sensor S8B exceeds a predetermined pressure.

When it is determined that the load does not exceed the predetermined value (NO in step ST2), the controller 30 ends the current adjustment process without adjusting the opening area of the control valve 177 as the bleed valve.

On the other hand, when it is determined that the load exceeds a predetermined value (YES in step ST2), the controller 30 reduces the opening area of the control valve 177 as a bleed valve (step ST3). For example, when the controller 30 determines that the arm bottom pressure exceeds a predetermined pressure, the controller 30 reduces the opening area of the control valve 177. Specifically, the controller 30 reduces the opening areas of the control valve 177L and the control valve 177R, respectively.

If the lever operating amount of the arm operating lever 26A does not change and the arm bottom pressure increases, the hydraulic oil discharged by the main pump 14 becomes difficult to flow into the bottom side oil chamber of the arm cylinder 8, and the control valve 177 It becomes easier to flow toward. At this time, if the opening area of the control valve 177 is not reduced, the bleed flow rate, which is the flow rate of the hydraulic oil passing through the control valve 177, increases, and the flow rate of the hydraulic oil wastefully discharged to the hydraulic oil tank increases. Will end up. Further, as the bleed flow rate increases, the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the bottom oil chamber of the arm cylinder 8, decreases or disappears, and the movement of the arm 5 slows down or stops.

At this time, the controller 30 can suppress or prevent an increase in the bleed flow rate by reducing the opening area of the control valve 177 even when the lever operating amount of the arm operating lever 26A does not change, and the hydraulic oil tank can be used. It is possible to suppress or prevent an increase in the flow rate of the hydraulic oil that is wasted. Further, the controller 30 can suppress or prevent a decrease in the actuator flow rate by suppressing or prevent an increase in the bleed flow rate, and can prevent the movement of the arm 5 from slowing down or stopping.

In the present embodiment, the controller 30 disables the negative control control when reducing the opening area of the control valve 177. That is, the controller 30 is configured to maintain the discharge amount of the main pump 14 at that time. When the opening area of the control valve 177 is reduced while the negative control control is enabled, the discharge amount of the main pump 14 increases as the bleed flow rate decreases, and as a result, the actuator flow rate becomes the load applied to the hydraulic actuator. This is because the flow rate of the actuator before exceeding the predetermined value becomes significantly larger than the flow rate of the actuator.

Further, in the present embodiment, the controller 30 changes the degree of decrease in the opening area of the control valve 177 according to the magnitude of the load applied to the hydraulic actuator. Specifically, the controller 30 is configured so that the degree of reduction increases as the load increases, that is, the opening area decreases as the load increases. However, the degree of decrease in the opening area of the control valve 177 may be constant regardless of the magnitude of the load.

Further, in the present embodiment, the controller 30 reduces the opening area of the control valve 177 when it is determined that the load exceeds the predetermined value, for example, when the arm bottom pressure is determined to exceed the predetermined pressure. However, the controller 30 may reduce the opening area of the control valve 177 when it is determined that the fluctuation range of the arm bottom pressure in the state where the lever operating amount of the arm operating lever 26A does not change exceeds a predetermined width.

In the example shown in FIG. 4, the controller 30 is configured to reduce the opening area of the control valve 177 when it is determined that the load applied to the hydraulic actuator exceeds a predetermined value. However, when the controller 30 determines that the load applied to the hydraulic actuator exceeds a predetermined value and then determines that the operating device 26 is further operated in the direction in which the load is further increased, the opening area of the control valve 177 is determined. May be configured to reduce. For example, the controller 30 determines that the load applied to the arm cylinder 8 exceeds a predetermined value when the arm closing operation for excavation is being performed, and then operates the arm operating lever 26A in the arm closing direction. When it is determined that the amount has increased to a predetermined amount or more, the opening area of the control valve 177 may be reduced. After confirming the operator's intention to push away the excavated object such as earth and sand that causes an increase in load and continue the arm closing operation, the excavation force by the arm cylinder 8 is applied by reflecting the operator's intention. This is to increase. Conversely, this is to prevent the excavation force of the arm cylinder 8 from being increased even though the operator does not have such an intention. However, when the excavator 100 is operated by remote control, or when the excavator 100 is autonomously controlled, the determination as to whether or not the operating device 26 has been further operated may be omitted.

Next, the effect of the adjustment process will be described with reference to FIG. FIG. 5 is a left side view of the excavation attachment that executes the slope forming work. The excavator 100 performs a combined operation including a boom raising operation and an arm closing operation. FIG. 5 includes FIGS. 5 (A) to 5 (C). FIG. 5A shows the state of the excavator 100 before the load applied to the arm cylinder 8 exceeds a predetermined value. FIG. 5B shows a case where the controller 30 continues the combined operation without reducing the opening area of the control valve 177 when the load applied to the arm cylinder 8 exceeds a predetermined value in the excavator 100 in which the adjustment process is not executed. The state of the excavator 100 after that is shown. FIG. 5C shows a case where the controller 30 reduces the opening area of the control valve 177 to continue the combined operation when the load applied to the arm cylinder 8 exceeds a predetermined value in the excavator 100 in which the adjustment process is executed. The state of the excavator 100 after that is shown. The dotted lines in each of FIGS. 5 (A) to 5 (C) represent the positions of the target surface TS, which is the slope when the work is completed. The bucket 6A shown by the broken line in each of FIGS. 5 (B) and 5 (C) represents the position of the bucket 6 shown in FIG. 5 (A).

Specifically, FIG. 5 (A) shows that the toe of the bucket 6 is in contact with the hard raised portion BP on the slope during the slope forming work, and the arm operating lever 26A is operated in the closing direction. However, it shows a state in which the closing operation of the arm 5 is slowed down. At this time, in the excavator 100 in which the adjustment process is not executed, the actuator flow rate decreases and the bleed flow rate only increases while maintaining the lever operation amount of the arm operation lever 26A, so that the operator closes the arm 5. Can't. Therefore, the operator typically increases the lever operating amount.

However, the operator knows how much the lever operating amount of the arm operating lever 26A should be increased to excavate the raised portion BP, that is, to restart the arm closing operation at a desired closing speed. Can't. Therefore, the operator may excessively operate the arm operating lever 26A in the closing direction.

When the arm operating lever 26A is excessively operated in the closing direction, the opening areas of the PC port and the CT port of the control valve 176 increase sharply, while the opening area of the control valve 177 sharply decreases due to the unified bleed control. Therefore, the discharge amount of the main pump 14 rapidly increases due to the negative control control. When the discharge pressure of the main pump 14 exceeds the arm bottom pressure, the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the bottom side oil chamber of the arm cylinder 8, rapidly increases, the arm cylinder 8 rapidly expands, and the arm 5 Is closed abruptly. As a result, as shown in FIG. 5B, the toes of the bucket 6 exceed the target surface TS and enter the slope.

Therefore, the controller 30 flows into the oil chamber on the bottom side of the arm cylinder 8 by executing the adjustment process, that is, by reducing the opening area of the control valve 177 when the arm bottom pressure exceeds a predetermined pressure. It prevents the hydraulic oil to be discharged from being discharged to the hydraulic oil tank through the control valve 177.

When the adjustment process is executed, the operator can excavate the raised portion BP and close the arm 5 even while maintaining the lever operating amount of the arm operating lever 26A. Even if the actuator flow rate temporarily decreases, the opening area of the control valve 177 decreases thereafter, so that the temporarily increased bleed flow rate decreases and the temporarily decreased actuator flow rate increases. Is. Further, since the opening area of the control valve 177 is reduced, the pressure of the hydraulic oil flowing into the bottom side oil chamber of the arm cylinder 8 is higher than that before the adjustment process is executed.

In this way, when the adjustment process is executed, the operator can excavate the raised portion BP and close the arm 5 even while maintaining the lever operating amount of the arm operating lever 26A. , It is not necessary to increase the lever operation amount of the arm operation lever 26A. Therefore, the operator does not suddenly move the toes of the bucket 6. As a result, as shown in FIG. 5C, the toe of the bucket 6 does not exceed the target surface TS and enters the slope, and the toe of the bucket 6 becomes the target surface TS by a combined operation including a boom raising operation and an arm closing operation. Move along.

Next, with reference to FIG. 6, as the arm bottom pressure when the slope forming work as shown in FIG. 5 is performed, the opening area of the control valve 177L as a bleed valve, and the flow rate of hydraulic oil passing through the control valve 177L. The bleed flow rate of the above and the temporal transition of the actuator flow rate as the flow rate of the hydraulic oil passing through the PC port of the control valve 176L will be described. FIG. 6 shows an example of the temporal transition of the arm bottom pressure, the opening area of the control valve 177L, the bleed flow rate, and the actuator flow rate when the slope forming operation as shown in FIG. 5 is performed. The transition represented by the solid line shown in FIG. 6 indicates the transition when the adjustment process is executed, and the transition represented by the dotted line shown in FIG. 6 indicates the transition when the adjustment process is not executed. In the following description, the opening area of the control valve 177R, the bleed flow rate as the flow rate of the hydraulic oil passing through the control valve 177R among the hydraulic oil discharged by the right main pump 14R, and the right main pump 14R discharge. The same applies to the actuator flow rate as the flow rate of the hydraulic oil passing through the control valve 176R of the hydraulic oil.

When the toe of the bucket 6 hits the raised portion BP (see FIG. 5), the arm bottom pressure gradually increases as the arm closing operation progresses, as shown in FIG. 6 (A), and at time t1, the predetermined pressure Reach Pth.

When it is determined that the arm bottom pressure exceeds the predetermined pressure Pth, the controller 30 outputs a control command to the control valve 177L and reduces the opening area of the control valve 177L. As a result, as shown in FIG. 6 (B), the opening area of the control valve 177L starts to decrease at time t1, and thereafter, it is controlled to decrease as the arm bottom pressure increases. The flow rate of the hydraulic oil flowing into the bottom oil chamber of the arm cylinder 8 via the PC port of the control valve 176L so that the bleed flow rate, which is the flow rate of the hydraulic oil passing through the control valve 177L, becomes a desired flow rate. This is to ensure that the actuator flow rate is a desired flow rate.

Specifically, the opening area of the control valve 177L is desired so that the bleed flow rate is the desired flow rate Qbt as shown in FIG. 6 (C) and the actuator flow rate is desired as shown in FIG. 6 (D). It is controlled so that the flow rate is Qat.

In the present embodiment, the actuator flow rate is calculated as the flow rate of hydraulic oil passing through the PC port of the control valve 176L based on the differential pressure between the discharge pressure of the left main pump 14L and the arm bottom pressure. The discharge pressure of the left main pump 14L is detected based on the output of the left discharge pressure sensor 28L, and the arm bottom pressure is detected based on the output of the arm bottom pressure sensor S8B. The bleed flow rate is calculated as the flow rate of hydraulic oil passing through the control valve 177L based on the differential pressure between the discharge pressure of the left main pump 14L and the control pressure detected by the left control pressure sensor 19L. The discharge amount of the left main pump 14L is calculated as the sum of the actuator flow rate and the bleed flow rate. The discharge amount of the left main pump 14L is calculated based on the swash plate tilt angle corresponding to the control command for the left regulator 13L. The discharge amount of the left main pump 14L may be detected by the swash plate tilt angle sensor. The bleed flow rate may be calculated as a value obtained by subtracting the actuator flow rate from the discharge amount of the left main pump 14L. The actuator flow rate may be calculated as a value obtained by subtracting the bleed flow rate from the discharge amount of the left main pump 14L.

The relationship between the opening area of the control valve 177L, the discharge pressure of the left main pump 14L, and the arm bottom pressure may be stored in advance in a ROM or the like as a reference table. In this case, the controller 30 can determine the opening area of the control valve 177L based on the discharge pressure of the left main pump 14L and the arm bottom pressure by referring to this reference table. The reference table is typically set for each excavator model.

When the adjustment process is executed as described above, the opening area of the control valve 177L is obtained when the adjustment process is not executed (see the dotted line in FIG. 6 (B)) as shown by the solid line in FIG. 6 (B). It is controlled to be smaller than that. When the adjustment process is not executed, the opening area of the control valve 177L is the opening area corresponding to the lever operating amount if the lever operating amount of the arm operating lever 26A is constant, as shown by the dotted line in FIG. 6 (B). This is because it is maintained at.

As shown by the solid line in FIG. 6C, the bleed flow rate is controlled to be smaller than that in the case where the adjustment process is not executed (see the dotted line in FIG. 6C). This is because when the adjustment process is not executed, the bleed flow rate increases by the amount that the actuator flow rate decreases, as shown by the dotted line in FIG. 6C.

As shown by the solid line in FIG. 6 (D), the actuator flow rate is controlled to be larger than that in the case where the adjustment process is not executed (see the dotted line in FIG. 6 (D)). When the adjustment process is not executed, the actuator flow rate is as shown by the dotted line in FIG. 6 (D), and if the lever operating amount of the arm operating lever 26A is constant, the arm bottom is shown by the dotted line in FIG. 6 (A). This is because it becomes difficult to flow into the bottom side oil chamber of the arm cylinder 8 as the pressure increases, that is, it decreases as the arm bottom pressure increases.

The rate of increase in the arm bottom pressure increases after time t1 as compared with the case where the adjustment process is not executed (see the dotted line in FIG. 6 (A)), as shown by the solid line in FIG. 6 (A). .. In the example shown in FIG. 6, the controller 30 suppresses the increase in the bleed flow rate so that the bleed flow rate is maintained at the desired flow rate Qbt, and the flow rate of the hydraulic oil flowing into the bottom oil chamber of the arm cylinder 8 is used. This is because the decrease in the flow rate of a certain actuator is suppressed.

As described above, the excavator 100 is configured to adjust the opening area of the control valve 177 according to the load applied to the hydraulic actuator. With this configuration, the excavator 100 can smooth the movement of the hydraulic actuator when the load applied to the hydraulic actuator changes during the operation of the hydraulic actuator. This is because the change in the flow rate of the hydraulic oil flowing into the hydraulic actuator can be suppressed without the operator changing the lever operation amount.

In the above-described embodiment, the controller 30 is configured so that when it is determined that the load exceeds a predetermined value, the negative control control is invalidated so that the discharge amount of the main pump 14 does not change before and after the determination. Has been done. This is to prevent the operating speed of the hydraulic actuator from changing before and after the determination.

For example, the controller 30 is configured so that when it is determined that the arm bottom pressure exceeds a predetermined pressure during the slope forming work, the discharge amount of the main pump 14 is not changed before and after the determination. ing. This is to prevent the extension speed of the arm cylinder 8 from changing before and after the determination.

However, the controller 30 may be configured to increase or decrease the discharge amount of the main pump 14 after determining that the load exceeds a predetermined value. This is to prevent the extension speed of the arm cylinder 8 from changing before and after the determination. Specifically, simply not changing the discharge amount of the main pump 14 before and after the determination cannot prevent the change in the extension speed of the arm cylinder 8 before and after the determination, such as when an external factor is large. This is because situations can occur. For example, if the decrease in the actuator flow rate cannot be compensated for by simply reducing the opening area of the control valve 177, the controller 30 may increase the discharge amount of the main pump 14.

Alternatively, the controller 30 may be configured to reduce the discharge amount of the main pump 14 by a predetermined amount after determining that the load exceeds a predetermined value. With this configuration, after the controller 30 determines that the load has exceeded a predetermined value, the operation speed of the hydraulic actuator is slowed down by a predetermined amount while maintaining the smooth operation of the hydraulic actuator. , The operator can be made aware that the load has increased.

Further, in the above example, the controller 30 is configured to reduce the opening area of the control valve 177 as a bleed valve when it is determined that the load applied to the hydraulic actuator exceeds a predetermined value. This is to allow the hydraulic actuator to operate continuously and smoothly while preventing the hydraulic actuator from becoming excessively slow even when the load applied to the hydraulic actuator increases. However, the controller 30 may be configured to increase the opening area of the control valve 177 as a bleed valve when it is determined that the load applied to the hydraulic actuator is less than a predetermined value. This is to allow the hydraulic actuator to operate continuously and smoothly while preventing the hydraulic actuator from moving excessively fast even when the load applied to the hydraulic actuator is reduced.

Further, preferably, when the controller 30 determines that the load applied to the hydraulic actuator exceeds the predetermined value, reduces the opening area of the control valve 177, and then determines that the load falls below the predetermined value. The adjustment of the opening area of the control valve 177 by the adjustment process is stopped. That is, in the present embodiment, the controller 30 is configured to restart the adjustment of the opening area of the control valve 177 by the unified bleed control. However, in order to avoid a sudden change in the bleed flow rate when the unified bleed control is enabled, the controller 30 is a control valve determined by the unified bleed control from the opening area of the control valve 177 adjusted (determined) by the adjustment process. The rate of change of the opening area when changing to the opening area of 177 may be limited. Further, the controller 30 is configured to enable the negative control control that has been disabled when the adjustment of the opening area of the control valve 177 by the adjustment process is stopped. However, in order to avoid a sudden change in the discharge amount of the main pump 14 when the negative control control is enabled, the controller 30 determines the main pump 14 by the negative control control from the discharge amount of the main pump 14 at the time of the adjustment process. The rate of change of the swash plate tilt angle when changing to the discharge amount of

Next, another configuration example of the excavator 100 will be described with reference to FIG. 7. FIG. 7 is a side view of the excavator 100 and corresponds to FIG. The excavator 100 shown in FIG. 7 is different from the excavator 100 shown in FIG. 1 in that it includes a boom angle sensor S1, an arm angle sensor S2, and a bucket angle sensor S3. Therefore, in the following, the explanation of the common part will be omitted and the difference part will be described in detail.

The boom angle sensor S1 is configured to detect the rotation angle of the boom 4. In the present embodiment, the boom angle sensor S1 is an acceleration sensor, and can detect the rotation angle of the boom 4 with respect to the upper swing body 3 (hereinafter, referred to as “boom angle”). The boom angle becomes zero degrees when the boom 4 is lowered to the maximum, and increases as the boom 4 is raised.

The arm angle sensor S2 is configured to detect the rotation angle of the arm 5. In the present embodiment, the arm angle sensor S2 is an acceleration sensor and can detect the rotation angle of the arm 5 with respect to the boom 4 (hereinafter, referred to as “arm angle”). The arm angle becomes zero degrees when the arm 5 is most closed, and increases as the arm 5 is opened.

The bucket angle sensor S3 is configured to detect the rotation angle of the bucket 6. In the present embodiment, the bucket angle sensor S3 is an acceleration sensor and can detect the rotation angle of the bucket 6 with respect to the arm 5 (hereinafter, referred to as “bucket angle”). The bucket angle becomes zero degrees when the bucket 6 is closed most, and increases as the bucket 6 is opened.

The boom angle sensor S1, arm angle sensor S2, and bucket angle sensor S3 are a potentiometer using a variable resistor, a stroke sensor that detects the stroke amount of the corresponding hydraulic cylinder, and a rotary that detects the rotation angle around the connecting pin. It may be an encoder, a gyro sensor, or a combination of an acceleration sensor and a gyro sensor.

Next, with reference to FIG. 8, a configuration example of the hydraulic system mounted on the excavator 100 shown in FIG. 7 will be described. FIG. 8 is a schematic view showing a configuration example of the hydraulic system mounted on the excavator 100 shown in FIG. 7, and corresponds to FIG. FIG. 8 shows the mechanical power transmission line, the hydraulic oil line, the pilot line, and the electric control line as double-dashed lines, solid lines, dotted lines, and alternate-dotted lines, respectively, as in FIG.

The hydraulic system shown in FIG. 8 circulates hydraulic oil from the main pump 14 driven by the engine 11 to the hydraulic oil tank via the oil passage 42 (including the center bypass oil passage 40 and the bleed oil passage 41). It differs from the hydraulic system shown in FIG. 3 in that it includes a control valve 170 as a traveling straight-ahead valve. Therefore, in the following, the explanation of the common part will be omitted and the difference part will be described in detail.

The center bypass oil passage 40 includes a left center bypass oil passage 40L and a right center bypass oil passage 40R. The left main pump 14L circulates hydraulic oil to the hydraulic oil tank via the left center bypass oil passage 40L passing through the control valves 171, 173, 175L, and 176L. The right main pump 14R circulates hydraulic oil to the hydraulic oil tank via the right center bypass oil passage 40R passing through the control valves 170, 172, 174, 175R, and 176R.

The bleed oil passage 41 includes a left bleed oil passage 41L and a right bleed oil passage 41R. The left bleed oil passage 41L is an oil passage connecting the left center bypass oil passage 40L and the hydraulic oil tank, and is connected to a partial BF1 between the control valve 171 and the control valve 173 in the left center bypass oil passage 40L. .. The right bleed oil passage 41R is an oil passage connecting the right center bypass oil passage 40R and the hydraulic oil tank, and is connected to a partial BF2 between the control valve 172 and the control valve 174 in the right center bypass oil passage 40R. ..

The control valve 170 is a spool valve provided on the upstream side of the control valve 172 in the right center bypass oil passage 40R and functions as a traveling straight valve. Then, the control valve 170 is in the first state of supplying the hydraulic oil discharged by the left main pump 14L to the left traveling hydraulic motor 1A and supplying the hydraulic oil discharged by the right main pump 14R to the right traveling hydraulic motor 1B. , The second state in which the hydraulic oil discharged by the left main pump 14L is supplied to both the left traveling hydraulic motor 1A and the right traveling hydraulic motor 1B can be switched. FIG. 8 shows how the first state is realized by the control valve 170.

Specifically, the control valve 170 bypasses the hydraulic oil discharged by the right main pump 14R in order to realize the second state when the traveling operation and the operation of the other hydraulic actuator are performed at the same time. It is supplied to the downstream side of the control valve 171 via the route and flows into the left center bypass oil passage 40L. Further, the control valve 170 supplies the hydraulic oil discharged by the left main pump 14L to the upstream side of the control valve 172 via the bypass oil passage BP1 and flows into the right center bypass oil passage 40R. As a result, only the hydraulic oil discharged by the left main pump 14L is supplied to both the left traveling hydraulic motor 1A and the right traveling hydraulic motor 1B, so that the straightness of the lower traveling body 1 is improved.

On the other hand, in order to realize the first state, the control valve 170 allows the hydraulic oil discharged by the right main pump 14R to pass as it is to the downstream side, and the left main pump 14L discharges the hydraulic oil when only the traveling operation is performed. The hydraulic oil is supplied to the downstream side of the control valve 171 via the bypass oil passage BP1 and flows into the left center bypass oil passage 40L. As a result, the hydraulic oil discharged by the left main pump 14L is supplied to the left traveling hydraulic motor 1A, and the hydraulic oil discharged by the right main pump 14R is supplied to the right traveling hydraulic motor 1B. The running performance of 1 is improved.

The control valve 171 is arranged upstream of the partial BF1 in the left center bypass oil passage 40L. The control valve 171 controls the direction and flow rate of the hydraulic oil flowing in and out of the left traveling hydraulic motor 1A according to the pilot pressure input from the left traveling lever to either the left or right pilot port.

In the example shown in FIG. 8, the control valve 171 has a PC port for allowing hydraulic oil to flow from the left main pump 14L to the left traveling hydraulic motor 1A, and hydraulic oil flowing from the left traveling hydraulic motor 1A to the hydraulic oil tank. It is a spool valve including a PT port for allowing hydraulic oil to flow from the left main pump 14L to the hydraulic oil tank.

The control valve 171 is configured to limit or shut off the opening area of the PT port according to the spool position. Specifically, the control valve 171 limits or shuts off the opening area of the PT port when the spool is not in the neutral position, that is, when hydraulic oil is flowing into the left traveling hydraulic motor 1A. In this case, hydraulic oil is supplied to the downstream side of the control valve 171 via the bypass oil passage BP2.

The control valve 172 is located upstream of the partial BF2 in the right center bypass oil passage 40R. The control valve 172 controls the direction and flow rate of the hydraulic oil flowing in and out of the right traveling hydraulic motor 1B according to the pilot pressure input from the right traveling lever to either the left or right pilot port.

In the example shown in FIG. 8, the control valve 172 has a PC port for allowing hydraulic oil to flow from the main pump 14 to the right-running hydraulic motor 1B, and hydraulic oil for flowing from the right-running hydraulic motor 1B to the hydraulic oil tank. It is a spool valve including a PT port for making the hydraulic oil flow from the main pump 14 to the hydraulic oil tank.

The control valve 172 is configured to limit or shut off the opening area of the PT port according to the spool position. Specifically, the control valve 172 limits or shuts off the opening area of the PT port when the spool is not in the neutral position, that is, when hydraulic oil is flowing into the right traveling hydraulic motor 1B. In this case, hydraulic oil is supplied to the downstream side of the control valve 172 via the bypass oil passage BP3.

Control valves 173, 175L, and 176L are located downstream of partial BF1 in the left center bypass oil passage 40L. The control valve 173 controls the direction and flow rate of the hydraulic oil flowing in and out of the turning hydraulic motor 2A according to the pilot pressure input from the turning operation lever to either the left or right pilot port. The control valve 175L controls the direction and flow rate of the hydraulic oil flowing in and out of the boom cylinder 7 according to the pilot pressure input from the boom operating lever to either the left or right pilot port. The control valve 176L controls the direction and flow rate of the hydraulic oil flowing in and out of the arm cylinder 8 according to the pilot pressure input from the arm operating lever to either the left or right pilot port.

In the example shown in FIG. 8, the control valve 173 has a PC port for allowing hydraulic oil to flow from the main pump 14 to the swivel hydraulic motor 2A, and a control valve 173 for allowing hydraulic oil to flow from the swivel hydraulic motor 2A to the hydraulic oil tank. It is a spool valve including a PT port and a PT port for allowing hydraulic oil to flow from the upstream side to the downstream side of the control valve 173.

The control valve 175L has a PC port for allowing hydraulic oil to flow from the main pump 14 to the boom cylinder 7 or allowing hydraulic oil to flow from the boom cylinder 7 to the left center bypass oil passage 40L, and an upstream of the control valve 173. It is a spool valve including a PT port for allowing hydraulic oil to flow from the side to the downstream side.

The control valve 176L is a spool valve including a PC port for allowing hydraulic oil to flow from the main pump 14 to the arm cylinder 8 and a CT port for allowing hydraulic oil to flow from the arm cylinder 8 to the hydraulic oil tank.

Control valves 174, 175R, and 176R are located downstream of partial BF2 in the right center bypass oil passage 40R. The control valve 174 controls the direction and flow rate of the hydraulic oil flowing in and out of the bucket cylinder 9 according to the pilot pressure input from the bucket operating lever to either the left or right pilot port. The control valve 175R controls the direction and flow rate of the hydraulic oil flowing in and out of the boom cylinder 7 according to the pilot pressure input from the boom operating lever to either the left or right pilot port. The control valve 176R controls the direction and flow rate of the hydraulic oil flowing in and out of the arm cylinder 8 according to the pilot pressure input from the arm operating lever to either the left or right pilot port.

In the example shown in FIG. 8, the control valve 174 has a PC port for allowing hydraulic oil to flow from the right main pump 14R to the bucket cylinder 9 and a PT port for allowing hydraulic oil to flow from the bucket cylinder 9 to the hydraulic oil tank. , A spool valve including a PT port for allowing hydraulic oil to flow from the upstream side to the downstream side of the control valve 174.

The control valve 175R has a PC port for allowing hydraulic oil to flow from the right main pump 14R to the boom cylinder 7, a PT port for allowing hydraulic oil to flow from the boom cylinder 7 to the hydraulic oil tank, and an upstream side of the control valve 175R. It is a spool valve including a PT port for allowing hydraulic oil to flow from the downstream side.

The control valve 176R is a spool valve including a PC port for allowing hydraulic oil to flow from the right main pump 14R to the arm cylinder 8 and a CT port for allowing hydraulic oil to flow from the arm cylinder 8 to the hydraulic oil tank.

The PT ports in each of the control valves 173, 174, 175L, and 175R are configured so that the opening area does not change regardless of the spool position. Specifically, the control valve 173 is configured so as not to limit the opening area of the PT port even when the spool is not in the neutral position, that is, when hydraulic oil is flowing into the swivel hydraulic motor 2A. Has been done. Therefore, hydraulic oil is supplied to the downstream side of the control valve 173 via this PT port. The same applies to the control valves 174, 175L, and 175R.

The variable load check valves 52 to 57 are valves that can switch communication / shutoff between each of the control valves 173, 174, 175L, 175R, 176L, and 176R and the main pump 14.

The switching valve 60 is a variable relief valve capable of switching whether or not to discharge the hydraulic oil discharged from the rod-side oil chamber of the boom cylinder 7 to the hydraulic oil tank. Specifically, the switching valve 60 communicates between the rod-side oil chamber of the boom cylinder 7 and the hydraulic oil tank when it is in the first position, and shuts off the communication when it is in the second position. Further, the switching valve 60 has a check valve that shuts off the flow of hydraulic oil from the hydraulic oil tank at the first position.

The switching valve 61 is a variable relief valve capable of switching whether or not to discharge the hydraulic oil discharged from the bottom side oil chamber of the boom cylinder 7 to the hydraulic oil tank. Specifically, the switching valve 61 communicates between the bottom oil chamber of the boom cylinder 7 and the hydraulic oil tank when it is in the first position, and shuts off the communication when it is in the second position. Further, the switching valve 61 has a check valve that shuts off the flow of hydraulic oil from the hydraulic oil tank at the first position.

As described above, in the example shown in FIG. 8, the control valve 177 is arranged in the bleed oil passage 41 configured to branch from the partial BF in the middle of the center bypass oil passage 40. The partial BF includes a partial BF1 located downstream of the control valve 171 corresponding to the left-running hydraulic motor 1A and a partial BF2 located downstream of the control valve 172 corresponding to the right-running hydraulic motor 1B. .. Therefore, the control valve 177 suppresses the influence of the control valve arranged downstream of the partial BF on the traveling operation, and controls the operability of the left traveling hydraulic motor 1A and the right traveling hydraulic motor 1B for driving the lower traveling body 1. The responsiveness can be improved.

Next, with reference to FIG. 9, the adjustment process executed by using the hydraulic system shown in FIG. 8 will be described. FIG. 9 shows a flowchart of the adjustment process. Apart from the unified bleed control, the controller 30 repeatedly executes this adjustment process at a predetermined control cycle.

First, the controller 30 detects the operating speed of the hydraulic actuator (step ST11). For example, the controller 30 detects the extension speed of the arm cylinder 8 based on the output of the arm angle sensor S2 when the arm closing operation is being performed. The controller 30 may derive the extension speed of the arm cylinder 8 based on the image captured by the front camera as the camera S6.

After that, the controller 30 determines whether or not the operating speed has fallen below the predetermined speed (step ST12). For example, the controller 30 determines whether or not the extension speed of the arm cylinder 8 calculated based on the arm angle detected by the arm angle sensor S2 has fallen below a predetermined speed. The predetermined speed is typically a value determined according to the lever operating amount of the arm operating lever 26A.

When it is determined that the operating speed is not lower than the predetermined speed (NO in step ST12), the controller 30 ends the current adjustment process without adjusting the opening area of the control valve 177 as the bleed valve.

On the other hand, when it is determined that the operating speed is lower than the predetermined speed (YES in step ST12), the controller 30 reduces the opening area of the control valve 177 as the bleed valve (step ST13). For example, when the controller 30 determines that the extension speed of the arm cylinder 8 is lower than the predetermined speed, the controller 30 reduces the opening area of the control valve 177.

If the extension speed of the arm cylinder 8 decreases when the lever operation amount of the arm operating lever 26A does not change, the hydraulic oil discharged by the main pump 14 becomes difficult to flow into the oil chamber on the bottom side of the arm cylinder 8, and the control valve 177 It becomes easier to flow toward. At this time, if the opening area of the control valve 177 is not reduced, the bleed flow rate, which is the flow rate of the hydraulic oil passing through the control valve 177, increases, and the flow rate of the hydraulic oil wastefully discharged to the hydraulic oil tank increases. Will end up. Further, as the bleed flow rate increases, the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the bottom oil chamber of the arm cylinder 8, decreases or disappears, and the movement of the arm 5 slows down or stops.

At this time, the controller 30 can suppress or prevent an increase in the bleed flow rate by reducing the opening area of the control valve 177 even when the lever operating amount of the arm operating lever 26A does not change, and the hydraulic oil tank can be used. It is possible to suppress or prevent an increase in the flow rate of the hydraulic oil that is wasted. Further, the controller 30 can suppress or prevent a decrease in the actuator flow rate by suppressing or prevent an increase in the bleed flow rate, and can prevent the movement of the arm 5 from slowing down or stopping.

In the example shown in FIG. 9, the controller 30 disables the negative control control when reducing the opening area of the control valve 177, as in the case of the example shown in FIG. That is, the controller 30 is configured to maintain the discharge amount of the main pump 14 at that time. When the opening area of the control valve 177 is reduced while the negative control control is enabled, the discharge amount of the main pump 14 increases as the bleed flow rate decreases, and as a result, the actuator flow rate becomes the operating speed of the hydraulic actuator. This is because the flow rate of the actuator before the speed falls below the predetermined speed becomes significantly larger than the flow rate of the actuator.

Further, in the example shown in FIG. 9, the controller 30 changes the degree of decrease in the opening area of the control valve 177 according to the magnitude of the operating speed of the hydraulic actuator. Specifically, the controller 30 is configured so that the lower the operating speed, the greater the degree of decrease, that is, the smaller the operating speed, the smaller the opening area. However, the degree of decrease in the opening area of the control valve 177 may be constant regardless of the magnitude of the operating speed.

Further, in the example shown in FIG. 9, when the controller 30 determines that the operating speed of the hydraulic actuator is lower than the predetermined speed, for example, when the extension speed of the arm cylinder 8 is determined to be lower than the predetermined speed, the control valve 177 is used. Reduces the opening area of. However, when the controller 30 determines that the fluctuation range of the extension speed of the arm cylinder 8 exceeds a predetermined width even though the lever operation amount of the arm operation lever 26A has not changed, the controller 30 determines the opening area of the control valve 177. It may be lowered.

Further, the controller 30 controls valve 177 when the rotation speed of the arm 5 is lower than the predetermined speed, for example, when the arm closing speed is lower than the predetermined speed, or when the arm opening speed is lower than the predetermined speed. It may be configured to reduce the opening area of the. Also in these cases, the predetermined speed is typically a value determined according to the lever operating amount of the arm operating lever 26A.

In the example shown in FIG. 9, the controller 30 is configured to reduce the opening area of the control valve 177 when it is determined that the operating speed of the hydraulic actuator is lower than the predetermined speed. However, when the controller 30 determines that the operating speed of the hydraulic actuator is lower than the predetermined speed and then determines that the operating device 26 is further operated in the direction in which the operating speed increases, the controller 30 opens the control valve 177. It may be configured to reduce the area. For example, the controller 30 determines that the extension speed of the arm cylinder 8 is lower than the predetermined speed when the arm closing operation for excavation is being performed, and then operates the lever in the arm closing direction of the arm operating lever 26A. When it is determined that the amount has increased, the opening area of the control valve 177 may be reduced. After confirming the operator's intention to push away the excavated object such as earth and sand that causes a decrease in the extension speed of the arm cylinder 8 and continue the arm closing operation, the arm cylinder reflects such an operator's intention. This is to increase the excavation force of 8. Conversely, this is to prevent the excavation force of the arm cylinder 8 from being increased even though the operator does not have such an intention. However, when the excavator 100 is operated by remote control, or when the excavator 100 is autonomously controlled, the determination as to whether or not the operating device 26 has been further operated may be omitted.

Next, with reference to FIG. 10, as the arm closing speed when the slope forming work as shown in FIG. 5 is performed, the opening area of the control valve 177L as a bleed valve, and the flow rate of hydraulic oil passing through the control valve 177L. The bleed flow rate of the above and the temporal transition of the actuator flow rate as the flow rate of the hydraulic oil passing through the PC port of the control valve 176L will be described. FIG. 10 shows an example of the temporal transition of the arm closing speed, the opening area of the control valve 177L, the bleed flow rate, and the actuator flow rate when the slope forming operation as shown in FIG. 5 is performed. The transition represented by the solid line shown in FIG. 10 indicates the transition when the adjustment process shown in FIG. 9 is executed, and the transition represented by the dotted line shown in FIG. 10 is the transition when the adjustment process shown in FIG. 9 is not executed. Shows the transition of. In the following description, the opening area of the control valve 177R, the bleed flow rate as the flow rate of the hydraulic oil passing through the control valve 177R among the hydraulic oil discharged by the right main pump 14R, and the right main pump 14R discharge. The same applies to the actuator flow rate as the flow rate of the hydraulic oil passing through the control valve 176R of the hydraulic oil.

When the toe of the bucket 6 hits the raised portion BP (see FIG. 5), the arm closing speed usually gradually decreases as the arm closing operation progresses, as shown in FIG. 10 (A), and at time t1. The predetermined speed Vth is reached.

When it is determined that the arm closing speed is lower than the predetermined speed Vth, the controller 30 outputs a control command to the control valve 177L and reduces the opening area of the control valve 177L. As a result, the opening area of the control valve 177L begins to decrease at time t1 as shown in FIG. 10B, and thereafter, the arm closing speed is controlled to be maintained at a predetermined speed Vth. The bleed flow rate, which is the flow rate of the hydraulic oil passing through the control valve 177L, becomes the desired flow rate, and the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the oil chamber on the bottom side of the arm cylinder 8, becomes the desired flow rate. This is to make it so. In the example of FIG. 10B, the controller 30 continuously reduces the opening area of the control valve 177L so that the arm closing speed is maintained at a predetermined speed Vth.

Specifically, the opening area of the control valve 177L is desired so that the bleed flow rate is the desired flow rate Qbt as shown in FIG. 10 (C) and the actuator flow rate is desired as shown in FIG. 10 (D). It is controlled so that the flow rate is Qat.

In the example shown in FIG. 10, the actuator flow rate is calculated as the flow rate of hydraulic oil passing through the PC port of the control valve 176L based on the differential pressure between the discharge pressure of the left main pump 14L and the arm bottom pressure. The discharge pressure of the left main pump 14L is detected based on the output of the left discharge pressure sensor 28L, and the arm bottom pressure is detected based on the output of the arm bottom pressure sensor S8B. The bleed flow rate is calculated as the flow rate of hydraulic oil passing through the control valve 177L based on the differential pressure between the discharge pressure of the left main pump 14L and the control pressure detected by the left control pressure sensor 19L. The discharge amount of the left main pump 14L is calculated as the sum of the actuator flow rate and the bleed flow rate. The discharge amount of the left main pump 14L is calculated based on the swash plate tilt angle corresponding to the control command for the left regulator 13L. The discharge amount of the left main pump 14L may be detected by the swash plate tilt angle sensor. The bleed flow rate may be calculated as a value obtained by subtracting the actuator flow rate from the discharge amount of the left main pump 14L. The actuator flow rate may be calculated as a value obtained by subtracting the bleed flow rate from the discharge amount of the left main pump 14L.

When the adjustment process is executed as described above, the opening area of the control valve 177L is when the adjustment process is not executed (see the dotted line in FIG. 10 (B)) as shown by the solid line in FIG. 10 (B). It is controlled to be smaller than that. When the adjustment process is not executed, the opening area of the control valve 177L is the opening area corresponding to the lever operating amount if the lever operating amount of the arm operating lever 26A is constant, as shown by the dotted line in FIG. 10 (B). This is because it is maintained at.

As shown by the solid line in FIG. 10 (C), the bleed flow rate is controlled to be smaller than that in the case where the adjustment process is not executed (see the dotted line in FIG. 10 (C)). This is because when the adjustment process is not executed, the bleed flow rate increases by the amount that the actuator flow rate decreases, as shown by the dotted line in FIG. 10 (C).

As shown by the solid line in FIG. 10 (D), the actuator flow rate is controlled to be larger than that in the case where the adjustment process is not executed (see the dotted line in FIG. 10 (D)). When the adjustment process is not executed, the actuator flow rate is as shown by the dotted line in FIG. 10 (D), and if the lever operation amount of the arm operating lever 26A is constant, the arm is closed as shown by the dotted line in FIG. 10 (A). This is because it becomes difficult to flow into the bottom side oil chamber of the arm cylinder 8 as the speed decreases, that is, it decreases as the arm bottom pressure increases.

As described above, the excavator 100 is configured to adjust the opening area of the control valve 177 according to the operating speed of the hydraulic actuator. With this configuration, the excavator 100 can smooth the movement of the hydraulic actuator when the operating speed of the hydraulic actuator changes during the operation of the hydraulic actuator. This is because the change in the flow rate of the hydraulic oil flowing into the hydraulic actuator can be suppressed without the operator changing the lever operation amount.

In the above-described embodiment, when the controller 30 determines that the operating speed of the hydraulic actuator has fallen below a predetermined speed, the controller 30 disables the negative control control to change the discharge amount of the main pump 14 before and after the determination. It is configured not to let you. This is to prevent the operating speed of the hydraulic actuator from changing before and after the determination.

For example, when the controller 30 determines that the extension speed of the arm cylinder 8 is lower than the predetermined speed while the slope forming work is being performed, the controller 30 does not change the discharge amount of the main pump 14 before and after the determination. It is configured in. This is to prevent the extension speed of the arm cylinder 8 from changing before and after the determination.

However, the controller 30 may be configured to increase or decrease the discharge amount of the main pump 14 after determining that the operating speed of the hydraulic actuator has fallen below a predetermined speed. This is to prevent the operating speed of the hydraulic actuator from changing before and after the determination. For example, this is to prevent the extension speed of the arm cylinder 8 from changing before and after the determination. Specifically, simply not changing the discharge amount of the main pump 14 before and after the determination cannot prevent the change in the extension speed of the arm cylinder 8 before and after the determination, such as when an external factor is large. This is because situations can occur. Therefore, if the decrease in the actuator flow rate cannot be compensated for by simply reducing the opening area of the control valve 177, the controller 30 may increase the discharge amount of the main pump 14, for example.

Alternatively, the controller 30 may be configured to reduce the discharge amount of the main pump 14 by a predetermined amount after determining that the operating speed of the hydraulic actuator has fallen below the predetermined speed. With this configuration, after determining that the operating speed of the hydraulic actuator has fallen below a predetermined speed due to an increase in load, the controller 30 maintains the smooth operation of the hydraulic actuator while operating the operating speed of the hydraulic actuator before the determination. By making the speed smaller than the speed by a predetermined size, the operator can be made to recognize that the load has increased.

Further, in the above example, when the controller 30 determines that the operating speed of the hydraulic actuator has fallen below a predetermined speed due to an increase in the load applied to the hydraulic actuator, the controller 30 reduces the opening area of the control valve 177 as a bleed valve. It is configured. This is to allow the hydraulic actuator to operate continuously and smoothly while preventing the hydraulic actuator from becoming excessively slow even when the load applied to the hydraulic actuator increases. However, even if the controller 30 is configured to increase the opening area of the control valve 177 as a bleed valve when it is determined that the operating speed of the hydraulic actuator exceeds a predetermined speed due to a decrease in the load applied to the hydraulic actuator. Good. This is to allow the hydraulic actuator to operate continuously and smoothly while preventing the hydraulic actuator from moving excessively fast even when the load applied to the hydraulic actuator is reduced.

As described above, the excavator 100 according to the embodiment of the present invention is an oil capable of supplying an attachment, a hydraulic actuator, a main pump 14 as a hydraulic pump, and hydraulic oil discharged by the main pump 14 to a plurality of hydraulic actuators. It has a passage 42, a plurality of control valves 171 to 176 arranged in the oil passage 42, and a control valve 177 as a bleed valve arranged in the oil passage 42. The excavator 100 is configured to adjust the opening of the control valve 177 according to the load applied to the hydraulic actuator.

With this configuration, the excavator 100 can smooth the movement of the hydraulic actuator when the load applied to the hydraulic actuator changes during the operation of the hydraulic actuator. When the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the hydraulic actuator, decreases and the bleed flow rate, which is the flow rate passing through the control valve 177, increases, the decrease in the actuator flow rate can be suppressed by reducing the bleed flow rate. Is. That is, even when the load applied to the hydraulic actuator increases, the actuator flow rate before the load increases can be secured. Alternatively, when the actuator flow rate increases and the bleed flow rate decreases, the increase in the actuator flow rate can be suppressed by increasing the bleed flow rate.

As a result, the excavator 100 can improve the operability. For example, this is because the shock caused by the sudden movement of the hydraulic actuator due to the sudden decrease in the load applied to the hydraulic actuator can be reduced. Further, the excavator 100 can realize effective utilization of hydraulic energy and energy saving. For example, this is because it is possible to suppress a sudden increase in the bleed flow rate due to a sudden decrease in the load applied to the hydraulic actuator.

The excavator 100 is configured to reduce the opening of the control valve 177 when, for example, it is determined that the load applied to the hydraulic actuator is higher than a predetermined value. Specifically, when the excavator 100 determines that the load applied to the hydraulic actuator is higher than the predetermined value, the opening of the control valve 177 is smaller than when it is not determined that the load applied to the hydraulic actuator is higher than the predetermined value. It is configured to do. With this configuration, the excavator 100 can smooth the movement of the hydraulic actuator when the load applied to the hydraulic actuator increases during the operation of the hydraulic actuator.

The excavator 100 may be configured to derive a load applied to the hydraulic actuator based on, for example, the pressure of the hydraulic oil flowing into the hydraulic actuator or the operating speed of the hydraulic actuator. For example, the excavator 100 may be configured to derive the load applied to the arm cylinder 8 based on the arm bottom pressure detected by the arm bottom pressure sensor S8B. Alternatively, the excavator 100 may be configured to derive the load applied to the arm cylinder 8 based on the arm angle detected by the arm angle sensor S2. With this configuration, the excavator 100 can easily and accurately derive the load applied to the hydraulic actuator.

The excavator 100 may be configured to calculate the flow rate of the hydraulic oil passing through the control valve 177 from, for example, the differential pressure between the pressure of the hydraulic oil flowing into the hydraulic actuator and the discharge pressure of the main pump 14. .. The excavator 100 may be configured to reduce the opening of the control valve 177 according to the bleed flow rate, which is the flow rate of the hydraulic oil passing through the control valve 177. With this configuration, the excavator 100 can appropriately control the opening of the control valve 177 by calculating the bleed flow rate easily and accurately.

The excavator 100 has an actuator flow rate, which is the flow rate of hydraulic oil flowing into the hydraulic actuator, an operating speed of the hydraulic actuator, or a bleed, which is the flow rate of hydraulic oil passing through the control valve 177, before and after adjusting the opening of the control valve 177. The opening of the control valve 177 may be adjusted so that the flow rate becomes constant. With this configuration, the excavator 100 can continuously operate the hydraulic actuator at substantially the same operating speed even when the load applied to the hydraulic actuator changes.

The excavator 100 may be configured to calculate the operating speed of the hydraulic actuator based on the output of the sensor. The sensor is, for example, a boom angle sensor S1, an arm angle sensor S2, a bucket angle sensor S3, or a turning angular velocity sensor S5. For example, the excavator 100 may be configured to calculate the expansion / contraction speed of the arm cylinder 8 based on the output of the arm angle sensor S2. Alternatively, the excavator 100 may be configured to calculate the rotation speed of the turning hydraulic motor 2A based on the output of the turning angular velocity sensor S5. Alternatively, the excavator 100 may be configured to calculate the operating speed of the hydraulic actuator based on the output of an image sensor such as the camera S6. With this configuration, the excavator 100 can easily and accurately calculate the operating speed of the hydraulic actuator.

The excavator 100 may be configured to change the discharge amount of the main pump 14 after determining the magnitude of the load applied to the hydraulic actuator. With this configuration, the excavator 100 makes a slight movement of the hydraulic actuator even when, for example, a control for smoothing the movement of the hydraulic actuator when the load applied to the hydraulic actuator changes during the operation of the hydraulic actuator is executed. By slowing down to, the operator can be made aware that the load applied to the hydraulic actuator has changed. Alternatively, even if the excavator 100 cannot smooth the movement of the hydraulic actuator only by adjusting the opening area of the control valve 177, the excavator 100 can additionally change the discharge amount of the main pump 14 to reduce the pressure. The movement of the actuator can be smoothed.

The control valve 177 may be configured to, for example, realize a unified bleed flow rate suitable for a combination of movement amounts of the plurality of control valves. For example, the control valve 177L shown in FIG. 3 is configured to realize a unified bleed flow rate suitable for each combination of the movement amounts of the control valves 171, 173, 175L, and 176L as spool valves. Further, the control valve 177R shown in FIG. 3 is configured to realize a unified bleed flow rate suitable for each combination of the movement amounts of the control valves 172, 174, 175R, and 176R as spool valves. Further, the control valve 177L shown in FIG. 8 is configured to realize a unified bleed flow rate suitable for each combination of the movement amounts of the control valves 173, 175L and 176L as spool valves. Further, the control valve 177R shown in FIG. 8 is configured to realize a unified bleed flow rate suitable for each combination of the movement amounts of the control valves 174, 175R and 176R as spool valves. With this configuration, the control valve 17 can reduce the pressure loss as compared with the configuration in which the bleed flow rate is adjusted by each of the plurality of control valves.

However, the control valve 177 as a bleed valve has two or more configured to realize a unified bleed flow rate suitable for the combination of the movement amounts of at least two control valves among the control valves 171 to 176. It may be a combination of bleed valves.

Alternatively, the control valve 177 as a bleed valve may be a combination of eight bleed valves capable of individually adjusting the bleed flow rate of each of the eight control valves 171 to 176.

The preferred embodiment of the present invention has been described in detail above. However, the present invention is not limited to the embodiments described above. Various modifications or substitutions can be applied to the above-described embodiments without departing from the scope of the present invention. Also, the features described separately can be combined as long as there is no technical conflict.

For example, in the above-described embodiment, a hydraulic operation system including a hydraulic pilot circuit is disclosed. For example, in the hydraulic pilot circuit related to the arm operating lever 26A as shown in FIG. 3, the hydraulic oil supplied from the pilot pump 15 to the arm operating lever 26A is opened and closed by tilting the arm operating lever 26A in the opening direction. It is supplied to the pilot port of the control valve 176 at a flow rate corresponding to the opening degree of the control valve. Alternatively, in the hydraulic pilot circuit related to the boom operating lever 26B, the hydraulic oil supplied from the pilot pump 15 to the boom operating lever 26B is set to the opening degree of the remote control valve that is opened and closed by tilting the boom operating lever 26B in the upward direction. It is supplied to the pilot port of the control valve 175 at a corresponding flow rate.

However, an electric operation system provided with an electric pilot circuit may be adopted instead of a hydraulic operation system provided with such a hydraulic pilot circuit. In this case, the lever operation amount of the electric operation lever in the electric operation system is input to the controller 30 as an electric signal, for example. Further, an electromagnetic valve is arranged between the pilot pump 15 and the pilot port of each control valve. The solenoid valve is configured to operate in response to an electrical signal from the controller 30. With this configuration, when a manual operation using an electric operation lever is performed, the controller 30 moves each control valve by controlling the solenoid valve by an electric signal corresponding to the lever operation amount to increase or decrease the pilot pressure. be able to. Each control valve may be composed of an electromagnetic spool valve. In this case, the electromagnetic spool valve operates in response to an electric signal from the controller 30 corresponding to the lever operation amount of the electric operation lever.

FIG. 11 shows a configuration example of an electric operation system. Specifically, the electric operation system shown in FIG. 11 is an example of an arm operation system for expanding and contracting the arm cylinder 8, and mainly serves as a pilot pressure actuated control valve 17 and an electric operation lever. It is composed of an arm operation lever 26A, a controller 30, an electromagnetic valve 62 for arm closing operation, and an electromagnetic valve 63 for arm opening operation. The electric operation system shown in FIG. 11 includes a turning operation system for turning the upper turning body 3, a boom operating system for moving the boom 4 up and down, a bucket operating system for opening and closing the bucket 6, and a lower traveling body. Similarly, it can be applied to a traveling operation system or the like for moving forward / backward.

The pilot pressure actuated type control valve 17 relates to a control valve 171 (see FIG. 3) relating to the left traveling hydraulic motor 1A, a control valve 172 (see FIG. 3) relating to the right traveling hydraulic motor 1B, and a turning hydraulic motor 2A. Control valve 173 (see FIG. 3), control valve 175 for boom cylinder 7 (see FIG. 3), control valve 176 for arm cylinder 8 (see FIG. 3), and control valve 174 for bucket cylinder 9 (see FIG. 3). See.) Etc. are included. The solenoid valve 62 is configured to be able to adjust the pressure of hydraulic oil in the oil passage connecting the pilot pump 15 and the closed side pilot port of the control valve 176. The solenoid valve 63 is configured to be able to adjust the pressure of hydraulic oil in the oil passage connecting the pilot pump 15 and the open side pilot port of the control valve 176.

When a manual operation is performed, the controller 30 outputs an arm closing operation signal (electric signal) or an arm opening operation signal (electric signal) according to an operation signal (electric signal) output by the operation signal generation unit of the arm operation lever 26A. Generate. The operation signal output by the operation signal generation unit of the arm operation lever 26A is an electric signal that changes according to the operation amount and the operation direction of the arm operation lever 26A.

Specifically, when the arm operating lever 26A is operated in the closing direction, the controller 30 outputs an arm closing operation signal (electric signal) corresponding to the lever operation amount to the solenoid valve 62. The solenoid valve 62 operates in response to the arm closing operation signal (electric signal) and controls the pilot pressure as the arm closing operation signal (pressure signal) acting on the closing side pilot port of the control valve 176. Similarly, when the arm operating lever 26A is operated in the opening direction, the controller 30 outputs an arm opening operation signal (electric signal) corresponding to the lever operation amount to the solenoid valve 63. The solenoid valve 63 operates in response to the arm opening operation signal (electric signal) and controls the pilot pressure as the arm opening operation signal (pressure signal) acting on the opening side pilot port of the control valve 176.

When executing autonomous control, for example, the controller 30 responds to an autonomous operation signal (electric signal) instead of responding to an operation signal (electric signal) output by the operation signal generation unit of the arm operation lever 26A. (Electrical signal) or arm opening operation signal (electrical signal) is generated. The autonomous operation signal is a signal generated regardless of the operation amount and operation direction of the arm operation lever 26A. The autonomous operation signal may be an electric signal generated by the controller 30, or may be an electric signal generated by a control device or the like other than the controller 30.

Further, in the above-described embodiment, the adjustment process is used to smooth the arm closing operation during the slope forming operation, but the boom raising operation during the suspension operation by the excavator 100 operating in the crane mode is smoothed. May be used to. In this case, the controller 30 executes the adjustment process to smooth the boom raising operation, so that, for example, the amount of lever operation in the boom raising direction of the boom operating lever 26B by the operator when lifting the suspended load is excessive. The increase can be suppressed. As a result, the controller 30 can prevent the boom 4 from suddenly rising, for example, when the suspended load is lifted. Further, the adjustment process may be used, for example, to smooth the turning operation during the leveling operation. In this case, the controller 30 executes the adjustment process to smooth the turning operation, for example, by the operator when pushing away the earth and sand on the side surface of the bucket 6 while turning the upper swing body 3 (excavation attachment). It is possible to suppress an excessive increase in the amount of lever operation in the turning direction of the turning operation lever. As a result, the controller 30 can prevent the upper swivel body 3 (excavation attachment) from turning sharply when, for example, earth and sand are pushed away. Immediately after the earth and sand are pushed away by the swivel operation during the leveling work, the load applied to the swivel hydraulic motor 2A suddenly decreases, so that the controller 30 typically increases the opening area of the control valve 177. Let me. However, immediately after the suspended load is lifted by the boom raising operation during the lifting operation, the load applied to the boom cylinder 7 does not suddenly decrease, so that the controller 30 typically maintains the opening area of the control valve 177 at that time. To be done.

Further, in the above-described embodiment, the discharge amount of the main pump 14 is configured to be controlled by negative control control. However, the discharge amount of the main pump 14 may be configured to be controlled by another control method such as positive control control or load sensing control.

1 ... Lower traveling body 1A ... Left traveling hydraulic motor 1B ... Right traveling hydraulic motor 2 ... Swivel mechanism 2A ... Swivel hydraulic motor 3 ... Upper swivel body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10 ... Cabin 11 ... Engine 13 ... Regulator 14 ... Main pump 15 ... Pilot pump 17 ... Control valve 18 ... Squeeze 19 ... Control pressure sensor 26 ... Operating device 26A ... Arm operating lever 26B ... Boom operating lever 28 ... Discharge pressure Sensor 29: Operating pressure sensor 29A: Arm operating pressure sensor 29B: Boom operating pressure sensor 30: Controller 31: Solenoid valve 40: Center bypass oil passage 41: Bleed oil passage 42 ... Oil passage 43 ... Oil passage 50 ... Relief valve 51 ... Check valve 52 to 57 ... Variable load check valve 60, 61 ... Switching valve 62, 63 ... Solenoid valve 100 ... Excavator 170-177 ... Control valve S1 ... Boom angle sensor S2 ... Arm angle sensor S3 ... Bucket angle sensor S4 ... Aircraft tilt sensor S5 ... Turning angle speed sensor S6・ ・ Camera S7B ・ ・ ・ Boom bottom pressure sensor S7R ・ ・ ・ Boom rod pressure sensor S8B ・ ・ ・ Arm bottom pressure sensor S8R ・ ・ ・ Arm rod pressure sensor S9B ・ ・ ・ Bucket bottom pressure sensor S9R ・ ・ ・ Bucket rod pressure Sensor

Claims (9)

Attachment and
With hydraulic actuator,
With a hydraulic pump
An oil passage capable of supplying hydraulic oil discharged by the hydraulic pump to the plurality of hydraulic actuators, and
A plurality of control valves arranged in the oil passage and
With a bleed valve arranged in the oil passage,
The opening of the bleed valve is adjusted according to the load applied to the hydraulic actuator.
Excavator. When it is determined that the load is higher than a predetermined value, the opening of the bleed valve is reduced.
The excavator according to claim 1. When it is determined that the load is higher than the predetermined value, the opening of the bleed valve is made smaller than when it is not determined that the load is higher than the predetermined value.
The excavator according to claim 1 or 2. The load is derived based on the pressure of the hydraulic oil flowing into the hydraulic actuator or the operating speed of the hydraulic actuator.
The excavator according to any one of claims 1 to 3. The flow rate of the hydraulic oil passing through the bleed valve is calculated from the differential pressure between the pressure of the hydraulic oil flowing into the hydraulic actuator and the discharge pressure of the hydraulic pump, and according to the flow rate of the hydraulic oil passing through the bleed valve. To reduce the opening of the bleed valve,
The excavator according to any one of claims 1 to 4. Before and after the adjustment of the opening of the bleed valve, the actuator flow rate, which is the flow rate of the hydraulic oil flowing into the hydraulic actuator, the operating speed of the hydraulic actuator, or the bleed flow rate, which is the flow rate of the hydraulic oil passing through the bleed valve, is Adjust the opening of the bleed valve so that it is constant.
The excavator according to any one of claims 1 to 5. The operating speed of the hydraulic actuator is calculated based on the output of the sensor.
The excavator according to any one of claims 1 to 6. After determining the magnitude of the load, the discharge amount of the hydraulic pump is changed.
The excavator according to any one of claims 1 to 7. The bleed valve is configured to uniformly control the bleed flow rate suitable for the movement amount of each of the plurality of control valves.
The excavator according to any one of claims 1 to 8.

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