Shovel

Abstract

To provide a shovel improved in operability.SOLUTION: A shovel includes a hydraulic actuator, a hydraulic pump, a control valve for controlling the flow rate of hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator, an electromagnetic proportional valve for controlling a secondary pressure input to the control valve, and a controller to which the operation amount of an operation lever is input, and that controls the electromagnetic proportional valve, wherein the controller determines a command secondary pressure on the basis of the operation amount of the operation lever, at the input operation amount of the operation lever less than a predetermined operation amount, restricts an increase amount of the command secondary pressure, and determines the command secondary pressure, at the input operation amount of the operation lever equal to or more than the predetermined operation amount, and controls the current value of the electromagnetic proportional valve, on the basis of the command secondary pressure.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a shovel.

Background Art

[0002] In Patent Document 1, in the relationship between the lever operation amount and the target value of the control current of the electromagnetic proportional valve that generates the pilot pressure of the direction control valve, when the lever operation amount is greater than a predetermined operation amount and less than the maximum operation amount, the target value of the control current increases to a predetermined current in proportion to the increase in the lever operation amount. When the lever operation amount is 100[%] which is the maximum operation amount, it is described that the target value of the control current rapidly rises from the predetermined current to the maximum current (see particularly FIG. 8).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, near the maximum operation amount, the command value to the electromagnetic proportional valve rapidly rises with respect to the lever operation amount, so the secondary pressure supplied to the direction control valve also changes rapidly. For this reason, the operation of the hydraulic actuator also changes rapidly, and the operability of the shovel deteriorates.

[0005] Therefore, in view of the above problems, an object is to provide a shovel that improves operability.

Means for Solving the Problems

[0006] In order to achieve the above object, an excavator according to an embodiment of the present invention includes a hydraulic actuator, a hydraulic pump, a control valve for controlling the flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator, an electromagnetic proportional valve for controlling the secondary pressure input to the control valve, and a controller that receives the operation amount of an operation lever and controls the electromagnetic proportional valve. The controller determines a commanded secondary pressure based on the operation amount of the input operation lever when the operation amount of the input operation lever is less than a predetermined operation amount, and determines the commanded secondary pressure by limiting the increase amount of the commanded secondary pressure when the operation amount of the input operation lever is greater than or equal to the predetermined operation amount, and controls the current value of the electromagnetic proportional valve based on the commanded secondary pressure.

Effect of the Invention

[0007] According to the above-described embodiment, an excavator with improved operability can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0009] First, with reference to FIG. 1, an excavator 100 as an excavating machine according to an embodiment of the present invention will be described. FIG. 1 is a side view of the excavator 100.

[0010] In the present embodiment, the lower traveling body 1 of the excavator 100 includes crawlers. The crawlers are driven by a traveling hydraulic motor 2M as a traveling actuator mounted on the lower traveling body 1. Specifically, the crawlers include a left crawler and a right crawler. The left crawler is driven by a left traveling hydraulic motor 2ML, and the right crawler is driven by a right traveling hydraulic motor 2MR.

[0011] The upper revolving body 3 is rotatably mounted on the lower traveling body 1 via a slewing mechanism 2. The slewing mechanism 2 is driven by a slewing hydraulic motor 2A as a slewing actuator mounted on the upper revolving body 3. However, the slewing actuator may be a slewing electric generator as an electric actuator.

[0012] A boom 4 is attached to the upper slewing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 as an end attachment is attached to the tip of the arm 5. The boom 4, the arm 5, and the bucket 6 constitute an attachment AT which is an example of an attachment. The boom 4 is driven by a boom cylinder 7, the arm 5 is driven by an arm cylinder 8, and the bucket 6 is driven by a bucket cylinder 9. The boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9 constitute an attachment actuator. In the example shown in FIG. 1, the bucket 6 is an excavation bucket, but it may be a skeleton bucket or a (debris removal bucket). Further, the bucket 6 may be provided with a bucket tilt mechanism.

[0013] A cabin 10 as a driver's cab is provided in the upper slewing body 3, and a power source such as an engine 11 is mounted. An operating device 26, a controller 30, etc. are provided inside the cabin 10. Further, a space recognition device 70, etc. are attached to the upper slewing body 3. In this book, for convenience, the side of the upper slewing body 3 where the attachment AT is attached is defined as the front, and the side where the counterweight is attached is defined as the rear.

[0014] The space recognition device 70 is configured to recognize an object existing in the three-dimensional space around the excavator 100. Further, the space recognition device 70 may be configured to calculate the distance to the object recognized from the space recognition device 70 or the excavator 100. The space recognition device 70 includes, for example, an ultrasonic sensor, a millimeter wave radar, an imaging device, a LIDAR, a distance image sensor, an infrared sensor, etc., or any combination thereof. The imaging device is, for example, a monocular camera or a stereo camera. In the present embodiment, the space recognition device 70 includes a front sensor 70F attached to the front end of the upper surface of the cab 10, a rear sensor 70B attached to the rear end of the upper surface of the upper swing body 3, a left sensor 70L attached to the left end of the upper surface of the upper swing body 3, and a right sensor (not shown) attached to the right end of the upper surface of the upper swing body 3. An upper sensor for recognizing an object existing in the space above the upper swing body 3 may be attached to the excavator 100.

[0015] The operating device 26 is a device used by an operator for operating an actuator. The operating device 26 includes, for example, an operating lever and an operating pedal. The actuator includes at least one of a hydraulic actuator and an electric actuator.

[0016] The controller 30 is a control device for controlling the excavator 100. In the present embodiment, the controller 30 is composed of a computer including a CPU, a volatile memory device, a non-volatile memory device, and the like. Then, the controller 30 reads out a program corresponding to each function from the non-volatile memory device and loads it into the volatile memory device, and causes the CPU to execute the corresponding process. Each function includes, for example, a machine guidance function for guiding (guiding) the manual operation of the excavator 100 by the operator, and a machine control function for assisting the manual operation of the excavator 100 by the operator or operating the excavator 100 automatically or autonomously. The controller 30 may include a contact avoidance function for automatically or autonomously operating or stopping the excavator 100 in order to avoid contact between an object existing within the monitoring range around the excavator 100 and the excavator 100. The monitoring of the objects around the excavator 100 is performed not only within the monitoring range but also outside the monitoring range.

[0017] Next, referring to FIG. 2, a configuration example of the hydraulic system mounted on the excavator 100 will be described. FIG. 2 is a diagram showing a configuration example of the hydraulic system mounted on the excavator 100. In FIG. 2, the mechanical power transmission system, the hydraulic oil line, the pilot line, and the electric control system are shown by double lines, solid lines, broken lines, and dotted lines, respectively.

[0018] The hydraulic system of the excavator 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve unit 17, an operating device 26, a discharge pressure sensor 28, an operation sensor 29, and a controller 30, etc.

[0019] In FIG. 2, the hydraulic system is configured such that hydraulic oil can be circulated from the main pump 14 driven by the engine 11 to the hydraulic oil tank through the center bypass pipeline 40 or the parallel pipeline 42.

[0020] The engine 11 is the drive source of the excavator 100. In the present embodiment, the engine 11 is, for example, a diesel engine that operates so as to maintain a predetermined rotational speed. The output shaft of the engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15, respectively.

[0021] The main pump 14 is configured to be able to supply hydraulic oil to the control valve unit 17 via a hydraulic oil line. In the present embodiment, the main pump 14 is a swash plate type variable displacement hydraulic pump.

[0022] The regulator 13 is configured to be able 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.

[0023] The pilot pump 15 is an example of a pilot pressure generating device and is configured to be able to supply hydraulic oil to hydraulic control devices via a pilot line. In the present embodiment, the pilot pump 15 is a fixed displacement hydraulic pump. However, the pilot pressure generating device may be realized by the main pump 14. That is, in addition to the function of supplying hydraulic oil to the control valve unit 17 via a hydraulic oil line, the main pump 14 may have a function of supplying hydraulic oil to various hydraulic control devices via a pilot line. In this case, the pilot pump 15 may be omitted.

[0024] The control valve unit 17 is a hydraulic control device that controls the hydraulic system in the excavator 100. In this embodiment, the control valve unit 17 includes control valves (also referred to as direction control valves) 171 to 176. The control valve 175 includes a control valve 175L and a control valve 175R, and the control valve 176 includes a control valve 176L and a control valve 176R. The control valve unit 17 is configured to selectively supply the hydraulic oil discharged by 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 control, for example, 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 actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left travel hydraulic motor 2ML, a right travel hydraulic motor 2MR, and a swing hydraulic motor 2A.

[0025] The operating device 26 is configured such that an operator can operate the actuator. In this embodiment, the operating device 26 includes a hydraulic actuator operating device configured such that the operator can operate the hydraulic actuator. Specifically, the hydraulic actuator operating device is configured to supply the hydraulic oil discharged by the pilot pump 15 to the pilot ports of the corresponding control valves 171 to 176 in the control valve unit 17 through a proportional valve 31 controlled by the controller 30 via a pilot line. The pressure (pilot pressure) of the hydraulic oil supplied to each of the pilot ports is a pressure corresponding to the operating direction and operating amount of the operating device 26 corresponding to each of the hydraulic actuators.

[0026] The discharge pressure sensor 28 is configured to detect the discharge pressure of the main pump 14. In this embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

[0027] The operation sensor 29 is configured to be able to detect the content of the operation of the operation device 26 by the operator. In the present embodiment, the operation sensor 29 detects the operation direction and operation amount of the operation device 26 corresponding to each actuator, and outputs the detected values to the controller 30.

[0028] The main pump 14 includes a left main pump 14L and a right main pump 14R. The left main pump 14L circulates the hydraulic oil to the hydraulic oil tank through the left center bypass pipeline 40L or the left parallel pipeline 42L, and the right main pump 14R circulates the hydraulic oil to the hydraulic oil tank through the right center bypass pipeline 40R or the right parallel pipeline 42R.

[0029] The left center bypass pipeline 40L is a hydraulic oil line that passes through the control valves 171, 173, 175L, and 176L arranged in the control valve unit 17. The right center bypass pipeline 40R is a hydraulic oil line that passes through the control valves 172, 174, 175R, and 176R arranged in the control valve unit 17.

[0030] The control valve 171 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the left main pump 14L to the left travel hydraulic motor 2ML and to discharge the hydraulic oil discharged by the left travel hydraulic motor 2ML to the hydraulic oil tank.

[0031] The control valve 172 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the right main pump 14R to the right travel hydraulic motor 2MR and to discharge the hydraulic oil discharged by the right travel hydraulic motor 2MR to the hydraulic oil tank.

[0032] The control valve 173 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged by the left main pump 14L to the swing hydraulic motor 2A and to discharge the hydraulic oil discharged by the swing hydraulic motor 2A to the hydraulic oil tank.

[0033] The control valve 174 is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the right main pump 14R to the bucket cylinder 9 and to discharge the hydraulic oil in the bucket cylinder 9 to the hydraulic oil tank.

[0034] The control valve 175L is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the left main pump 14L to the boom cylinder 7. The control valve 175R is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the right main pump 14R to the boom cylinder 7 and to discharge the hydraulic oil in the boom cylinder 7 to the hydraulic oil tank.

[0035] The control valve 176L is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the left main pump 14L to the arm cylinder 8 and to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank.

[0036] The control valve 176R is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the right main pump 14R to the arm cylinder 8 and to discharge the hydraulic oil in the arm cylinder 8 to the hydraulic oil tank.

[0037] The left parallel pipeline 42L is a hydraulic oil line parallel to the left center bypass pipeline 40L. The left parallel pipeline 42L can supply hydraulic oil to a downstream control valve when the flow of hydraulic oil through the left center bypass pipeline 40L is restricted or blocked by any one of the control valves 171, 173, and 175L. The right parallel pipeline 42R is a hydraulic oil line parallel to the right center bypass pipeline 40R. The right parallel pipeline 42R can supply hydraulic oil to a downstream control valve when the flow of hydraulic oil through the right center bypass pipeline 40R is restricted or blocked by any one of the control valves 172, 174, and 175R.

[0038] The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L controls the discharge amount of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L according to the discharge pressure of the left main pump 14L. Specifically, for example, the left regulator 13L adjusts the swash plate tilt angle of the left main pump 14L in response to an increase in the discharge pressure of the left main pump 14L to decrease the discharge amount. The same applies to the right regulator 13R. This is to ensure that the absorption power (absorption horsepower) of the main pump 14, represented by the product of the discharge pressure and the discharge amount, does not exceed the output power (output horsepower) of the engine 11.

[0039] The operating device 26 includes a left operating lever 26L, a right operating lever 26R, and a traveling lever 26D. The traveling lever 26D includes a left traveling lever 26DL and a right traveling lever 26DR.

[0040] The left operating lever 26L is used for the turning operation and the operation of the arm 5. When the left operating lever 26L is operated in the front-rear direction, it uses the hydraulic oil discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 176. When the left operating lever 26L is operated in the left-right direction, it uses the hydraulic oil discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 173.

[0041] Specifically, when the left operating lever 26L is operated in the arm closing direction, it introduces hydraulic oil into the right pilot port of the control valve 176L and also introduces hydraulic oil into the left pilot port of the control valve 176R. When the left operating lever 26L is operated in the arm opening direction, it introduces hydraulic oil into the left pilot port of the control valve 176L and also introduces hydraulic oil into the right pilot port of the control valve 176R. When the left operating lever 26L is operated in the left turning direction, it introduces hydraulic oil into the left pilot port of the control valve 173, and when it is operated in the right turning direction, it introduces hydraulic oil into the right pilot port of the control valve 173.

[0042] In the example shown in FIG. 2, the left operation lever 26L functions as an arm operation lever when operated in the front-rear direction, and functions as a turning operation lever when operated in the left-right direction.

[0043] The right operation lever 26R is used for the operation of the boom 4 and the operation of the bucket 6. When the right operation lever 26R is operated in the front-rear direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 175. When the right operation lever 26R is operated in the left-right direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 174.

[0044] Specifically, when the right operation lever 26R is operated in the boom lowering direction, it introduces hydraulic oil into the right pilot port of the control valve 175R. When the right operation lever 26R is operated in the boom raising direction, it introduces hydraulic oil into the left pilot port of the control valve 175L and also into the right pilot port of the control valve 175R. When the right operation lever 26R is operated in the bucket closing direction, it introduces hydraulic oil into the left pilot port of the control valve 174, and when the right operation lever 26R is operated in the bucket opening direction, it introduces hydraulic oil into the right pilot port of the control valve 174.

[0045] In the example shown in FIG. 2, the right operation lever 26R functions as a boom operation lever when operated in the front-rear direction, and functions as a bucket operation lever when operated in the left-right direction.

[0046] The travel lever 26D is used for operating the crawlers. Specifically, the left travel lever 26DL is used for operating the left crawler. It may be configured to be interlocked with the left travel pedal. When the left travel lever 26DL is operated in the front-rear direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 171. The right travel lever 26DR is used for operating the right crawler. It may be configured to be interlocked with the right travel pedal. When the right travel lever 26DR is operated in the front-rear direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 172.

[0047] The discharge pressure sensor 28 includes a discharge pressure sensor 28L and a discharge pressure sensor 28R. The discharge pressure sensor 28L detects the discharge pressure of the left main pump 14L and outputs the detected value to the controller 30. The same applies to the discharge pressure sensor 28R.

[0048] The operation sensor 29 includes operation sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. The operation sensor 29LA detects the content of the front-rear direction operation of the left operation lever 26L by the operator and outputs the detected value to the controller 30. The content of the operation is, for example, the lever operation direction, the lever operation amount (lever operation angle), etc.

[0049] Similarly, the operation sensor 29LB detects the content of the left - right direction operation on the left operation lever 26L by the operator and outputs the detected value to the controller 30. The operation sensor 29RA detects the content of the front - rear direction operation on the right operation lever 26R by the operator and outputs the detected value to the controller 30. The operation sensor 29RB detects the content of the left - right direction operation on the right operation lever 26R by the operator and outputs the detected value to the controller 30. The operation sensor 29DL detects the content of the front - rear direction operation on the left travel lever 26DL by the operator and outputs the detected value to the controller 30. The operation sensor 29DR detects the content of the front - rear direction operation on the right travel lever 26DR by the operator and outputs the detected value to the controller 30.

[0050] The controller 30 receives the output of the operation sensor 29, outputs a control command to the regulator 13 as necessary, and changes the discharge amount of the main pump 14. Also, the controller 30 receives the output of the control pressure sensor 19 provided upstream of the throttle 18, outputs a control command to the regulator 13 as necessary, and changes the discharge amount of the main pump 14. The throttle 18 includes a left throttle 18L and a right throttle 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R.

[0051] In the left center bypass pipeline 40L, a left throttle valve 18L is arranged between the most downstream control valve 176L and the hydraulic oil tank. Therefore, the flow of the hydraulic oil discharged by the left main pump 14L is restricted by the left throttle valve 18L. And the left throttle valve 18L generates a control pressure for controlling the left regulator 13L. The left control pressure sensor 19L is a sensor for detecting this control pressure, and outputs the detected value to the controller 30. The controller 30 controls the discharge amount of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L according to this control pressure. The controller 30 decreases the discharge amount of the left main pump 14L as this control pressure increases, and increases the discharge amount of the left main pump 14L as this control pressure decreases. The discharge amount of the right main pump 14R is controlled in the same way.

[0052] Specifically, as shown in FIG. 2, in the case of the standby state where none of the hydraulic actuators in the excavator 100 are operated, the hydraulic oil discharged by the left main pump 14L reaches the left throttle valve 18L through the left center bypass pipeline 40L. And the flow of the hydraulic oil discharged by the left main pump 14L increases the control pressure generated upstream of the left throttle valve 18L. As a result, the controller 30 decreases the discharge amount of the left main pump 14L to the allowable minimum discharge amount, and suppresses the pressure loss (pumping loss) when the discharged hydraulic oil passes through the left center bypass pipeline 40L. On the other hand, when any hydraulic actuator is operated, the hydraulic oil discharged by the left main pump 14L flows into the operated hydraulic actuator through the control valve corresponding to the operated hydraulic actuator. And the flow of the hydraulic oil discharged by the left main pump 14L decreases or disappears the amount reaching the left throttle valve 18L, and decreases the control pressure generated upstream of the left throttle valve 18L. As a result, the controller 30 increases the discharge amount of the left main pump 14L, circulates sufficient hydraulic oil to the operated hydraulic actuator, and ensures the driving of the operated hydraulic actuator. Note that the controller 30 controls the discharge amount of the right main pump 14R in the same way.

[0053] With the above configuration, in the standby state, the hydraulic system of FIG. 2 can suppress the wasteful energy consumption in the main pump 14. The wasteful energy consumption includes the pumping loss generated by the hydraulic oil discharged from the main pump 14 in the center bypass pipeline 40. Further, when operating the hydraulic actuator, the hydraulic system of FIG. 2 can surely supply the necessary and sufficient hydraulic oil from the main pump 14 to the hydraulic actuator to be operated.

[0054] That is, the controller 30 controls the regulator 13 so that the smaller of the first discharge amount calculated so that the absorption power (absorption horsepower) of the main pump 14 represented by the product of the discharge pressure and the discharge amount does not exceed the output power (output horsepower) of the engine 11 and the second discharge amount calculated based on the control pressure detected by the control pressure sensor 19 is obtained.

[0055] In addition, 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, the boom bottom pressure sensor S7B, the arm rod pressure sensor S8R, the arm bottom pressure sensor S8B, the bucket rod pressure sensor S9R, and the bucket bottom pressure sensor S9B are collectively also referred to as "cylinder pressure sensors". Further, a left turning pressure sensor S10L and a right turning pressure sensor S10R are attached to the slewing hydraulic motor 2A.

[0056] The boom rod pressure sensor S7R detects the pressure in the rod-side oil chamber of the boom cylinder 7 (hereinafter referred to as "boom rod pressure"). The boom bottom pressure sensor S7B detects the pressure in the bottom-side oil chamber of the boom cylinder 7 (hereinafter referred to as "boom bottom pressure"). The arm rod pressure sensor S8R detects the pressure in the rod-side oil chamber of the arm cylinder 8 (hereinafter referred to as "arm rod pressure"). The arm bottom pressure sensor S8B detects the pressure in the bottom-side oil chamber of the arm cylinder 8 (hereinafter referred to as "arm bottom pressure"). The bucket rod pressure sensor S9R detects the pressure in the rod-side oil chamber of the bucket cylinder 9 (hereinafter referred to as "bucket rod pressure"). The bucket bottom pressure sensor S9B detects the pressure in the bottom-side oil chamber of the bucket cylinder 9 (hereinafter referred to as "bucket bottom pressure"). The left turning pressure sensor S10L detects the pressure of the hydraulic oil in the left port of the slewing hydraulic motor 2A. The right turning pressure sensor S10R detects the pressure of the hydraulic oil in the right port of the slewing hydraulic motor 2A. The values detected by each sensor are transmitted to the controller 30.

[0057] Next, with reference to FIG. 3, the configuration for the controller 30 to operate the actuator by the machine control function will be described. FIG. 3 is a diagram showing an extracted hydraulic system portion related to the operation of the arm cylinder 8. In FIG. 3, the operation of the arm cylinder 8 is described as an example, but it is not limited thereto. The same applies to the operations of the boom cylinder 7, the bucket cylinder 9, the slewing hydraulic motor 2A, the left travel hydraulic motor 2ML, and the right travel hydraulic motor 2MR, and redundant descriptions will be omitted.

[0058] As shown in FIG. 3, the hydraulic system includes a proportional valve 31. The proportional valve 31 includes a proportional valve 31AL and a proportional valve 31AR.

[0059] The proportional valve 31 functions as a control valve for machine control. The proportional valve 31 is arranged in a pipeline connecting the pilot pump 15 and the pilot port of the corresponding control valve in the control valve unit 17, and is configured to be able to change the flow passage area of the pipeline. In the present embodiment, the proportional valve 31 operates according to a control command output by the controller 30. Therefore, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the pilot port of the corresponding control valve in the control valve unit 17 via the proportional valve 31, regardless of the operation of the operating device 26 by the operator. And the controller 30 can make the pilot pressure generated by the proportional valve 31 act on the pilot port of the corresponding control valve.

[0060] With this configuration, the controller 30 can operate the hydraulic actuator corresponding to the specific operating device 26 even when no operation on the specific operating device 26 is performed. Also, the controller 30 can forcibly stop the operation of the hydraulic actuator corresponding to the specific operating device 26 even when an operation on the specific operating device 26 is being performed.

[0061] For example, as shown in FIG. 3, the left operation lever 26L is used to operate the arm 5. Specifically, the left operation lever 26L utilizes the hydraulic oil discharged by the pilot pump 15 and makes a pilot pressure corresponding to the operation in the front-rear direction act on the pilot port of the control valve 176. More specifically, when the left operation lever 26L is operated in the arm closing direction (rear direction), a pilot pressure corresponding to the operation amount acts on the right pilot port of the control valve 176L and the left pilot port of the control valve 176R. Also, when the left operation lever 26L is operated in the arm opening direction (front direction), a pilot pressure corresponding to the operation amount acts on the left pilot port of the control valve 176L and the right pilot port of the control valve 176R.

[0062] The left operation lever 26L is provided with a switch NS. In this embodiment, the switch NS is a push button switch provided at the tip of the left operation lever 26L. The operator can operate the left operation lever 26L while pressing the switch NS. The switch NS may be provided on the right operation lever 26R, or may be provided at other positions within the cabin 10.

[0063] The operation sensor 29LA detects the content of the forward and backward operation of the left operation lever 26L by the operator, and outputs the detected value to the controller 30.

[0064] The proportional valve 31AL operates in response to a control command (current command) output by the controller 30. Then, it adjusts the pilot pressure by the hydraulic oil introduced from the pilot pump 15 to the right pilot port of the control valve 176L and the left pilot port of the control valve 176R via the proportional valve 31AL. The proportional valve 31AR operates in response to a control command (current command) output by the controller 30. Then, it adjusts the pilot pressure by the hydraulic oil introduced from the pilot pump 15 to the left pilot port of the control valve 176L and the right pilot port of the control valve 176R via the proportional valve 31AR. The proportional valve 31AL can adjust the pilot pressure so that the control valves 176L and 176R can be stopped at arbitrary valve positions. Similarly, the proportional valve 31AR can adjust the pilot pressure so that the control valves 176L and 176R can be stopped at arbitrary valve positions.

[0065] Also, a pilot pressure sensor 32AL for detecting the pilot pressure is provided in the pilot line connecting the proportional valve 31AL and one port of the control valve 176 (the right port of the control valve 176L and the left port of the control valve 176R). Also, a pilot pressure sensor 32AR for detecting the pilot pressure is provided in the pilot line connecting the proportional valve 31AR and the other port of the control valve 176 (the left port of the control valve 176L and the right port of the control valve 176R). The values detected by the respective pilot pressure sensors 32AL, 32AR are transmitted to the controller 30.

[0066] With this configuration, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the right pilot port of the control valve 176L and the left pilot port of the control valve 176R via the proportional valve 31AL in response to the arm closing operation by the operator. Also, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the right pilot port of the control valve 176L and the left pilot port of the control valve 176R via the proportional valve 31AL regardless of the arm closing operation by the operator. That is, the controller 30 can close the arm 5 in response to the arm closing operation by the operator or regardless of the arm closing operation by the operator.

[0067] Also, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the left pilot port of the control valve 176L and the right pilot port of the control valve 176R via the proportional valve 31AR in response to the arm opening operation by the operator. Also, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the left pilot port of the control valve 176L and the right pilot port of the control valve 176R via the proportional valve 31AR regardless of the arm opening operation by the operator. That is, the controller 30 can open the arm 5 in response to the arm opening operation by the operator or regardless of the arm opening operation by the operator.

[0068] Also, with this configuration, even when the arm closing operation by the operator is being performed, the controller 30 can, if necessary, reduce the pilot pressure acting on the closing side pilot ports of the control valve 176 (the left pilot port of the control valve 176L and the right pilot port of the control valve 176R) and forcibly stop the closing operation of the arm 5. The same applies when forcibly stopping the opening operation of the arm 5 when the arm opening operation by the operator is being performed.

[0069] Alternatively, even when the operator performs an arm closing operation, the controller 30 may, if necessary, control the proportional valve 31AR to increase the pilot pressure acting on the opening pilot ports of the control valve 176 (the right pilot port of the control valve 176L and the left pilot port of the control valve 176R) on the side opposite to the closing pilot port of the control valve 176, and force the control valve 176 back to the neutral position, thereby forcibly stopping the closing operation of the arm 5. The same applies when forcibly stopping the opening operation of the arm 5 when the operator performs an arm opening operation.

[0070] Also, although the form of the operating device 26 has been described in relation to an electric operating lever, a hydraulic operating lever may be adopted instead of the electric operating lever. In this case, the lever operation amount of the hydraulic operating lever may be detected in the form of pressure by a pressure sensor and input to the controller 30. Also, a solenoid valve may be arranged between the operating device 26 as a hydraulic operating lever and the pilot ports of each control valve. The solenoid valve is configured to operate in response to an electric signal from the controller 30. With this configuration, when a manual operation is performed using the operating device 26 as a hydraulic operating lever, the operating device 26 can move each control valve by increasing or decreasing the pilot pressure according to the lever operation amount. Also, 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 operating lever.

[0071] Next, an example will be described in which the operator operates the left operation lever 26L of the operation device 26 to operate the arm cylinder 8. When the operator operates the left operation lever 26L of the operation device 26, the operation of the left operation lever 26L is detected by the operation sensor 29LA, and the detected operation of the left operation lever 26L is input to the controller 30. The controller 30 controls and outputs the current value (current command, control command) of the proportional valve 31 so as to be the secondary pressure (pilot pressure) of the control valve 176 corresponding to the operation amount of the left operation lever 26L. As a result, the pilot pressure acts on the pilot port of the control valve 176, and the spool of the control valve 176 moves, so that the opening areas of the PT opening (opening of the oil passage from the main pump 14 to the hydraulic oil tank), the PC opening (opening of the oil passage from the main pump 14 to the arm cylinder 8), and the CT opening (opening of the oil passage from the arm cylinder 8 to the hydraulic oil tank) of the control valve 176 are controlled.

[0072] Here, when the left operation lever 26L is operated from the neutral position in the tilting direction to operate the arm cylinder 8, the opening area of the PT opening of the control valve 176 decreases, and the pump pressure (pressure of the discharge pressure sensor 28) of the main pump 14 increases. Further, when the left operation lever 26L is operated, the opening area of the PT opening of the control valve 176 further decreases, and the opening areas of the PC opening and the CT opening of the control valve 176 increase.

[0073] When the pump pressure becomes higher than the load pressure, the load check valve is pushed open, and hydraulic oil is supplied from the main pump 14 through the PC opening of the control valve 176 to one chamber (for example, the bottom side oil chamber) of the arm cylinder 8. At the same time, as the control pressure (also referred to as negative control pressure) detected by the control pressure sensor 19 decreases, the regulator 13 controls to increase the discharge amount of the main pump 14. Then, as the load pressure acts on the arm cylinder 8, the arm cylinder 8 operates, and the hydraulic oil flowing out from the other chamber (for example, the rod side oil chamber) of the arm cylinder 8 returns to the hydraulic oil tank through the CT opening of the control valve 176.

[0074] Here, with reference to FIG. 4, the relationship between the operation amount of the operation device 26 (left operation lever 26L, right operation lever 26R, traveling lever 26D) and the secondary pressure supplied to the control valve 176 that controls the flow rate of the hydraulic oil flowing through the hydraulic actuators (boom cylinder 7, arm cylinder 8, bucket cylinder 9, left traveling hydraulic motor 2ML, right traveling hydraulic motor 2MR, and slewing hydraulic motor 2A) will be described. In the following description, the relationship between the forward and backward lever operation amount (lever angle tilted from the neutral position) of the left operation lever 26L and the secondary pressure supplied to the control valve 176 will be described as an example. The relationship between the operation amounts of the other operation devices 26 and the secondary pressures supplied to the respective control valves is the same, and redundant descriptions will be omitted.

[0075] FIG. 4 is a graph showing the relationship between the lever operation amount and the commanded secondary pressure of the control valve 176. In FIG. 4, the horizontal axis represents the operation amount of the left operation lever 26L detected by the operation sensor 29LA and input to the controller 30. The vertical axis represents the commanded secondary pressure, which is the secondary pressure (pilot pressure) of the control valve 176 determined based on the lever operation amount.

[0076] Also, in FIG. 4, the operation amount LS_0 indicates a state where the left operation lever 26L is in the neutral position. The operation amount LS_F indicates a state where the left operation lever 26L is operated at the maximum operation amount. FIG. 4 shows the relationship between the lever operation amount and the commanded secondary pressure when the left operation lever 26L is operated in one direction (for example, the forward direction). The relationship between the lever operation amount and the commanded secondary pressure when the left operation lever 26L is operated in the other direction (for example, the backward direction) is the same, and redundant descriptions will be omitted.

[0077] As shown in FIG. 4, between the lever operation amount of the left operation lever 26L from the operation amount LS_0 to the operation amount LS_1, it is the dead zone of the left operation lever 26L, and the commanded secondary pressure of the control valve 176 remains 0.

[0078] When the lever operation amount of the left operation lever 26L is operated beyond the dead zone and is between the operation amount LS_1 and the operation amount LS_2, the commanded secondary pressure increases from the pressure D1 to the pressure D2 in proportion to the increase in the lever operation amount.

[0079] When the lever operation amount of the left operation lever 26L is operated beyond the operation amount LS_2, the command secondary pressure of the control valve 176 rapidly rises from the pressure D2 to the pressure D3. Between the operation amount LS_2 and the operation amount LS_F, the command secondary pressure remains constant at the pressure D3.

[0080] Here, the pressure D2 is, for example, a specified value (theoretical value) for maximizing the spool stroke of the control valve 176. However, due to errors in the characteristics of the control valve 176 (for example, mechanical errors based on tolerances of the spring that biases the spool of the control valve 176 to the neutral position, etc.), errors in the characteristics of the proportional valve 31 (mechanical errors), errors in the operating device 26 (mechanical errors), etc., there is a possibility that the spool of the control valve 176 may not reach the full stroke even when the command secondary pressure is set to the pressure D2.

[0081] Therefore, when the lever operation amount of the left operation lever 26L is operated beyond the operation amount LS_2, the command secondary pressure of the control valve 176 is set to a pressure D3 that is sufficiently greater than the pressure D2. In the following description, the region where the lever operation amount of the left operation lever 26L is operated beyond the operation amount LS_2 and the command secondary pressure of the control valve 176 is greater than the pressure D2 is also referred to as the short region ST. Thereby, even if there are errors (mechanical errors) in the control valve 176 or the like, the spool of the control valve 176 can be surely set to the full stroke. Also, in the region ST, the PC opening of the control valve 176 and the CT opening of the control valve 176 can be set to the maximum openings respectively, and the operating speed of the arm cylinder 8 can be set to the maximum speed in design.

[0082] Next, the relationship between the command secondary pressure of the control valve 176 determined by the controller 30 based on the lever operation amount of the left operation lever 26L and the control secondary pressure of the control valve 176 controlled by the controller 30 via the proportional valve 31 will be described with reference to FIG. 5. FIG. 5 is an example of a graph showing the relationship between the command secondary pressure 501 and the control secondary pressure 502 in the reference example. In FIG. 5, the horizontal axis indicates time. The vertical axis indicates the pressures of the command secondary pressure 501 and the control secondary pressure 502.

[0083] Based on the command secondary pressure 501 of the control valve 176 according to the lever operation amount detected by the operation sensor 29LA, the controller 30 performs lag control, and controls the current value (current command, control command) of the proportional valve 31 based on the controlled secondary pressure 502 of the control valve 176 after the lag control. As a result, as the opening area of the control valve 176 gradually expands, the cylinder speed of the arm cylinder 8 can also be smoothly increased, and the operability of the excavator 100 is improved.

[0084] The lag control may be, for example, a first-order lag process. Also, the lag control is not limited to the first-order lag process. For example, it may be a process (control) that limits the acceleration rate of the opening area, or it may be a second-order lag or the like.

[0085] Here, the operator operates the left operation lever 26L from the neutral position (operation amount LS_0 shown in FIG. 4) to the full stroke (operation amount LS_F shown in FIG. 4).

[0086] As shown in FIG. 5, the command secondary pressure 501 indicated by the solid line increases in proportion to the increase in the lever operation amount until it reaches the pressure D2 (see reference numeral 501a). When the lever operation amount reaches the operation amount LS_2 (see FIG. 4) and the command secondary pressure 501 reaches the pressure D2 (see reference numeral 501b), the command secondary pressure 501 rapidly rises to the pressure D3 (see reference numeral 501c), and then becomes constant at the pressure D3 (see reference numeral 501d).

[0087] The controlled secondary pressure 502 indicated by the broken line first increases in proportion to the increase in the lever operation amount (see reference numeral 502a). Then, from a point in time (see reference numeral 502b) that is later than the point in time when the command secondary pressure 501 reaches the pressure D2 (see reference numeral 501b), the controlled secondary pressure 502 rapidly rises (see reference numeral 502c).

[0088] Thus, at the time indicated by reference numeral 502b, the control secondary pressure 502 is lower than the pressure D2. In other words, at the time indicated by reference numeral 502b, the spool of the control valve 176 is before reaching the full stroke. Therefore, between the time indicated by reference numeral 502b and the time when the spool of the control valve 176 reaches the full stroke, the control secondary pressure 502 rapidly increases, causing the operation of the hydraulic actuator (arm cylinder 8) to change suddenly and the operability of the excavator 100 to deteriorate.

[0089] Therefore, it is preferable that the control secondary pressure after the time indicated by reference numeral 502b rises smoothly like the control secondary pressure indicated by the dashed-dotted line (see reference numeral 503c). This suppresses sudden changes in the operation of the hydraulic actuator (arm cylinder 8) and improves the operability of the excavator 100.

[0090] Note that when delay control is not performed, at the time when the command secondary pressure 501 reaches the pressure D2 (see reference numeral 501b), the spool of the control valve 176 is approximately at the full stroke. Therefore, even if the command secondary pressure 501 rapidly increases (see reference numeral 501c), the spool stroke of the control valve 176 hardly changes, and it is difficult for the operator to sense sudden changes in the operation of the hydraulic actuator (arm cylinder 8).

[0091] However, it is also conceivable that at the time when the command secondary pressure 501 reaches the pressure D2 (see reference numeral 501b), the spool of the control valve 176 does not reach the full stroke due to the differential of the control valve 176 or the like. In this case, even when delay control is not performed, between the time when the spool of the control valve 176 reaches the full stroke, the command secondary pressure 501 rapidly increases, causing the operation of the hydraulic actuator (arm cylinder 8) to change suddenly and there is a possibility that the operability of the excavator 100 deteriorates.

[0092] <Control Method of Excavator According to the First Embodiment> Next, a control method for the excavator 100 according to the first embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a flowchart for explaining the control method of the excavator 100 according to the first embodiment. FIG. 7 is a graph showing the relationship between the lever operation amount and the command secondary pressure of the control valve in the excavator 100 according to the first embodiment.

[0093] In step S101, the controller 30 determines whether it is equal to or greater than the short region ST. Here, the controller 30 determines that it is equal to or greater than the short region ST when the lever operation amount is equal to or greater than a predetermined operation amount, and determines that it is not equal to or greater than the short region ST when the lever operation amount is less than the predetermined operation amount. Here, the predetermined operation amount is the full stroke of the lever operation amount (operation amount LS_F in FIG. 7) or the operation amount immediately before the full stroke (for example, 95% or more of the full stroke) (operation amount LS_2 in FIG. 7). When the predetermined operation amount is the full stroke, the relationship between the lever operation amount and the command secondary pressure shown in FIG. 7 is that the command secondary pressure rapidly rises from pressure D2 to pressure D3 at the full stroke.

[0094] In the following description, the case where the predetermined operation amount is the operation amount LS_2 will be described as an example. In this case, when the command secondary pressure is equal to or greater than pressure D2 (see FIG. 7 and FIG. 8 described later), it is determined that it is equal to or greater than the short region ST.

[0095] If it is not equal to or greater than the short region ST in the determination of step S101 (S101·NO), the process of the controller 30 proceeds to step S102.

[0096] In step S102, the controller 30 outputs a pressure corresponding to the lever characteristics.

[0097] In step S102, the controller 30 determines the commanded secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA and the relationship between the lever operation amount shown in FIG. 7 and the commanded secondary pressure of the control valve. Note that when it is not above the short region ST (the region where the commanded secondary pressure is below pressure D2, the region where the lever operation amount is below operation amount LS_2), the lever operation amount and the commanded secondary pressure are uniquely determined by the relationship shown in FIG. 7. Then, the controller 30 performs lag control on the determined commanded secondary pressure to calculate the controlled secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated controlled secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0098] Note that in a configuration where lag control is not performed, in step S102, the controller 30 determines the commanded secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA and the relationship between the lever operation amount shown in FIG. 7 and the commanded secondary pressure of the control valve. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the determined commanded secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0099] On the other hand, in the determination of step S101, if it is above the short region ST (S101·YES), the process of the controller 30 proceeds to step S103.

[0100] In step S103, the controller 30 determines whether the commanded secondary pressure is equal to or higher than the maximum pressure D3. Here, in the region 701 shown in FIG. 7 (the region where the lever operation amount is equal to or greater than operation amount LS_2 and equal to or less than operation amount LS_F), when first reaching the region 701, the commanded secondary pressure becomes pressure D2. Then, the commanded secondary pressure is added in a fixed amount (see step S104 described later). The determination is made based on the commanded secondary pressure obtained in this way.

[0101] In the determination of step S103, if the commanded secondary pressure is not equal to or higher than the maximum pressure D3 (S103·NO), the process of the controller 30 proceeds to step S104.

[0102] In step S104, the controller 30 performs control to increase the pilot pressure (secondary pressure) of the control valve 176 by a certain amount at a time.

[0103] Here, control is performed so that the commanded secondary pressure rises slowly. That is, when the lever operation amount is equal to or greater than the operation amount LS_2 (see FIG. 7), the controller 30 increases the commanded secondary pressure by a certain amount per unit time. In other words, when the lever operation amount is equal to or greater than the operation amount LS_2, the controller 30 determines the commanded secondary pressure of the control valve 176 based on the time during which the lever operation amount is equal to or greater than the operation amount LS_2. Then, the controller 30 performs delay control on the determined commanded secondary pressure to calculate the controlled secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated controlled secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0104] Note that in a configuration where delay control is not performed, in step S104, the controller 30 increases the commanded secondary pressure by a certain amount per unit time. In other words, the controller 30 determines the commanded secondary pressure of the control valve 176 based on the time during which the lever operation amount is equal to or greater than the operation amount LS_2. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the determined commanded secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0105] In this way, by the process of step S104, the commanded secondary pressure rises by a certain amount, and the commanded secondary pressure reaches the maximum pressure D3.

[0106] In the determination of step S103, if the commanded secondary pressure is equal to or higher than the maximum pressure D3 (S103·YES), the process of the controller 30 proceeds to step S105.

[0107] In step S105, the controller 30 outputs the maximum pressure D3. That is, the controller 30 determines the commanded secondary pressure to be the maximum pressure D3. Then, the controller 30 performs lag control on the determined commanded secondary pressure to calculate the controlled secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated controlled secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0108] Note that in a configuration where lag control is not performed, in step S105, the controller 30 determines the commanded secondary pressure to be the maximum pressure D3. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the determined commanded secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0109] Next, the commanded secondary pressure and the controlled secondary pressure controlled by the control method shown in FIG. 6 will be described with reference to FIG. 8. FIG. 8 is an example of a graph showing the relationship between the commanded secondary pressure 511 and the controlled secondary pressure 512 in the first embodiment. In FIG. 8, the horizontal axis represents time. The vertical axis represents the pressures of the commanded secondary pressure 511 and the controlled secondary pressure 512.

[0110] Here, the operator operates the left operation lever 26L from the neutral position (operation amount LS_0 shown in FIG. 4) to the full stroke (operation amount LS_F shown in FIG. 4).

[0111] As shown in FIG. 8, the commanded secondary pressure 511 indicated by the solid line increases in proportion to the increase in the lever operation amount until it reaches the pressure D2 (see reference numeral 511a). That is, the commanded secondary pressure 511 is determined by the process shown in step S102.

[0112] Then, when the lever operation amount reaches the operation amount LS_2 (see FIG. 4) and the commanded secondary pressure 511 reaches the pressure D2 (see reference sign 511b), the commanded secondary pressure 511 increases by a certain amount per unit time (see reference sign 511c). That is, the commanded secondary pressure 511 is determined by the process shown in step S104.

[0113] Furthermore, when the commanded secondary pressure 511 reaches the pressure D3, it then becomes constant at the maximum pressure D3 (omitted in FIG. 8). That is, the commanded secondary pressure 511 is determined by the process shown in step S105.

[0114] By determining the commanded secondary pressure 511 as described above, the controlled secondary pressure 512 shown by the dashed line first increases in proportion to the increase in the lever operation amount (see reference sign 512a). Then, from a point in time (see reference sign 512b) that is later than the point in time when the commanded secondary pressure 511 reaches the pressure D2 (see reference sign 511b), the controlled secondary pressure 512 rises gently compared to the case of FIG. 5 (see reference sign 512c).

[0115] Thus, at the point in time indicated by reference sign 512b, the controlled secondary pressure 512 has a value lower than the pressure D2. In other words, at the point in time indicated by reference sign 512b, the spool of the control valve 176 is before full stroke. Here, according to the control according to the first embodiment, from the point in time indicated by reference sign 512b until the spool of the control valve 176 reaches full stroke, the controlled secondary pressure 512 rises gently, suppressing a sudden change in the operation of the hydraulic actuator (arm cylinder 8) and improving the operability of the excavator 100.

[0116] Note that even when delay control is not performed, until the spool of the control valve 176 reaches full stroke, the commanded secondary pressure 511 rises gently, suppressing a sudden change in the operation of the hydraulic actuator (arm cylinder 8) and improving the operability of the excavator 100.

[0117] As described above, the controller 30 has a first operation area and a second operation area (area ST). The first operation area is a case where the lever operation amount is less than the operation amount LS_2 (see FIG. 4), and determines the commanded secondary pressure based on the lever operation amount. The second operation area is a case where the lever operation amount is greater than or equal to the operation amount LS_2 (see FIG. 4), and limits the increase amount of the commanded secondary pressure to determine the commanded secondary pressure. Specifically, in the second operation area, the commanded secondary pressure is increased by a certain amount per unit time. Also, in the second operation area, when the commanded secondary pressure is greater than or equal to the maximum pressure D3, the commanded secondary pressure is determined as the maximum pressure D3. Thereby, a sudden change in the operation of the hydraulic actuator (arm cylinder 8) is suppressed, and the operability of the excavator 100 is improved.

[0118] Also, by setting the commanded secondary pressure to the maximum pressure D3, even if there is an error (mechanical error) in the control valve 176 or the like, the spool of the control valve 176 can be surely fully stroked. Also, in the area ST, the PC opening of the control valve 176 and the CT opening of the control valve 176 can be set to the maximum openings, and the operation speed of the arm cylinder 8 can be set to the maximum speed in design.

[0119] Note that in step S104, it has been described that the commanded secondary pressure is controlled to increase slowly, but it is not limited thereto. The control secondary pressure may be controlled to increase slowly. That is, when the lever operation amount is greater than or equal to the operation amount LS_2 (see FIG. 4), the increase amount of the control secondary pressure per unit time is limited.

[0120] The controller 30 determines the commanded secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA and the relationship between the lever operation amount shown in FIG. 4 and the commanded secondary pressure of the control valve. Then, the controller 30 performs lag control on the determined commanded secondary pressure to calculate the controlled secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated controlled secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31. Thereby, a sudden change in the operation of the hydraulic actuator (arm cylinder 8) is suppressed, and the operability of the excavator 100 is improved.

[0121] <Control Method of Excavator According to Second Embodiment> Next, the control method of the excavator 100 according to the second embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart for explaining the control method of the excavator 100 according to the second embodiment. FIG. 10 is a graph showing the relationship between the lever operation amount and the commanded secondary pressure of the control valve in the excavator 100 according to the second embodiment.

[0122] In step S201, the controller 30 determines whether the controlled secondary pressure is equal to or higher than the short region ST. Here, the controller 30 determines whether the controlled secondary pressure is equal to or higher than a predetermined threshold pressure (pressure D2).

[0123] Specifically, the controller 30 performs lag control on the commanded secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA, and calculates the controlled secondary pressure of the control valve 176 after the lag control. The controller 30 determines whether the calculated controlled secondary pressure is equal to or higher than a predetermined threshold pressure (pressure D2).

[0124] Further, the controller 30 may determine whether the pilot pressure acting on the pilot port of the control valve 176 (the actual pressure of the pilot pressure detected by the pilot pressure sensor 32, the actual controlled secondary pressure) is equal to or higher than a predetermined threshold pressure (pressure D2).

[0125] Further, the controller 30 may determine whether or not the command secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA is equal to or higher than a predetermined threshold pressure (a pressure that is large enough to be regarded as the control secondary pressure being equal to or higher than the pressure D2).

[0126] In the determination of step S201, when the control secondary pressure is equal to or higher than the short region ST (S201·YES), the process of the controller 30 proceeds to step S202.

[0127] In step S202, the controller 30 maximizes the command secondary pressure. That is, the controller 30 determines the command secondary pressure as the maximum pressure D3. Then, the controller 30 performs lag control on the determined command secondary pressure to calculate the control secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated control secondary pressure and the characteristics of the proportional valve 31 (the relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0128] On the other hand, in the determination of step S201, when the control secondary pressure is not equal to or higher than the short region ST (S201·NO), the process of the controller 30 proceeds to step S203.

[0129] In step S203, the controller 30 outputs a pressure corresponding to the electric lever characteristics.

[0130] In step S203, the controller 30 determines the commanded secondary pressure of the control valve 176 based on the lever operation amount detected by the operation sensor 29LA and the relationship between the lever operation amount shown in FIG. 10 and the commanded secondary pressure of the control valve. Note that when the controlled secondary pressure is not greater than or equal to the short region ST, the lever operation amount and the commanded secondary pressure are uniquely determined by the relationship shown in FIG. 10. Then, the controller 30 performs lag control on the determined commanded secondary pressure to calculate the controlled secondary pressure. Then, the controller 30 determines the current value (current command, control command) of the proportional valve 31 based on the calculated controlled secondary pressure and the characteristics of the proportional valve 31 (relationship between the current value and the secondary pressure). Then, the controller 30 supplies the determined current value (current command, control command) to the proportional valve 31.

[0131] Also, in step S201, the controller 30 may determine whether the lever operation amount detected by the operation sensor 29LA is equal to or greater than a predetermined threshold operation amount that is large enough to be regarded as the controlled secondary pressure being equal to or greater than the pressure D2. That is, when the lever operation amount is equal to or greater than the predetermined threshold operation amount (S201·YES), the commanded secondary pressure may be rapidly increased to the maximum (S202).

[0132] Next, the commanded secondary pressure and the controlled secondary pressure controlled by the control method shown in FIG. 9 will be described with reference to FIG. 11. FIG. 11 is an example of a graph showing the relationship between the commanded secondary pressure 521 and the controlled secondary pressure 522 in the second embodiment. In FIG. 11, the horizontal axis represents time. The vertical axis represents the pressures of the commanded secondary pressure 521 and the controlled secondary pressure 522.

[0133] Here, the operator operates the left operation lever 26L from the neutral position (operation amount LS_0 shown in FIG. 10) to the full stroke (operation amount LS_F shown in FIG. 10).

[0134] As shown in FIG. 11, the commanded secondary pressure 521 indicated by the solid line increases in proportion to the increase in the lever operation amount until it reaches the pressure D2 (see reference sign 521a). And even when the lever operation amount reaches the operation amount LS_2 (see FIG. 10), until the control secondary pressure 522 reaches the pressure D2, the commanded secondary pressure 521 indicated by the solid line increases in proportion to the increase in the lever operation amount (see reference sign 521a). That is, the commanded secondary pressure 521 is determined by the process shown in step S203.

[0135] And when the control secondary pressure 522 indicated by the broken line reaches the pressure D2 (see reference sign 522b), the commanded secondary pressure 521 rapidly increases to the maximum pressure D3 (see reference sign 521b), and then becomes constant at the maximum pressure D3 (see reference sign 521c). That is, the commanded secondary pressure 521 is determined by the process shown in step S202.

[0136] By determining the commanded secondary pressure 521 as described above, the control secondary pressure 522 indicated by the broken line first increases in proportion to the increase in the lever operation amount (see reference sign 522a). And when the control secondary pressure 522 reaches the pressure D2 (see reference sign 522b), the commanded secondary pressure 521 rapidly rises to the maximum pressure D3, so that the control secondary pressure 522 also rapidly rises (see reference sign 522c). However, at this time, the PC opening and the CT opening of the control valve 176 are in a fully open state, and even if the control secondary pressure 522 rapidly rises, a sudden change in the operation of the hydraulic actuator (arm cylinder 8) is suppressed, and the operability of the excavator 100 is improved.

[0137] Also, by setting the commanded secondary pressure to the maximum pressure D3, even if there is an error (mechanical error) in the control valve 176 or the like, the spool of the control valve 176 can be surely set to the full stroke. Further, in the region ST, the PC opening of the control valve 176 and the CT opening of the control valve 176 can be made the maximum openings respectively, and the operating speed of the arm cylinder 8 can be made the maximum speed in design.

[0138] Although the excavator 100 has been described above as an example of a working machine, the configuration of the working machine is not limited to this. Although an example of a working machine (excavator 100) has been described in which an operator boards the cabin 10 and the operator operates the operating device 26 provided in the cabin 10, the configuration of the working machine (excavator 100) is not limited to this. The working machine (excavator 100) may be configured to be remotely operable from the outside.

[0139] For example, an excavator system includes a remote operation room and a working machine (excavator 100). The remote operation room includes a seat on which an operator sits, an operating device operated by the operator sitting on the seat, a display device, and a remote operation room control unit. The remote operation room control unit is communicably connected to the controller 30 of the working machine (excavator 100). For example, an image captured by the imaging device S6 of the working machine (excavator 100) is displayed on the display device. The operating device is configured to be able to receive an operator's operation in the same manner as the operating device 26. The operation amount is input to the remote operation room control unit by an operation sensor provided in the operating device. The remote operation room control unit transmits the operation amount to the controller 30 via a communication line and the communication device T1 of the excavator. The controller 30 controls the operation of each actuator of the excavator 100 based on the operation amount of the operating device transmitted from the remote operation room control unit instead of the detection value of the operation sensor 29.

[0140] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The above embodiments may be omitted, replaced, or changed in various forms without departing from the scope and spirit of the appended claims.

Description of Reference Numerals

[0141] 1 Lower Travel Body 1L, 1R Travel Hydraulic Motors (Hydraulic Actuators) 2 Swing Mechanism 2A Swing Hydraulic Motor (Hydraulic Actuator) 2ML Left Travel Hydraulic Motor (Hydraulic Actuator) 2MR Right Travel Hydraulic Motor (Hydraulic Actuator) 3 Upper Swing Body 4 Boom 5 Arm 6 Bucket 7 Boom Cylinder (Hydraulic Actuator) 8 Arm Cylinder (Hydraulic Actuator) 9 Bucket Cylinder (Hydraulic Actuator) 13 Regulator 14 Main Pump (Hydraulic Pump) 15 Pilot Pump 17 Control Valve Unit 171~176 Control Valves 18 Throttle 19 Control Pressure Sensor 26 Operating Device 26R Right Operating Lever 26L Left Operating Lever 30 Controller 31 Proportional Valve (Electromagnetic Proportional Valve) 100 Excavator 501,511,521 Command Secondary Pressure 502,512,522 Control Secondary Pressure

Claims

1. A hydraulic actuator, a hydraulic pump, a control valve for controlling the flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator, an electromagnetic proportional valve for controlling the secondary pressure input to the control valve, a controller to which the operation amount of an operation lever is input and which controls the electromagnetic proportional valve, and comprising: The controller, when the input operation amount of the operation lever is less than a predetermined operation amount, determines a commanded secondary pressure based on the operation amount of the operation lever, when the input operation amount of the operation lever is greater than or equal to the predetermined operation amount, limits the increase amount of the commanded secondary pressure and determines the commanded secondary pressure, controls the current value of the electromagnetic proportional valve based on the commanded secondary pressure, An excavator.

2. The predetermined operation amount is immediately before the full stroke of the operation lever or is the full stroke, The excavator according to Claim 1.

3. The excavator according to Claim 2, wherein immediately before the full stroke is 95% or more of the full stroke of the operation lever.

4. The controller, when the operation amount of the operation lever is greater than or equal to a predetermined operation amount, determines whether the commanded secondary pressure is greater than or equal to the maximum pressure, when the commanded secondary pressure is greater than or equal to the maximum pressure, determines the commanded secondary pressure to be the maximum pressure, when the commanded secondary pressure is less than the maximum pressure, limits the increase amount of the commanded secondary pressure and determines the commanded secondary pressure, The excavator according to Claim 1.

5. The controller, when the operation amount of the operation lever is greater than or equal to a predetermined operation amount and the commanded secondary pressure is less than the maximum pressure, increases the commanded secondary pressure by a constant amount per unit time, The excavator according to Claim 4.

6. The controller, performs delay control on the commanded secondary pressure, calculates a controlled secondary pressure subjected to delay control, controls the current value of the electromagnetic proportional valve based on the controlled secondary pressure, The excavator according to any one of Claims 1 to 5.

7. A hydraulic actuator, a hydraulic pump, a control valve for controlling the flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator, an electromagnetic proportional valve for controlling the secondary pressure input to the control valve, a controller to which the operation amount of an operation lever is input and which controls the electromagnetic proportional valve, and comprising: The controller, performs delay control on the commanded secondary pressure, calculates a controlled secondary pressure subjected to delay control, controls the current value of the electromagnetic proportional valve based on the controlled secondary pressure, The controller is configured to: when the control secondary pressure is less than a predetermined threshold value, determine the commanded secondary pressure based on the operation amount of the operation lever; when the control secondary pressure is greater than or equal to the predetermined threshold value, rapidly increase the commanded secondary pressure; an excavator.

8. The determination as to whether the control secondary pressure is less than the predetermined threshold value is made based on any one of the commanded secondary pressure, the control secondary pressure, and the actual control secondary pressure input to the control valve. The excavator according to claim 7.

9. When the operation amount of the operation lever is greater than or equal to a predetermined operation amount, rapidly increase the commanded secondary pressure. The excavator according to claim 7.

Images