Shovel

Abstract

To provide a shovel capable of preventing unintended stop of a driving source while reducing the cost.SOLUTION: A shovel includes an undercarriage, a revolving super structure turnable relative to the undercarriage, a driving source 11, a hydraulic pump 14 driven by the driving source, a regulator 13 for controlling a flow rate of working fluid discharged from the hydraulic pump, a hydraulic actuator 9, a directional control valve 174 for controlling the working fluid supplied from the hydraulic pump to the hydraulic actuator, an operation device 26, and a control device 30. The control device includes a failure determination unit for determining failure of the regulator, and a control valve control unit to which an operation amount of the operation device is input and which controls the directional control valve. The control valve control unit controls the directional control valve by driving source stall prevention control when the failure determination unit determines the failure of the regulator.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a shovel. [Background technology]

[0002] Patent Document 1 discloses an excavator equipped with a regulator, a controller, an electromagnetic proportional valve, a redundant electromagnetic switching valve, a pilot type hydraulic proportional valve, and a pilot hydraulic pump, and equipped with a discharge amount control circuit that controls the pump discharge amount of a variable displacement hydraulic pump. According to Patent Document 1, when a malfunction occurs in the electrical system, secondary pressure from the pilot type hydraulic proportional valve is applied to the control side piston of the regulator via the redundant electromagnetic switching valve, thereby controlling the discharge amount of the hydraulic pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-256814 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the excavator disclosed in Patent Document 1 is provided with a redundant solenoid-operated switching valve and a pilot-operated hydraulic proportional valve as redundant devices in a control system of a regulator using an electromagnetic proportional valve, which poses a problem of increased cost of the excavator.

[0005] In view of the above problems, an object of the present invention is to provide a shovel that prevents unintended stopping of the drive source while reducing costs. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, an excavator according to an embodiment of the present invention comprises a lower running body, an upper rotating body capable of rotating relative to the lower running body, a drive source, a hydraulic pump driven by the drive source, a regulator controlling a flow rate of hydraulic oil discharged by the hydraulic pump, a hydraulic actuator, a directional control valve controlling the hydraulic oil supplied from the hydraulic pump to the hydraulic actuator, an operation device, and a control device, wherein the control device has a failure determination unit that determines a failure of the regulator, and a control valve control unit that receives an operation amount of the operation device and controls the directional control valve, and when the failure determination unit determines that the regulator has failed, the control valve control unit controls the directional control valve by drive source stall prevention control. Effect of the Invention

[0007] According to the above-described embodiment, it is possible to provide a shovel that prevents unintended stopping of the drive source while reducing costs. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] FIG. 2 is a diagram showing a configuration example of a hydraulic system mounted on a shovel. [Diagram 3] FIG. 2 is a diagram showing the configuration of a pump discharge amount control circuit. [Figure 4] FIG. 2 is a diagram illustrating a hydraulic system portion related to the operation of a boom cylinder. [Diagram 5] 4 is a graph showing the relationship between pump pressure, pump flow rate, and torque. [Figure 6] 4 is a flowchart showing a first engine stall prevention control for a shovel. [Figure 7] 6 is a flowchart showing a second engine stall prevention control of the excavator. [Figure 8] 13 is a flowchart showing a third engine stall prevention control of the excavator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] In this embodiment, the lower traveling structure 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 structure 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 (see FIG. 2 described later).

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

[0012] A boom 4 is attached to the upper rotating body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5 as an end attachment. The boom 4, arm 5, and 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, arm cylinder 8, and bucket cylinder 9 constitute an attachment actuator. In the example shown in FIG. 1, the bucket 6 is an excavation bucket, but may be a skeleton bucket or a gravel removal bucket. The bucket 6 may also be equipped with a bucket tilt mechanism.

[0013] The upper rotating body 3 is provided with a cabin 10 as a driver's cab, and is equipped with a drive source such as an engine 11. An operation device 26 (see FIG. 2 described later), a controller 30, etc. are provided inside the cabin 10. In addition, a spatial recognition device 70, etc. are attached to the upper rotating body 3. For convenience, in this specification, the side of the upper rotating body 3 to which an attachment AT is attached is referred to as the front, and the side to which a counterweight is attached is referred to as the rear.

[0014] The spatial recognition device 70 is configured to recognize an object present in a three-dimensional space around the shovel 100. The spatial recognition device 70 may be configured to calculate a distance from the spatial recognition device 70 or the shovel 100 to the recognized object. The spatial 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, or any combination thereof. The imaging device is, for example, a monocular camera or a stereo camera. In this embodiment, the spatial recognition device 70 includes a forward sensor 70F attached to the front end of the upper surface of the cabin 10, a rear sensor 70B attached to the rear end of the upper surface of the upper rotating body 3, a left sensor 70L attached to the left end of the upper surface of the upper rotating body 3, and a right sensor (not shown) attached to the right end of the upper surface of the upper rotating body 3. An upward sensor (not shown) that recognizes an object present in the space above the upper rotating body 3 may be attached to the shovel 100.

[0015] The operating device 26 is a device used by an operator to operate the 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 (control device) 30 is a control device for controlling the shovel 100. In this embodiment, the controller 30 is configured with a computer including a CPU, a volatile storage device, a nonvolatile storage device, and the like. The controller 30 reads out a program corresponding to each function from the nonvolatile storage device, loads it into the volatile storage device, and causes the CPU to execute the corresponding process. Each function includes, for example, a machine guidance function that guides the operator in manually operating the shovel 100, and a machine control function that supports the operator in manually operating the shovel 100 or automatically or autonomously operates the shovel 100. The controller 30 may include a contact avoidance function that automatically or autonomously operates or stops the shovel 100 to avoid contact between the shovel 100 and an object present within a monitoring range around the shovel 100. Monitoring of objects around the shovel 100 is performed not only within the monitoring range but also outside the monitoring range.

[0017] Next, a configuration example of a hydraulic system mounted on the shovel 100 will be described with reference to Fig. 2. Fig. 2 is a diagram showing a configuration example of a hydraulic system mounted on the shovel 100. In Fig. 2, a mechanical power transmission system, a hydraulic oil line, a pilot line, and an electric control system are indicated by double lines, solid lines, dashed 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, a controller 30, and the like.

[0019] In FIG. 2, the hydraulic system is configured to circulate hydraulic oil from a main pump 14 driven by an engine 11 through a center bypass line 40 or a parallel line 42 to a hydraulic oil tank.

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

[0021] The main pump (hydraulic pump) 14 is configured to supply hydraulic oil via a hydraulic oil line to the control valve unit 17. In this 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 (pump flow rate) of the main pump 14. In this 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 this 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, the main pump 14 may have a function of supplying hydraulic oil to various hydraulic control devices via a pilot line, in addition to a function of supplying hydraulic oil to the control valve unit 17 via a hydraulic oil 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 (directional 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 hydraulic oil discharged by the main pump 14 to one or more hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 control, for example, the flow rate of hydraulic oil flowing from the main pump 14 to the hydraulic actuators and the flow rate of hydraulic oil flowing from the hydraulic actuators to a hydraulic oil tank. The hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left traveling hydraulic motor 2ML, a right traveling hydraulic motor 2MR, and a swing hydraulic motor 2A.

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

[0026] The discharge pressure sensor 28 is configured to be able to detect the discharge pressure (pump 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 detect the content of an operation of the operation device 26 by an operator. In this 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 hydraulic oil to a hydraulic oil tank via a left center bypass line 40L or a left parallel line 42L, and the right main pump 14R circulates hydraulic oil to a hydraulic oil tank via a right center bypass line 40R or a right parallel line 42R.

[0029] The left center bypass line 40L is a hydraulic oil line that passes through control valves 171, 173, 175L, and 176L arranged in the control valve unit 17. The right center bypass line 40R is a hydraulic oil line that passes through 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 traveling hydraulic motor 2ML and to discharge the hydraulic oil discharged by the left traveling 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 traveling hydraulic motor 2MR and to discharge the hydraulic oil discharged by the right traveling 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 by 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 by 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 by 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 by 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 by 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 conduit 42L is a hydraulic oil line that runs parallel to the left center bypass conduit 40L. The left parallel conduit 42L can supply hydraulic oil to a more downstream control valve when the flow of hydraulic oil through the left center bypass conduit 40L is restricted or blocked by any of the control valves 171, 173, and 175L. The right parallel conduit 42R is a hydraulic oil line that runs parallel to the right center bypass conduit 40R. The right parallel conduit 42R can supply hydraulic oil to a more downstream control valve when the flow of hydraulic oil through the right center bypass conduit 40R is restricted or blocked by any 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, 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, for example, to reduce the discharge amount. The same is true for the right regulator 13R. This is to prevent the absorption power (absorption horsepower) of the main pump 14, which is expressed by the product of the discharge pressure and the discharge amount, from exceeding 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 travel lever 26D. The travel lever 26D includes a left traveling lever 26DL and a right traveling lever 26DR.

[0040] The left operating lever 26L is used for the rotation operation and the operation of the arm 5. When the left operating lever 26L is operated in the forward / backward direction, the hydraulic oil discharged by the pilot pump 15 is used to introduce a control pressure according to the amount of lever operation into the pilot port of the control valve 176. When the left operating lever 26L is operated in the left / right direction, the hydraulic oil discharged by the pilot pump 15 is used to introduce a control pressure according to the amount of lever operation 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 to the right pilot port of the control valve 176L and introduces hydraulic oil to 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 to the left pilot port of the control valve 176L and introduces hydraulic oil to 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 to the left pilot port of the control valve 173, and when operated in the right turning direction, it introduces hydraulic oil to the right pilot port of the control valve 173.

[0042] In the example shown in FIG. 2, the left operating lever 26L functions as an arm operating lever when operated in the forward / rearward direction, and functions as a turning operating lever when operated in the left / right direction.

[0043] In addition, a switch NS is provided on the left operation lever 26L. In this embodiment, the switch NS is a push button switch provided on 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 another position in the cabin 10.

[0044] The right operating lever 26R is used to operate the boom 4 and the bucket 6. When the right operating lever 26R is operated in the forward / backward direction, it uses the hydraulic oil discharged by the pilot pump 15 to introduce a control pressure corresponding to the amount of lever operation into the pilot port of the control valve 175. When the right operating lever 26R 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 amount of lever operation into the pilot port of the control valve 174.

[0045] Specifically, the right operating lever 26R introduces hydraulic oil to the left pilot port of the control valve 175R when operated in the boom lowering direction. Furthermore, the right operating lever 26R introduces hydraulic oil to the right pilot port of the control valve 175L and also introduces hydraulic oil to the left pilot port of the control valve 175R when operated in the boom raising direction. Furthermore, the right operating lever 26R introduces hydraulic oil to the right pilot port of the control valve 174 when operated in the bucket closing direction, and introduces hydraulic oil to the left pilot port of the control valve 174 when operated in the bucket opening direction.

[0046] In the example shown in FIG. 2, the right operating lever 26R functions as a boom operating lever when operated in the forward / rearward direction, and functions as a bucket operating lever when operated in the left / right direction.

[0047] The travel lever 26D is used to operate the crawlers. Specifically, the left travel lever 26DL is used to operate 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 forward / backward 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 171. The right travel lever 26DR is used to operate 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 forward / backward 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 172.

[0048] 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.

[0049] The operation sensor 29 includes operation sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. The operation sensor 29LA detects the content of the operation of the left operation lever 26L by the operator in the forward / rearward direction, and outputs the detected value to the controller 30. The content of the operation includes, for example, the lever operation direction, the lever operation amount (lever operation angle), etc.

[0050] Similarly, the operation sensor 29LB detects the operation of the left operating lever 26L in the left-right direction by the operator, and outputs the detected value to the controller 30. The operation sensor 29RA detects the operation of the right operating lever 26R in the forward-backward direction by the operator, and outputs the detected value to the controller 30. The operation sensor 29RB detects the operation of the right operating lever 26R in the left-right direction by the operator, and outputs the detected value to the controller 30. The operation sensor 29DL detects the operation of the left traveling lever 26DL in the forward-backward direction by the operator, and outputs the detected value to the controller 30. The operation sensor 29DR detects the operation of the right traveling lever 26DR in the forward-backward direction by the operator, and outputs the detected value to the controller 30.

[0051] The controller 30 receives the output of the operation sensor 29, and outputs a control command to the regulator 13 as necessary, thereby changing the discharge volume of the main pump 14. The controller 30 also receives the output of a control pressure sensor 19 provided upstream of the throttle (negative control throttle) 18, and outputs a control command to the regulator 13 as necessary, thereby changing the discharge volume 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.

[0052] The left center bypass pipe 40L is provided with a left throttle 18L between the most downstream control valve 176L and the hydraulic oil tank. Therefore, the flow of hydraulic oil discharged by the left main pump 14L is restricted by the left throttle 18L. The left throttle 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 reduces 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 also controlled in a similar manner.

[0053] Specifically, as shown in FIG. 2, in the case of a standby state in which none of the hydraulic actuators in the excavator 100 are operated, the hydraulic oil discharged by the left main pump 14L passes through the left center bypass pipe 40L and reaches the left throttle 18L. Then, the flow of the hydraulic oil discharged by the left main pump 14L 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 the allowable minimum discharge amount, suppressing the pressure loss (pumping loss) when the discharged hydraulic oil passes through the left center bypass pipe 40L. On the other hand, when any of the hydraulic actuators is operated, the hydraulic oil discharged by the left main pump 14L flows into the hydraulic actuator to be operated through the control valve corresponding to the hydraulic actuator to be operated. Then, the flow of the hydraulic oil discharged by the left main pump 14L reduces or eliminates the amount of hydraulic oil reaching the left throttle 18L, lowering the control pressure generated upstream of the left throttle 18L. As a result, the controller 30 increases the discharge rate of the left main pump 14L to circulate sufficient hydraulic oil to the hydraulic actuator to be operated, ensuring the drive of the hydraulic actuator to be operated. The controller 30 also controls the discharge rate of the right main pump 14R in a similar manner.

[0054] With the above-described configuration, the hydraulic system of Fig. 2 can suppress unnecessary energy consumption in the main pump 14 in a standby state. The unnecessary energy consumption includes pumping loss caused in the center bypass pipe 40 by the hydraulic oil discharged from the main pump 14. Furthermore, when operating a hydraulic actuator, the hydraulic system of Fig. 2 can reliably supply necessary and sufficient hydraulic oil from the main pump 14 to the hydraulic actuator to be operated.

[0055] That is, the controller 30 controls the regulator 13 so that the discharge amount is the smaller of a first discharge amount calculated so that the absorption power (absorption horsepower) of the main pump 14, which is expressed as the product of the discharge pressure and the discharge amount, does not exceed the output power (output horsepower) of the engine 11, and a second discharge amount calculated based on the control pressure detected by the control pressure sensor 19.

[0056] 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 referred to as "cylinder pressure sensors." In addition, a left swing pressure sensor S10L and a right swing pressure sensor S10R are attached to the swing hydraulic motor 2A.

[0057] The boom rod pressure sensor S7R detects the pressure in the rod side oil chamber of the boom cylinder 7 (hereinafter referred to as the "boom rod pressure"), and the boom bottom pressure sensor S7B detects the pressure in the bottom side oil chamber of the boom cylinder 7 (hereinafter referred to as the "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 the "arm rod pressure"), and the arm bottom pressure sensor S8B detects the pressure in the bottom side oil chamber of the arm cylinder 8 (hereinafter referred to as the "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 the "bucket rod pressure"), and the bucket bottom pressure sensor S9B detects the pressure in the bottom side oil chamber of the bucket cylinder 9 (hereinafter referred to as the "bucket bottom pressure"). The left swing pressure sensor S10L detects the pressure of the hydraulic oil in the left port of the swing hydraulic motor 2A. The right swing pressure sensor S10R detects the pressure of the hydraulic oil in the right port of the swing hydraulic motor 2A. The values ​​detected by each sensor are transmitted to the controller 30 .

[0058] The controller 30 also includes a failure determination unit 30X, a control valve control unit 30Y, and a regulator control unit 30Z.

[0059] The failure determination unit 30X determines whether or not there is a failure in the regulator 13. Note that a method for determining whether or not there is a failure in the regulator 13 will be described later (see FIG. 6S101, etc.).

[0060] The control valve control unit 30Y receives the operation amount of the operating device 26 detected by the operation sensor 29, and controls the control valves 171-176 by outputting a control command (electrical signal) to a proportional valve 31 (also see Figure 4) which controls the pilot pressure (secondary pressure) supplied to the control valves 171-176.

[0061] The regulator control unit 30Z controls the regulator 13 by outputting a control command (electrical signal) to a tilt control proportional valve 37 (see FIG. 3 described later) that controls the pilot pressure (secondary pressure) supplied to the regulator 13.

[0062] Next, a pump discharge amount control circuit 300 that controls the discharge amount of the main pump 14 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of the pump discharge amount control circuit 300.

[0063] The pump discharge amount control circuit 300 includes a regulator 13, a displacement control proportional valve 37, a controller 30, a pilot pump 15, and a regulator pilot pressure sensor , and controls the discharge amount of the variable displacement main pump .

[0064] The regulator 13 includes a servo switching valve 33, a control-side piston 34, and a servo cylinder 35. The regulator 13 changes the tilt angle of the swash plate 14A of the main pump 14 in response to the pilot pressure input to the control-side piston 34 to control the discharge amount of the main pump 14.

[0065] The servo switching valve 33 has a spool 33A and a sleeve 33B. A control side piston 34 is attached to one end of the spool 33A, and a spring 33C is attached to the other end of the spool 33A. The servo switching valve 33 has three switching positions (a), (b), and (c). When switched to the switching position (a), the discharge rate of the main pump 14 decreases, when switched to the switching position (b), the discharge rate of the main pump 14 is maintained, and when switched to the switching position (c), the discharge rate of the main pump 14 increases.

[0066] When the control side piston 34 receives pilot pressure from the tilt control proportional valve 37, it urges the spool 33A in a direction that decreases the discharge rate of the main pump 14. When pilot pressure is received from the tilt control proportional valve 37, normal electrical control is performed. The spring 33C urges the spool 33A in a direction that increases the discharge rate of the main pump 14. The sleeve 33B is mechanically connected to the servo piston 35A in the servo cylinder 35 via the connecting rod 36, and moves following the movement of the spool 33A.

[0067] The servo cylinder 35 includes a servo piston 35A therein. The servo piston 35A is connected to the swash plate 14A of the main pump 14 and changes the tilt angle of the swash plate 14A. The cross-sectional area of ​​the servo piston 35A is larger at the left end and smaller at the right end in FIG. 3. The discharge pressure of the main pump 14 is always applied to the right end of the servo piston 35A, but the discharge pressure of the main pump 14 is applied to the left end of the servo piston 35A when the servo switching valve 33 is switched to the switching position (a). Since the cross-sectional area of ​​the servo piston 35A is larger at the left end than at the right end, when the servo switching valve 33 is switched to the switching position (a), the servo piston 35A moves to the right in FIG. 3, and the discharge amount of the main pump 14 decreases.

[0068] The tilt control proportional valve 37 is an electromagnetic proportional valve, and operates in response to a control command (current command) output by the controller 30 via an electric signal line 30a. The tilt control proportional valve 37 has a solenoid unit 37A at one end of a spool. When an electric signal is sent from the controller 30 to the solenoid unit 37A, the solenoid unit 37A adjusts the biasing force on the spool to increase the opening degree (degree of communication) in accordance with the content of the electric signal, and the opening degree of the tilt control proportional valve 37 is switched. In addition, the tilt control proportional valve 37 has a spring 37B at the other end of the spool. The spring 37B biases the spool in a direction to decrease the opening degree.

[0069] During normal electrical control, the tilt control proportional valve 37 switches its opening in response to a control command (electrical signal sent to the solenoid unit 37A) from the controller 30. This controls the pilot pressure supplied from the pilot pump 15 to the control-side piston 34 (regulator 13). The regulator 13 then changes the tilt angle of the swash plate 14A of the main pump 14 in response to the pilot pressure input to the control-side piston 34, thereby controlling the discharge amount of the main pump 14.

[0070] A regulator pilot pressure sensor 38 that detects the pilot pressure is provided in the pilot line that connects the tilt control proportional valve 37 and the control side piston 34 (regulator 13). The value detected by the regulator pilot pressure sensor 38 is transmitted to the controller 30.

[0071] Next, a configuration for the controller 30 to operate the actuators using the machine control function will be described with reference to Fig. 4. Fig. 4 is a diagram of a part of the hydraulic system. Specifically, Fig. 4 is a diagram of the hydraulic system portion related to the operation of the boom cylinder 7.

[0072] 4, the hydraulic system includes a proportional valve 31. The proportional valve 31 is an electromagnetic proportional valve, and operates in response to a control command (current command) output by the controller 30. The proportional valve 31 includes proportional valves 31BL and 31BR.

[0073] The proportional valve 31 functions as a control valve for machine control. The proportional valve 31 is disposed in a pipe connecting the pilot pump 15 and a pilot port of a corresponding control valve in the control valve unit 17, and is configured to be able to change the flow passage area of ​​the pipe. In this embodiment, the proportional valve 31 operates in response 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. Then, the controller 30 can apply the pilot pressure generated by the proportional valve 31 to the pilot port of the corresponding control valve.

[0074] With this configuration, the controller 30 can operate the hydraulic actuator corresponding to a specific operating device 26 even when no operation is being performed on that specific operating device 26. Furthermore, the controller 30 can forcibly stop the operation of the hydraulic actuator corresponding to that specific operating device 26 even when an operation is being performed on that specific operating device 26.

[0075] For example, as shown in Fig. 4, the right operating lever 26R is used to operate the boom 4. Specifically, the right operating lever 26R uses hydraulic oil discharged by the pilot pump 15 to apply a pilot pressure corresponding to the operation in the forward / rearward direction to the pilot port of the control valve 175. More specifically, when the right operating lever 26R is operated in the boom-up direction (rearward), it applies a pilot pressure corresponding to the operation amount to the left pilot port of the control valve 175R. Also, when the right operating lever 26R is operated in the boom-down direction (forward), it applies a pilot pressure corresponding to the operation amount to the right pilot port of the control valve 175R.

[0076] The operation sensor 29RA detects the content of the operation of the right operating lever 26R in the forward / rearward direction by the operator, and outputs the detected value to the controller 30.

[0077] The proportional valve 31BL operates in response to a control command (current command) output by the controller 30. The proportional valve 31BL adjusts the pilot pressure by the hydraulic oil introduced from the pilot pump 15 to the left pilot port of the control valve 175R via the proportional valve 31BL. The proportional valve 31BR operates in response to a control command (current command) output by the controller 30. The proportional valve 31BR adjusts the pilot pressure by the hydraulic oil introduced from the pilot pump 15 to the right pilot port of the control valve 175R via the proportional valve 31BR. The proportional valve 31BL can adjust the pilot pressure so that the control valve 175R can be stopped at any valve position. The proportional valve 31BR can adjust the pilot pressure so that the control valve 175R can be stopped at any valve position.

[0078] A pilot pressure sensor 32BL for detecting pilot pressure is provided in a pilot line connecting the proportional valve 31BL and one port of the control valve 175 (the left port of the control valve 175R). A pilot pressure sensor 32BR for detecting pilot pressure is provided in a pilot line connecting the proportional valve 31BR and the other port of the control valve 175 (the right port of the control valve 175R). Values ​​detected by the pilot pressure sensors 32BL and 32BR are transmitted to the controller 30.

[0079] With this configuration, controller 30 can supply hydraulic oil discharged from pilot pump 15 to the left pilot port of control valve 175R via proportional valve 31BL in response to a boom-raising operation by the operator. Also, controller 30 can supply hydraulic oil discharged from pilot pump 15 to the left pilot port of control valve 175R via proportional valve 31BL, regardless of a boom-raising operation by the operator. In other words, controller 30 can raise boom 4 in response to a boom-raising operation by the operator or regardless of a boom-raising operation by the operator.

[0080] Furthermore, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the right pilot port of the control valve 175R via the proportional valve 31BR in response to the boom lowering operation by the operator. Furthermore, the controller 30 can supply the hydraulic oil discharged by the pilot pump 15 to the right pilot port of the control valve 175R via the proportional valve 31BR, regardless of the boom lowering operation by the operator. In other words, the controller 30 can lower the boom 4 in response to the boom lowering operation by the operator or regardless of the boom lowering operation by the operator.

[0081] 4, the configuration in which the controller 30 controls the proportional valves 31BL, 31BR and supplies the pilot pressure to the control valve 175R has been described. Similarly, the controller 30 controls a proportional valve (not shown) and supplies the pilot pressure to the control valve 175L.

[0082] Furthermore, with this configuration, even when the operator is performing a boom-raising operation, the controller 30 can, as necessary, reduce the pilot pressure acting on the boom-raising side pilot ports of the control valve 175 (the left pilot port of the control valve 176R and the right pilot port of the control valve 175L) to forcibly stop the raising operation of the boom 4. The same applies to the case where the lowering operation of the boom 4 is forcibly stopped when the operator is performing a boom-lowering operation.

[0083] Although detailed description will be omitted, the same applies to the case where the operation of the arm 5 is forcibly stopped when the operator is performing an arm opening operation or an arm closing operation, the case where the operation of the bucket 6 is forcibly stopped when the operator is performing a bucket closing operation or a bucket opening operation, and the case where the rotation operation of the upper rotating body 3 is forcibly stopped when the operator is performing a rotation operation, and the case where the traveling operation of the lower traveling body 1 is forcibly stopped when the operator is performing a traveling operation.

[0084] The excavator 100 may be configured to automatically move the lower traveling structure 1 forward and backward. In this case, the hydraulic system portion related to the operation of the left traveling hydraulic motor 2ML and the hydraulic system portion related to the operation of the right traveling hydraulic motor 2MR may be configured in the same manner as the hydraulic system portion related to the operation of the boom cylinder 7, etc.

[0085] Although the description has been given of an electric control lever as a form of the operation device 26, a hydraulic operation lever may be adopted instead of the electric operation lever. In this case, the lever operation amount of the hydraulic operation 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 disposed between the operation device 26 as a hydraulic operation lever and the pilot port 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 manual operation is performed using the operation device 26 as a hydraulic operation lever, the operation device 26 can move each control valve by increasing or decreasing the pilot pressure in response to the lever operation amount. Also, each control valve may be configured as 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.

[0086] Next, the discharge amount control of the main pump 14 will be described with reference to FIG. 5. FIG. 5 is a graph showing the relationship between the pump pressure, the pump flow rate, and the torque. In FIG. 5, the horizontal axis shows the total pump pressure (P1+P2) of the pump pressure P1 (discharge pressure detected by the discharge pressure sensor 28L) of the left main pump 14L and the pump pressure P2 (discharge pressure detected by the discharge pressure sensor 28R) of the right main pump 14R. One (left) vertical axis shows the discharge amount (pump flow rate) of the left main pump 14L and the right main pump 14R. The other (right) vertical axis shows the torque of the left main pump 14L and the right main pump 14R. In the graph of FIG. 5, the pump flow rate of the main pump 14 is shown by a thick solid line, and the torque of the main pump 14 is shown by a thick dashed line.

[0087] The first control region S1 is a region where the pump pressure is less than pressure P0. In the first control region S1, the regulator control unit 30Z controls the pump flow rate of the main pump 14 to be constant at a maximum flow rate Q1. The torque of the main pump 14 is expressed as the product of the discharge pressure (pump pressure) of the main pump 14 and the discharge rate (pump flow rate) of the main pump 14. In the first control region S1, the torque of the main pump 14 increases as the pump pressure increases.

[0088] Here, the controller 30 (regulator control section 30Z) controls the tilt control proportional valve 37 (see FIG. 3) to be closed. In other words, the controller 30 does not output a control command (electrical signal) to the tilt control proportional valve 37. As a result, the spool of the tilt control proportional valve 37 is biased by the spring 37B in a direction to reduce the opening degree, and the tilt control proportional valve 37 is closed. In addition, the spool 33A is biased by the spring 33C, and the servo switching valve 33 is switched to the switching position (c). In addition, the servo piston 35A of the servo cylinder 35 moves to the left. As a result, the swash plate 14A is tilted to the maximum, and the discharge amount of the main pump 14 is constant at the maximum flow rate Q1.

[0089] The second control region S2 is a region where the pump pressure is equal to or higher than pressure P0. In the second control region S2, the regulator control unit 30Z controls the torque of the main pump 14 to be constant at a maximum torque T1. Here, in the graph of FIG. 5, the outputtable torque T0 of the engine 11 is indicated by a thick two-dot chain line. The maximum torque T1 is set to be smaller than the outputtable torque T0 of the engine 11. In other words, the regulator control unit 30Z controls the maximum torque T1 of the main pump 14 so as not to exceed the outputtable torque T0 of the engine 11, thereby preventing engine stall.

[0090] Here, the controller 30 (regulator control section 30Z) outputs a control command (electrical signal) to the tilt control proportional valve 37 (see FIG. 3). As a result, in response to the control command, the opening of the tilt control proportional valve 37 is controlled, the pilot pressure of the regulator 13 is controlled, and the tilt angle of the swash plate 14A is controlled, thereby controlling the discharge rate of the main pump 14. That is, in the second control region S2, the discharge rate of the main pump 14 is controlled to decrease as the pump pressure increases, and the torque of the main pump 14 is controlled to be constant at the maximum torque T1.

[0091] Now, a case will be described as an example in which a malfunction occurs in the electrical system of the pump discharge control circuit 300 shown in Fig. 3, and a control command (electrical signal) does not reach the solenoid unit 37A from the controller 30 (regulator control unit 30Z). In this case, the tilt control proportional valve 37 is closed by the biasing force of the spring 37B. As a result, pilot pressure is not supplied to the downstream side of the tilt control proportional valve 37, and the servo switching valve 33 switches to the switching position (c). Also, the servo piston 35A of the servo cylinder 35 moves to the left. As a result, the swash plate 14A is tilted to the maximum, and the discharge volume of the main pump 14 is fixed at the maximum flow rate Q1.

[0092] 5, when the pump pressure (P1+P2) increases, the pump flow rate is fixed at the maximum flow rate Q1, as indicated by arrow 501 and the dashed line. Also, as indicated by arrow 502 and the dashed line, the torque continues to increase as the pump pressure (P1+P2) increases. This causes the torque of the main pump 14 to exceed the output torque T0 of the engine 11, which may cause an unintended stop (engine stall, drive source stall) of the engine 11, which is the drive source.

[0093] Next, with reference to Figs. 6 to 8, an example of a control method for enabling the operation of the shovel 100 while preventing engine stall (driving source stall) will be described.

[0094] <First engine stall prevention control> FIG. 6 is a flowchart showing the first engine stall prevention control of the shovel 100.

[0095] In step S101, the failure determination unit 30X of the controller 30 performs a failure determination of the regulator 13.

[0096] Here, the failure of the regulator 13 refers to a state in which the tilt angle of the swash plate 14A of the regulator 13 cannot be controlled by the regulator control section 30Z of the controller 30. Specifically, this is a state in which the tilt control proportional valve 37 is fixed in a closed position and the swash plate 14A is fixed at the maximum tilt position due to a malfunction of the electrical system of the pump discharge control circuit 300 or the like.

[0097] The failure determination unit 30X determines whether or not there is a failure in the regulator 13 based on the following first to third failure determination methods.

[0098] In the first failure judgment method, the failure judgment unit 30X judges that the regulator 13 has failed when the difference between the estimated pilot pressure based on the control command value from the controller 30 (control valve control unit 30Y) to the tilt control proportional valve 37 and the actual pilot pressure detected by the regulator pilot pressure sensor 38 is greater than or equal to a threshold value.

[0099] In the second failure determination method, the failure determination unit 30X determines that the regulator 13 has failed when the difference between the rotation speed command value of the engine 11 and the actual rotation speed of the engine 11 is equal to or greater than a threshold value.

[0100] Here, the engine 11 is provided with an engine speed sensor (drive source speed sensor) (not shown) that detects the actual speed of the engine 11. The controller 30 has a speed command value of the engine 11. The speed command value of the controller 30 is received by an ECU (Engine Control Unit) (not shown). When the actual speed of the engine 11 falls below the speed command value of the engine 11 due to a load being applied to the engine 11, the ECU increases the fuel injection amount of the engine 11 and controls the actual speed of the engine 11 to return to the speed command value of the engine 11. At this time, if the regulator 13 is broken and the torque of the main pump 14 is large, the actual speed of the engine 11 does not reach the speed command value of the engine 11, and a difference occurs between the speed command value of the engine 11 and the actual speed of the engine 11. The failure determination unit 30X determines a failure of the regulator 13 based on whether or not this difference is equal to or greater than a threshold value.

[0101] In the third failure determination method, the failure determination unit 30X determines that the regulator 13 has failed when the difference between the rotation speed command value of the engine 11 and the actual rotation speed of the engine 11 is equal to or greater than a threshold and the amount of fuel supplied to the engine 11 is equal to or greater than a threshold.

[0102] As described above, the engine 11 is provided with a sensor (not shown) for detecting the actual rotation speed of the engine 11. The controller 30 has a rotation speed command value of the engine 11. The ECU receives the rotation speed command value of the controller 30. When the actual rotation speed of the engine 11 falls below the rotation speed command value of the engine 11 due to a load being applied to the engine 11, the ECU increases the fuel injection amount of the engine 11 and controls the actual rotation speed of the engine 11 to return to the rotation speed command value of the engine 11. At this time, if the regulator 13 is broken and the torque of the main pump 14 is large, the actual rotation speed of the engine 11 does not reach the rotation speed command value of the engine 11, and a difference occurs between the rotation speed command value of the engine 11 and the actual rotation speed of the engine 11. If this difference is equal to or greater than a threshold value and the amount of fuel supplied to the engine 11 is equal to or greater than a threshold value, the failure determination unit 30X determines that the regulator 13 is broken. The amount of fuel supplied to the engine 11 may be an actual amount of fuel supplied detected by a flow sensor, or may be a fuel supply amount command value from an ECU to a fuel supply device (not shown).

[0103] If it is determined that the regulator 13 is malfunctioning (S101 YES), the process of the controller 30 proceeds to step S102. On the other hand, if it is determined that the regulator 13 is not malfunctioning (S101 NO), the process of the controller 30 proceeds to step S104.

[0104] In step S102, the control valve control section 30Y of the controller 30 determines whether the pump pressure is equal to or higher than a threshold value.

[0105] Here, it is determined whether the total pump pressure (P1+P2) of the pump pressure P1 (discharge pressure) of the left main pump 14L detected by the discharge pressure sensor 28L and the pump pressure P2 (discharge pressure) of the right main pump 14R detected by the discharge pressure sensor 28R is equal to or greater than a predetermined threshold value. The predetermined threshold value is a pressure P0 (see FIG. 5) that separates the first control region S1 from the second control region S2. Note that the predetermined threshold value may be set to a value smaller than the pressure P0.

[0106] In other words, a region where the pump pressure is equal to or higher than the threshold value is a region where there is a risk of engine stall occurring, as indicated by arrow 502 in FIG.

[0107] If the controller 30 determines that the pump pressure is equal to or higher than the threshold (S102 YES), the process proceeds to step S103. On the other hand, if the controller 30 determines that the pump pressure is not equal to or higher than the threshold (S102 NO), the process proceeds to step S104.

[0108] In step S103, the control valve control section 30Y of the controller 30 controls the proportional valve 31 with an upper limit based on the operation amount of the operating device 26. Here, the control command from the controller 30 (control valve control section 30Y) to the proportional valve 31 is limited so that the pump pressure P1 of the left main pump 14L is equal to or lower than P0 / 2 (threshold value, pump pressure limit value) and the pump pressure P2 of the right main pump 14R is equal to or lower than P0 / 2 (threshold value, pump pressure limit value).

[0109] That is, the controller 30 (control valve control unit 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. Here, the control command value corresponding to the limit value of the pump pressure is set as the control command limit value. When the control command value based on the operation amount is less than the control command limit value, the controller 30 commands the proportional valve 31 to the control command value based on the operation amount. On the other hand, when the control command value based on the operation amount is equal to or greater than the control command limit value, the controller 30 commands the proportional valve 31 to the control command limit value.

[0110] This limits the maximum value of the opening area of ​​the proportional valve 31. Also, the maximum value of the pilot pressure acting on the control valves 171-176 is limited. Also, the maximum value of the spool stroke of the control valves 171-176 is limited. Also, the minimum value of the opening area of ​​the PT opening (the opening of the control valve connected to the center bypass pipe 40 that communicates from the main pump 14 to the hydraulic oil tank) of the control valves 171-176 is limited. This makes it possible to keep the pump pressure (P1+P2) within a range equal to or less than a predetermined threshold value.

[0111] In step S104, the control valve control section 30Y of the controller 30 controls the proportional valve 31 based on the operation amount of the operation device 26. That is, the controller 30 (control valve control section 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. The controller 30 issues a control command value based on the operation amount to the proportional valve 31.

[0112] In this way, according to the first engine stall prevention control of the shovel 100, the shovel 100 can be operated while preventing engine stall. That is, according to the first engine stall prevention control of the shovel 100, the pump pressure (P1+P2) is controlled so as not to exceed a predetermined threshold value. For example, the threshold value is set to pressure P0 (see FIG. 5), and the pump pressure (P1+P2) is controlled so as not to exceed pressure P0 (S103). As a result, the torque of the main pump 14 is controlled within a range not exceeding torque T1. In other words, the torque of the main pump 14 is controlled so as not to exceed the outputtable torque T0 of the engine 11, thereby preventing engine stall.

[0113] Moreover, according to the excavator 100, engine stall can be prevented without using a redundant device in the pump discharge amount control circuit 300. This makes it possible to reduce the cost of the redundant device.

[0114] <Second engine stall prevention control> FIG. 7 is a flowchart showing the second engine stall prevention control of the shovel 100.

[0115] In step S201, the failure determination unit 30X of the controller 30 performs a failure determination of the regulator 13.

[0116] Here, the failure of the regulator 13 refers to a state in which the tilt angle of the swash plate 14A of the regulator 13 cannot be controlled by the regulator control section 30Z of the controller 30. Specifically, this is a state in which the tilt control proportional valve 37 is fixed in a closed position and the swash plate 14A is fixed at the maximum tilt position due to a malfunction of the electrical system of the pump discharge control circuit 300 or the like.

[0117] Moreover, similarly to step S101, the failure determination unit 30X determines whether or not there is a failure in the regulator 13 based on the first to third failure determination methods described above.

[0118] If it is determined that the regulator 13 is malfunctioning (S201 YES), the process of the controller 30 proceeds to step S202. On the other hand, if it is determined that the regulator 13 is not malfunctioning (S201 NO), the process of the controller 30 proceeds to step S203.

[0119] In step S202, the control valve control section 30Y of the controller 30 controls the proportional valve 31 with an upper limit based on the operation amount of the operating device 26. Here, the control command from the controller 30 (control valve control section 30Y) to the proportional valve 31 is limited so that the pump pressure P1 of the left main pump 14L is equal to or lower than P0 / 2 (threshold value, pump pressure limit value) and the pump pressure P2 of the right main pump 14R is equal to or lower than P0 / 2 (threshold value, pump pressure limit value).

[0120] That is, the controller 30 (control valve control unit 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. Here, the control command value corresponding to the limit value of the pump pressure is set as the control command limit value. When the control command value based on the operation amount is less than the control command limit value, the controller 30 commands the proportional valve 31 to the control command value based on the operation amount. On the other hand, when the control command value based on the operation amount is equal to or greater than the control command limit value, the controller 30 commands the proportional valve 31 to the control command limit value.

[0121] This limits the maximum value of the opening area of ​​the proportional valve 31. Also, the maximum value of the pilot pressure acting on the control valves 171-176 is limited. Also, the maximum value of the spool stroke of the control valves 171-176 is limited. Also, the minimum value of the opening area of ​​the PT opening (the opening of the control valve connected to the center bypass pipe 40 that communicates from the main pump 14 to the hydraulic oil tank) of the control valves 171-176 is limited. This makes it possible to keep the pump pressure (P1+P2) within a range equal to or less than a predetermined threshold value.

[0122] In step S203, the control valve control section 30Y of the controller 30 controls the proportional valve 31 based on the operation amount of the operation device 26. That is, the controller 30 (control valve control section 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. The controller 30 issues a control command value based on the operation amount to the proportional valve 31.

[0123] In this way, according to the second engine stall prevention control of the shovel 100, the shovel 100 can be operated while preventing engine stall. That is, according to the second engine stall prevention control of the shovel 100, the pump pressure (P1+P2) is controlled so as not to exceed a predetermined threshold value. For example, the threshold value is set to pressure P0 (see FIG. 5), and the pump pressure (P1+P2) is controlled so as not to exceed pressure P0 (S202). As a result, the torque of the main pump 14 is controlled within a range not exceeding torque T1. In other words, the torque of the main pump 14 is controlled so as not to exceed the outputtable torque T0 of the engine 11, thereby preventing engine stall.

[0124] Moreover, according to the excavator 100, engine stall can be prevented without using a redundant device in the pump discharge amount control circuit 300. This makes it possible to reduce the cost of the redundant device.

[0125] <Third engine stall prevention control> FIG. 8 is a flowchart showing the third engine stall prevention control of the shovel 100.

[0126] In step S301, the failure determination unit 30X of the controller 30 performs a failure determination of the regulator 13.

[0127] Here, the failure of the regulator 13 refers to a state in which the tilt angle of the swash plate 14A of the regulator 13 cannot be controlled by the regulator control section 30Z of the controller 30. Specifically, this is a state in which the tilt control proportional valve 37 is fixed in a closed position and the swash plate 14A is fixed at the maximum tilt position due to a malfunction of the electrical system of the pump discharge control circuit 300 or the like.

[0128] Moreover, similarly to step S101, the failure determination unit 30X determines whether or not there is a failure in the regulator 13 based on the first to third failure determination methods described above.

[0129] If it is determined that the regulator 13 is malfunctioning (S301 YES), the process of the controller 30 proceeds to step S302. On the other hand, if it is determined that the regulator 13 is not malfunctioning (S301 NO), the process of the controller 30 proceeds to step S305.

[0130] In step S302, the control valve control section 30Y of the controller 30 judges whether or not both systems are in operation. Here, as shown in Fig. 2, in the hydraulic system, control valves 171, 173, 175L, and 176L (directional control valves of the first system) to which hydraulic oil is supplied from the left main pump (first hydraulic pump) 14L are provided, and control valves 172, 174, 175R, and 176R (directional control valves of the second system) to which hydraulic oil is supplied from the right main pump (second hydraulic pump) 14R are provided.

[0131] If at least one of the control valves 171, 173, 175L, 176L of the first system (left system) is operated and none of the control valves 172, 174, 175R, 176R of the second system (right system) is operated, it is determined that only the left system is operated (S302: NO).

[0132] When at least one of the control valves 172, 174, 175R, 176R of the second system (right system) is operated and none of the control valves 171, 173, 175L, 176L of the first system (left system) is operated, it is determined that only the right system is operated (S302: NO).

[0133] When at least one of the control valves 171, 173, 175L, 176L of the first system (left system) is operated and at least one of the control valves 172, 174, 175R, 176R of the second system (right system) is operated, it is determined that both systems are operated (S302 YES).

[0134] In step S303, the control valve control section 30Y of the controller 30 controls the proportional valve 31 based on the operation amount of the operating device 26 at the first upper limit. Here, the control command from the controller 30 (control valve control section 30Y) to the proportional valve 31 is limited so that the pump pressure P1 of the left main pump 14L is equal to or lower than P0 / 2 (first upper limit, limit value of pump pressure) and the pump pressure P2 of the right main pump 14R is equal to or lower than P0 / 2 (first upper limit, limit value of pump pressure).

[0135] That is, the controller 30 (control valve control unit 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. Here, the control command value corresponding to the limit value (first upper limit) of the pump pressure is set as the control command limit value. When the control command value based on the operation amount is less than the control command limit value, the controller 30 commands the proportional valve 31 to the control command value based on the operation amount. On the other hand, when the control command value based on the operation amount is equal to or greater than the control command limit value, the controller 30 commands the proportional valve 31 to the control command limit value.

[0136] This limits the maximum value of the opening area of ​​the proportional valve 31. Also, the maximum value of the pilot pressure acting on the control valves 171-176 is limited. Also, the maximum value of the spool stroke of the control valves 171-176 is limited. Also, the minimum value of the opening area of ​​the PT opening (the opening of the control valve connected to the center bypass pipe 40 that communicates from the main pump 14 to the hydraulic oil tank) of the control valves 171-176 is limited. This makes it possible to keep the pump pressure (P1+P2) within a range equal to or less than a predetermined threshold value.

[0137] In step S304, the control valve control section 30Y of the controller 30 controls the proportional valve 31 based on the operation amount of the operating device 26 at a second upper limit higher than the first upper limit. Here, if it is determined in step S302 that only the left system is operated, the pump pressure P2 of the right main pump 14R is set to the standby pump pressure PST corresponding to the standby flow rate, and the control command from the controller 30 (control valve control section 30Y) to the proportional valve 31 is limited to a maximum value so that the pump pressure P1 of the left main pump 14L is equal to or lower than (P0-PST) (second upper limit, limit value of pump pressure). Also, if it is determined in step S302 that only the right system is operated, the pump pressure P1 of the left main pump 14L is set to the standby pump pressure PST corresponding to the standby flow rate, and the control command from the controller 30 (control valve control section 30Y) to the proportional valve 31 is limited to a maximum value so that the pump pressure P2 of the right main pump 14R is equal to or lower than (P0-PST) (second upper limit, limit value of pump pressure).

[0138] That is, the controller 30 (control valve control unit 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. Here, the control command value corresponding to the limit value (second upper limit) of the pump pressure is set as the control command limit value. When the control command value based on the operation amount is less than the control command limit value, the controller 30 commands the proportional valve 31 to the control command value based on the operation amount. On the other hand, when the control command value based on the operation amount is equal to or greater than the control command limit value, the controller 30 commands the proportional valve 31 to the control command limit value.

[0139] In comparison with the case where only one system is operated (S304) and the case where both systems are operated (S303), the pressure and / or supply amount of hydraulic oil supplied to the hydraulic actuator can be increased. For example, by operating only the left travel lever 26DL, the pressure and / or supply amount of hydraulic oil supplied to the left traveling hydraulic motor 2ML can be increased while suppressing engine stall even when a failure occurs. Also, for example, by operating only the right travel lever 26DR, the pressure and / or supply amount of hydraulic oil supplied to the right traveling hydraulic motor 2MR can be increased while suppressing engine stall even when a failure occurs. As a result, even if a failure occurs on rough ground, the excavator 100 can be moved from the rough ground by alternately operating the crawlers of the excavator 100 while preventing engine stall.

[0140] In step S305, the control valve control section 30Y of the controller 30 controls the proportional valve 31 based on the operation amount of the operation device 26. That is, the controller 30 (control valve control section 30Y) determines a control command value for the proportional valve 31 based on the operation amount detected by the operation sensor 29. The controller 30 issues a control command value based on the operation amount to the proportional valve 31.

[0141] In this way, according to the third engine stall prevention control of the shovel 100, the shovel 100 can be operated while preventing engine stall. That is, according to the third engine stall prevention control of the shovel 100, the pump pressure (P1+P2) is controlled so as not to exceed a predetermined threshold value. For example, the threshold value is set to pressure P0 (see FIG. 5), and the pump pressure (P1+P2) is controlled so as not to exceed pressure P0 (S303, 304). As a result, the torque of the main pump 14 is controlled within a range not exceeding torque T1. In other words, the torque of the main pump 14 is controlled so as not to exceed the outputtable torque T0 of the engine 11, thereby preventing engine stall.

[0142] Moreover, when only one system is operated (S302·NO, S304), the pump pressure of the operated system is controlled so as not to exceed a second upper limit that is higher than the first upper limit (304). This makes it possible to increase the pressure and / or supply amount of the hydraulic oil supplied to the hydraulic actuator.

[0143] Moreover, according to the excavator 100, engine stall can be prevented without using a redundant device in the pump discharge amount control circuit 300. This makes it possible to reduce the cost of the redundant device.

[0144] An example of engine stall prevention control has been described using the excavator 100 having the engine 11 as a drive source for driving the main pump 14 and the pilot pump 15 as an example, but the present invention is not limited to this. That is, the present invention may be applied to drive source stall prevention control in an excavator having a drive source other than an engine. For example, the present invention may be applied to motor stall prevention control (drive source stall prevention control) in an excavator having a drive motor as a drive source for driving the main pump 14 and the pilot pump 15. Even in this configuration, motor stall (drive source stall) can be prevented without using a redundant device in the pump discharge control circuit 300. That is, it is possible to prevent the torque of the main pump 14 from exceeding the output torque of the drive motor, causing an unintended stop (motor stall, drive source stall) of the drive motor, which is the drive source. This makes it possible to reduce the cost of the redundant device.

[0145] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0146] 1 Undercarriage 2 Swivel mechanism 2A Swing Hydraulic Motor (Hydraulic Actuator) 2M Travel hydraulic motor (hydraulic actuator) 2MR Right travel hydraulic motor (hydraulic actuator) 2ML Left Travel Hydraulic Motor (Hydraulic Actuator) 3. Upper rotating body 4. Boom 5 Arm 6 Bucket 7 Boom cylinder (hydraulic actuator) 8 Arm cylinder (hydraulic actuator) 9 Bucket cylinder (hydraulic actuator) 11 Engine (power source) 13 Regulator 13L Left regulator 13R Right regulator 14 Main pump (hydraulic pump) 14A Swash plate 14L Left main pump (first hydraulic pump) 14R Right main pump (second hydraulic pump) 15 Pilot pump 17 Control valve unit 171~176 Control valves (directional control valves) 26 Operating device 29 Operation Sensor 30 Controller (control device) 30X Failure determination section 30Y Control valve control section 30Z Regulator control unit 31 Proportional valve (electromagnetic proportional valve) 37 Tilt control proportional valve 38 Regulator pilot pressure sensor 100 Shovel S1 First control area S2 Second control area P0 pressure (the pressure that separates the first and second control regions)

Claims

1. A lower running body; An upper rotating body that can rotate relative to the lower traveling body; A driving source; A hydraulic pump driven by the drive source; A regulator for controlling a flow rate of hydraulic oil discharged from the hydraulic pump; A hydraulic actuator; a directional control valve that controls hydraulic oil supplied from the hydraulic pump to the hydraulic actuator; An operating device; A control device, The control device includes: a failure determination unit that determines a failure of the regulator; a control valve control unit to which an operation amount of the operation device is input and which controls the directional control valve, The control valve control unit is When the failure determination unit determines that the regulator has failed, the directional control valve is controlled by a drive source stall prevention control. Shovel.

2. a tilt control proportional valve for controlling the pilot pressure of the regulator; a regulator pilot pressure sensor for detecting an actual pilot pressure supplied to the regulator in a pilot line connecting the tilt control proportional valve and the regulator, The failure determination unit is When a difference between an estimated pilot pressure based on a control command value to the tilt control proportional valve and the actual pilot pressure detected by the regulator pilot pressure sensor is equal to or greater than a threshold value, it is determined that the regulator has failed. The shovel according to claim 1.

3. A drive source rotation speed sensor for detecting an actual rotation speed of the drive source is further provided, The failure determination unit is When a difference between a rotation speed command value of the driving source and the actual rotation speed detected by the driving source rotation speed sensor is equal to or greater than a threshold value, it is determined that the regulator has failed. The shovel according to claim 1.

4. A drive source rotation speed sensor for detecting an actual rotation speed of the drive source is further provided, The failure determination unit is a determination that the regulator has failed when a difference between a rotation speed command value of the driving source and the actual rotation speed detected by the driving source rotation speed sensor is equal to or greater than a threshold value and an amount of fuel supplied to the driving source is equal to or greater than a threshold value; The shovel according to claim 1.

5. The drive source stall prevention control controls the directional control valve so that the pump pressure of the hydraulic pump does not exceed a predetermined threshold pump pressure. A shovel according to any one of claims 1 to 4.

6. A tilt control proportional valve for controlling the pilot pressure of the regulator is further provided. The control device further includes a regulator control unit that controls the tilt angle of the swash plate of the regulator by controlling the tilt control proportional valve, The regulator control unit is A first control region in which the flow rate of the hydraulic pump is controlled to be constant, and a second control region in which the torque of the hydraulic pump is controlled to be constant, The threshold pump pressure is a pressure that separates the first control region from the second control region. The shovel according to claim 5.

7. The control valve control unit is when the failure determination unit determines that the regulator has failed and the pump pressure of the hydraulic pump exceeds a predetermined threshold, the minimum value of the opening area of ​​the opening of the directional control valve communicating from the hydraulic pump to a hydraulic oil tank is limited. A shovel according to any one of claims 1 to 4.

8. The control valve control unit is when the failure determination unit determines that the regulator has failed, the failure determination unit limits a minimum value of an opening area of ​​an opening of the directional control valve communicating from the hydraulic pump to a hydraulic oil tank. A shovel according to any one of claims 1 to 4.

9. The hydraulic pump includes a first hydraulic pump and a second hydraulic pump. The directional control valve includes a first system directional control valve to which hydraulic oil is supplied from the first hydraulic pump, and a second system directional control valve to which hydraulic oil is supplied from the second hydraulic pump, The control valve control unit is When both the first system directional control valve and the second system directional control valve are operated, the directional control valve is controlled at a first upper limit; When only one of the directional control valve of the first system or the directional control valve of the second system is operated, the directional control valve is controlled at a second upper limit which is higher than the first upper limit. A shovel according to any one of claims 1 to 4.

10. Further, a solenoid proportional valve is provided for controlling a pilot pressure of the directional control valve. The control valve control unit controls the electromagnetic proportional valve to control the directional control valve. A shovel according to any one of claims 1 to 4.

11. A tilt control proportional valve for controlling the pilot pressure of the regulator is further provided. The control device further includes a regulator control unit that controls the tilt angle of the swash plate of the regulator by controlling the tilt control proportional valve, The regulator is configured such that, when the tilt control proportional valve is closed, the tilt angle is at a maximum tilt angle and the flow rate of the hydraulic oil discharged by the hydraulic pump is at a maximum. A shovel according to any one of claims 1 to 4.

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