JP7740643B2 - Excavator - Google Patents

Description

This disclosure relates to a shovel.

Patent Document 1 discloses an excavator having a lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, a driver's cab mounted on the upper rotating body, an attachment including a boom attached to the upper rotating body, a boom cylinder that drives the boom, a control device that controls hydraulic oil that can flow into the boom cylinder, and an information acquisition device that acquires information about the attachment, and the control device increases the pressure of the hydraulic oil that can flow into the boom cylinder in accordance with the information about the attachment before a boom-raising operation is performed.

International Publication No. 2018-164238

However, during combined operations in which the upper rotating body's rotation operation and attachment operations such as boom raising are performed simultaneously, the rotation speed of the upper rotating body's rotation operation relative to the amount of operation of the operating lever increases compared to when only the upper rotating body's rotation operation is performed. This could result in a decrease in the operability of the upper rotating body's rotation operation.

Therefore, the present invention aims to provide a shovel that improves operability.

An excavator according to an embodiment of the present invention comprises a lower traveling body, an upper rotating body that can rotate relative to the lower traveling body, a swing hydraulic motor that rotates the upper rotating body, a hydraulic pump that supplies hydraulic oil, a directional control valve that controls the supply of hydraulic oil from the hydraulic pump to the swing hydraulic motor, and a control unit that controls the directional control valve, and the control unit limits the pilot pressure of the directional control valve when the pump pressure of the hydraulic pump is equal to or higher than a predetermined pressure.

The present invention provides a shovel with improved operability.

FIG. 1 is a side view of a shovel according to an embodiment of the present invention. FIG. 2 is a top view of the shovel of FIG. 1 . FIG. 2 is a diagram showing an example of the configuration of a hydraulic system mounted on the excavator of FIG. 1 . FIG. 1 is a diagram of a portion of a hydraulic system for a swing hydraulic motor. 4 is a flowchart illustrating control of a proportional valve by a controller. 6 is a graph illustrating an increase limit of the pilot pressure of the control valve relative to the pump pressure of the main pump. 4 is a graph illustrating an example of a change in pilot pressure of a control valve.

First, with reference to Figures 1 and 2, a shovel 100 as an excavator according to an embodiment of the present invention will be described. Figure 1 is a side view of the shovel 100, and Figure 2 is a top view of the shovel 100.

In this embodiment, the undercarriage 1 of the excavator 100 includes a crawler 1C. The crawler 1C is driven by a traveling hydraulic motor 2M, which serves as a traveling actuator, mounted on the undercarriage 1. Specifically, the crawler 1C includes a left crawler 1CL and a right crawler 1CR. The left crawler 1CL is driven by a left traveling hydraulic motor 2ML, and the right crawler 1CR is driven by a right traveling hydraulic motor 2MR.

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, which serves as a rotating actuator, mounted on the upper rotating body 3. However, the rotating actuator may also be a rotating motor-generator, which serves as an electric actuator.

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 Figures 1 and 2, the bucket 6 is an excavation bucket, but it may also be a skeleton bucket or a gravel removal bucket. The bucket 6 may also be equipped with a bucket tilt mechanism.

The upper rotating body 3 is provided with a cabin 10 serving as a driver's cab, and is equipped with a power source such as an engine 11. Inside the cabin 10, an operating device 26, a controller 30, an operation method switching device SD, etc. are provided. The upper rotating body 3 is also equipped with a spatial recognition device 70, etc. For convenience, in this document, the side of the upper rotating body 3 where the attachment AT is attached will be referred to as the front, and the side where the counterweight is attached will be referred to as the rear.

The spatial recognition device 70 is configured to recognize objects present in the three-dimensional space around the shovel 100. The spatial recognition device 70 may also be configured to calculate the 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, millimeter-wave radar, an imaging device, 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 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 70R attached to the right end of the upper surface of the upper rotating body 3. An upward sensor that recognizes objects present in the space above the upper rotating body 3 may also be attached to the shovel 100.

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.

The operation mode switching device SD is configured to switch the operation mode of the control lever. For example, the operation mode switching device SD includes a push button switch provided on the right console inside the cabin 10, and is configured to switch the operation mode of the control lever between a first operation mode and a second operation mode each time the push button switch is pressed. For example, the first operation mode is configured so that when the left control lever 26L (see Figure 3) is tilted forward, the arm 5 is opened, when the left control lever 26L is tilted rearward, the arm 5 is closed, when the left control lever 26L is tilted left, a left turn is performed, and when the left control lever 26L is tilted right, a right turn is performed. The first operation method is configured so that when the right operating lever 26R (see FIG. 3) is tilted forward, the boom 4 is lowered, when the right operating lever 26R is tilted rearward, the boom 4 is raised, when the right operating lever 26R is tilted left, the bucket 6 is closed, and when the right operating lever 26R is tilted right, the bucket 6 is opened. On the other hand, the second operation method is configured so that when the left operating lever 26L (see FIG. 3) is tilted forward, a right turn is performed, when the left operating lever 26L is tilted rearward, a left turn is performed, when the left operating lever 26L is tilted left, the arm 5 is opened, and when the left operating lever 26L is tilted right, the arm 5 is closed.

The operator of the excavator 100 may, for example, select the first operating method when performing excavation work using an excavation bucket, and may select the second operating method when performing gravel removal work using a skeleton bucket (gravel removal bucket).

The controller 30 is a control device for controlling the shovel 100. In this embodiment, the controller 30 is configured as a computer equipped with a CPU, a volatile storage device, a non-volatile storage device, etc. The controller 30 reads programs corresponding to each function from the non-volatile storage device, loads them into the volatile storage device, and causes the CPU to execute the corresponding processing. 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 assists the operator in manually operating the shovel 100 or operates the shovel 100 automatically or autonomously. The controller 30 may also include a contact avoidance function that automatically or autonomously operates or stops the shovel 100 to avoid contact between the shovel 100 and objects 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.

Next, referring to Figure 3, an example configuration of a hydraulic system mounted on the excavator 100 will be described. Figure 3 is a diagram showing an example configuration of a hydraulic system mounted on the excavator 100. In Figure 3, the mechanical power transmission system, hydraulic oil lines, pilot lines, and electrical control system are indicated by double lines, solid lines, dashed lines, and dotted lines, respectively.

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 operating sensor 29, and a controller 30.

In Figure 3, the hydraulic system is configured to circulate hydraulic oil from the main pump 14 driven by the engine 11 to the hydraulic oil tank via the center bypass line 40 or parallel line 42.

The engine 11 is the driving 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. The output shaft of the engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15.

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

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

The pilot pump 15 is an example of a pilot pressure generating device and is configured 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 also be realized by the main pump 14. That is, the main pump 14 may have the function of supplying hydraulic oil to the control valve unit 17 via a hydraulic oil line, as well as the function of supplying hydraulic oil to various hydraulic control devices via a pilot line. In this case, the pilot pump 15 may be omitted.

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 171-176. Control valve 175 includes control valve 175L and control valve 175R, and control valve 176 includes control valve 176L and 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 via the control valves 171-176. The control valves 171-176 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 the 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.

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 to the pilot port of the corresponding control valve in the control valve unit 17 via a pilot line. The pressure of the hydraulic oil supplied to each pilot port (pilot pressure) is a pressure that corresponds to the direction and amount of operation of the operating device 26 corresponding to each hydraulic actuator.

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.

The operation sensor 29 is configured to detect the operation of the operation device 26 by the 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.

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 the hydraulic oil tank via the left center bypass line 40L or the left parallel line 42L, and the right main pump 14R circulates hydraulic oil to the hydraulic oil tank via the right center bypass line 40R or the right parallel line 42R.

The left center bypass line 40L is a hydraulic oil line that passes through control valves 171, 173, 175L, and 176L located within 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 located within the control valve unit 17.

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

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

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.

The control valve 174 is a spool valve that switches the flow of hydraulic oil to supply 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.

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. 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.

The control valve 176L is a spool valve that switches the flow of hydraulic oil to supply 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.

The control valve 176R is a spool valve that switches the flow of hydraulic oil to supply 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.

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 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 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.

The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L controls the discharge volume of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L in response 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, thereby reducing the discharge volume. The same is true for the right regulator 13R. This is to ensure that the absorption power (absorption horsepower) of the main pump 14, which is expressed as the product of the discharge pressure and the discharge volume, does not exceed the output power (output horsepower) of the engine 11.

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 travel lever 26DL and a right travel lever 26DR.

The left operating lever 26L is used for swing operations and operating the arm 5. When the left operating lever 26L is operated in the forward/backward direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce control pressure corresponding 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, it uses the hydraulic oil discharged from the pilot pump 15 to introduce control pressure corresponding to the amount of lever operation into the pilot port of the control valve 173.

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 into the left pilot port of the control valve 176R. Furthermore, 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 into the right pilot port of the control valve 176R. Furthermore, 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 operated in the right turning direction, it introduces hydraulic oil into the right pilot port of the control valve 173.

In the example shown in Figure 3, the left operating lever 26L functions as an arm operating lever when operated in the forward/backward direction, and functions as a rotation operating lever when operated in the left/right direction.

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 from the pilot pump 15 to introduce control pressure corresponding to the amount of lever operation into the pilot port of the control valve 175. When it is operated in the left/right direction, it uses the hydraulic oil discharged from the pilot pump 15 to introduce control pressure corresponding to the amount of lever operation into the pilot port of the control valve 174.

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

In the example shown in Figure 3, the right operating lever 26R functions as a boom operating lever when operated in the forward/backward direction, and functions as a bucket operating lever when operated in the left/right direction.

The travel lever 26D is used to operate the crawler 1C. Specifically, the left travel lever 26DL is used to operate the left crawler 1CL. It may be configured to operate in conjunction with the left travel pedal. When the left travel lever 26DL is operated in the forward/backward direction, it uses hydraulic oil discharged from the pilot pump 15 to introduce control pressure corresponding to the amount of lever operation into the pilot port of the control valve 171. The right travel lever 26DR is used to operate the right crawler 1CR. It may be configured to operate in conjunction with the right travel pedal. When the right travel lever 26DR is operated in the forward/backward direction, it uses hydraulic oil discharged from the pilot pump 15 to introduce control pressure corresponding to the amount of lever operation into the pilot port of the control valve 172.

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.

Operation sensor 29 includes operation sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. Operation sensor 29LA detects the operation of left operating lever 26L by the operator in the forward/backward direction, and outputs the detected value to controller 30. Examples of the operation include the lever operation direction and lever operation amount (lever operation angle).

Similarly, operation sensor 29LB detects the operation of the left control lever 26L in the left-right direction by the operator and outputs the detected value to controller 30. Operation sensor 29RA detects the operation of the right control lever 26R in the forward-backward direction by the operator and outputs the detected value to controller 30. Operation sensor 29RB detects the operation of the right control lever 26R in the left-right direction by the operator and outputs the detected value to controller 30. Operation sensor 29DL detects the operation of the left travel lever 26DL in the forward-backward direction by the operator and outputs the detected value to controller 30. Operation sensor 29DR detects the operation of the right travel lever 26DR in the forward-backward direction by the operator and outputs the detected value to controller 30.

The controller 30 receives the output of the operation sensor 29 and outputs a control command to the regulator 13 as necessary to change the discharge rate of the main pump 14. The controller 30 also receives the output of the control pressure sensor 19 located upstream of the orifice 18 and outputs a control command to the regulator 13 as necessary to change the discharge rate of the main pump 14. The orifice 18 includes a left orifice 18L and a right orifice 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R.

A left throttle 18L is located in the left center bypass line 40L between the hydraulic oil tank and the control valve 176L, which is located most downstream. Therefore, the flow of hydraulic oil discharged from the left main pump 14L is restricted by the left throttle 18L. The left throttle 18L then generates a control pressure to control the left regulator 13L. The left control pressure sensor 19L detects this control pressure and outputs the detected value to the controller 30. The controller 30 controls the discharge rate 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 rate of the left main pump 14L as this control pressure increases, and increases the discharge rate of the left main pump 14L as this control pressure decreases. The discharge rate of the right main pump 14R is controlled in a similar manner.

Specifically, as shown in FIG. 3 , when the excavator 100 is in a standby state in which none of the hydraulic actuators are operated, hydraulic oil discharged from the left main pump 14L passes through the left center bypass line 40L and reaches the left throttle 18L. The flow of hydraulic oil discharged from 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 rate of the left main pump 14L to the minimum allowable discharge rate, suppressing pressure loss (pumping loss) when the discharged hydraulic oil passes through the left center bypass line 40L. Meanwhile, when one of the hydraulic actuators is operated, hydraulic oil discharged from the left main pump 14L flows into the hydraulic actuator to be operated via the control valve corresponding to the hydraulic actuator. The flow of hydraulic oil discharged from the left main pump 14L reduces or eliminates the amount of hydraulic oil reaching the left throttle 18L, thereby 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, circulating sufficient hydraulic oil to the hydraulic actuator to be operated and ensuring reliable 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.

With the above-described configuration, the hydraulic system of FIG. 3 can reduce unnecessary energy consumption in the main pump 14 when in standby mode. This unnecessary energy consumption includes pumping loss caused by the hydraulic oil discharged by the main pump 14 in the center bypass line 40. Furthermore, when operating a hydraulic actuator, the hydraulic system of FIG. 3 can reliably supply sufficient hydraulic oil from the main pump 14 to the hydraulic actuator being operated.

Furthermore, 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, boom bottom pressure sensor S7B, arm rod pressure sensor S8R, arm bottom pressure sensor S8B, bucket rod pressure sensor S9R, and bucket bottom pressure sensor S9B are collectively referred to as "cylinder pressure sensors." Furthermore, a left swing pressure sensor S10L and a right swing pressure sensor S10R are attached to the swing hydraulic motor 2A.

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"), 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 "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"), 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 "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"), 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 "bucket bottom pressure"). The left swing pressure sensor S10L detects the pressure of hydraulic oil in the left port of the swing hydraulic motor 2A. The right swing pressure sensor S10R detects the pressure of hydraulic oil in the right port of the swing hydraulic motor 2A. The values detected by each sensor are sent to the controller 30.

Next, referring to Figure 4, we will explain the configuration in which the controller 30 operates the actuator using the machine control function. Figure 4 is a diagram of the hydraulic system portion related to the operation of the swing hydraulic motor 2A.

As shown in FIG. 4, the hydraulic system includes a proportional valve 31. The proportional valve 31 includes proportional valves 31DL and 31DR.

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 the pilot port of the corresponding control valve in the control valve unit 17, and is configured to be able to change the flow path area of that 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 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 operator's operation of the operating device 26. The controller 30 can then apply the pilot pressure generated by the proportional valve 31 to the pilot port of the corresponding control valve.

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.

For example, as shown in FIG. 4, the left operating lever 26L is also used to operate the swing mechanism 2. Specifically, the left operating lever 26L uses hydraulic oil discharged from the pilot pump 15 to apply pilot pressure corresponding to left/right operation to the pilot port of the control valve 173. More specifically, when the left operating lever 26L is operated in the left swing direction (leftward), it applies pilot pressure corresponding to the amount of operation to the left pilot port of the control valve 173. Furthermore, when the left operating lever 26L is operated in the right swing direction (rightward), it applies pilot pressure corresponding to the amount of operation to the right pilot port of the control valve 173.

The left operating lever 26L is provided with a switch NS (NSL). In this embodiment, the switch NS is a push button switch provided at the tip of the left operating lever 26L. The operator can operate the left operating lever 26L while pressing the switch NS. Alternatively, the right operating lever 26R may be provided with a switch NS (NSR), or the switch NS may be provided at another position within the cabin 10.

The operation sensor 29LB detects the left/right operation of the left operating lever 26L by the operator and outputs the detected value to the controller 30.

Proportional valve 31DL operates in response to a control command (current command) output by controller 30. It adjusts the pilot pressure of hydraulic oil introduced from pilot pump 15 via proportional valve 31DL to the left pilot port of control valve 173. Proportional valve 31DR operates in response to a control command (current command) output by controller 30. It adjusts the pilot pressure of hydraulic oil introduced from pilot pump 15 via proportional valve 31DR to the right pilot port of control valve 173. Proportional valve 31DL can adjust the pilot pressure so that control valve 173 can be stopped at any valve position. Similarly, proportional valve 31DR can adjust the pilot pressure so that control valve 173 can be stopped at any valve position.

A pilot pressure sensor 32DL that detects pilot pressure is provided in the pilot line connecting the proportional valve 31DL and one port of the control valve 173 (the left port of the control valve 173). A pilot pressure sensor 32DR that detects pilot pressure is provided in the pilot line connecting the proportional valve 31DR and the other port of the control valve 173 (the right port of the control valve 173). The values detected by each pilot pressure sensor 32DL, 32DR are sent to the controller 30.

With this configuration, the controller 30 can supply hydraulic oil discharged from the pilot pump 15 to the left pilot port of the control valve 173 via the proportional valve 31DL in response to a left rotation operation by the operator. Furthermore, the controller 30 can supply hydraulic oil discharged from the pilot pump 15 to the left pilot port of the control valve 173 via the proportional valve 31DL, regardless of a left rotation operation by the operator. In other words, the controller 30 can rotate the rotation mechanism 2 left in response to a left rotation operation by the operator, or regardless of a left rotation operation by the operator.

In addition, in response to a right turn operation by the operator, the controller 30 can supply hydraulic oil discharged from the pilot pump 15 to the right pilot port of the control valve 173 via the proportional valve 31DR. In addition, regardless of a right turn operation by the operator, the controller 30 can supply hydraulic oil discharged from the pilot pump 15 to the right pilot port of the control valve 173 via the proportional valve 31DR. In other words, the controller 30 can rotate the swing mechanism 2 to the right in response to a right turn operation by the operator, or regardless of a right turn operation by the operator.

Furthermore, with this configuration, even if the operator is performing a left turn operation, the controller 30 can, as necessary, reduce the pilot pressure acting on the left pilot port of the control valve 173 to forcibly stop the left turn operation. The same applies to forcibly stopping a right turn operation when the operator is performing a right turn operation.

Alternatively, even if the operator is performing a left turn operation, the controller 30 may, as necessary, control the proportional valve 31DR to increase the pilot pressure acting on the right pilot port of the control valve 173, which is located opposite the left pilot port of the control valve 173, and forcibly return the control valve 173 to the neutral position, thereby forcibly stopping the left turn operation. The same applies to the case where the left turn operation is being forcibly stopped when the operator is performing a left turn operation.

Note that while Figure 4 describes the hydraulic system portion related to the operation of the swing hydraulic motor 2A, the hydraulic system portion related to the operation of the boom cylinder 7, the hydraulic system portion related to the operation of the arm cylinder 8, the hydraulic system portion related to the operation of the bucket cylinder 9, 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 also be configured in a similar manner.

Although the description has been given of an electric control lever as the form of the operating device 26, a hydraulic control lever may be used instead. In this case, the lever operation amount of the hydraulic control lever may be detected in the form of pressure by a pressure sensor and input to the controller 30. Furthermore, a solenoid valve may be disposed between the operating device 26 as a hydraulic control lever and the pilot port of each control valve. The solenoid valve is configured to operate in response to an electrical signal from the controller 30. With this configuration, when manual operation is performed using the operating device 26 as a hydraulic control lever, the operating device 26 can move each control valve by increasing or decreasing the pilot pressure in response to the lever operation amount. Furthermore, each control valve may be configured as an electromagnetic spool valve. In this case, the electromagnetic spool valve operates in response to an electrical signal from the controller 30 that corresponds to the lever operation amount of the electric control lever.

As described above, the controller 30 receives the output of the operation sensor 29 and outputs a control command to the regulator 13 as necessary to change the discharge rate of the main pump 14. The controller 30 also receives the output of the control pressure sensor 19 located upstream of the throttle 18 and outputs a control command to the regulator 13 as necessary to change the discharge rate of the main pump 14.

For example, when excavating the ground at an angle relative to the fore-and-aft direction of the upper rotating body 3, a combined operation is performed in which the upper rotating body 3 is rotated and the attachment AT (boom 4, arm 5, bucket 6) is excavated at the same time.

During combined operations in which the upper rotating body 3 is rotated and an attachment operation such as a boom-raising operation is performed simultaneously, the discharge volume of the main pump 14 increases, and the discharge pressure (pump pressure) of the main pump 14 rises, compared to swing-only operations in which only the upper rotating body 3 is rotated. Furthermore, during combined operations involving swing and excavation operations, the load on the swing hydraulic motor 2A is smaller than the load on the boom cylinder 7, which operates the attachment AT. Therefore, the flow rate from the main pump 14 to the swing hydraulic motor 2A increases. As a result, during combined operations, the swing speed of the upper rotating body 3 relative to the amount of operation of the operating device 26 (the amount of operation of the left operating lever 26L in the left-right direction) may be greater than in swing-only operations.

Next, the control of the proportional valves 31 (31DL, 31DR) that control the control valve 173 will be further explained using Figure 5. Figure 5 is a flowchart explaining the control of the proportional valves 31 (31DL, 31DR) by the controller 30.

In step S101, the controller 30 determines whether a turning operation has been input. Here, the controller 30 determines whether a turning operation has been input based on the left/right operation of the left operating lever 26L by the operator detected by the operation sensor 29RB. If a turning operation has not been input (S101, NO), the controller 30 repeats the processing of step S101. If a turning operation has been input (S101, YES), the processing of the controller 30 proceeds to step S102.

In step S102, the controller 30 acquires the pump pressure of the main pump 14. Here, the controller 30 detects the pump pressure of the main pump 14 (14L, 14R) using the discharge pressure sensors 28 (28L, 28R).

In step S103, the controller 30 determines the increase limit of the pilot pressure of the control valve 173 based on the pump pressure of the main pump 14 obtained in step S102.

The increase limit of the pilot pressure of the control valve 173 determined in step S102 will be explained using Figure 6. Figure 6 is a graph explaining the increase limit of the pilot pressure of the control valve 173 relative to the pump pressure of the main pump 14.

Figure 6(a) is a graph illustrating an example of the increase limit of the pilot pressure of the control valve 173 relative to the pump pressure of the main pump 14. The horizontal axis represents the pump pressure (MPa) of the main pump 14. The vertical axis represents the increase limit of the pilot pressure (hereinafter also referred to as the "swing Pi pressure increase limit") (MPa/ms) in the control valve 173 that controls the swing hydraulic motor 2A. In the example of Figure 6(a), the increase rate of the pilot pressure in the control valve 173 that controls the swing hydraulic motor 2A is limited to a maximum value.

In the example of FIG. 6(a), when the pump pressure of the main pump 14 is equal to or less than the first pressure value P1, the swing Pi pressure increase limit is set to a predetermined first limit value B1. Furthermore, when the pump pressure of the main pump 14 is equal to or greater than the first pressure value P1 (equal to or less than the second pressure value P2), the swing Pi pressure increase limit is set to decrease as the pump pressure of the main pump 14 increases. Furthermore, when the pump pressure of the main pump 14 is equal to or greater than the second pressure value P2, which is greater than the first pressure value P1, the swing Pi pressure increase limit is set to a second limit value B2, which is smaller than the first limit value B1. For example, if the pump pressure of the main pump 14 acquired in step S102 is pressure value P3, the swing Pi pressure increase limit is determined to be limit value B3.

Note that limiting the increase in pilot pressure of the control valve 173 is not limited to limiting the rate of increase in pilot pressure of the control valve 173 as shown in Figure 6(a).

Figure 6(b) is a graph illustrating another example of the increase limit of the pilot pressure of the control valve 173 relative to the pump pressure of the main pump 14. The horizontal axis represents the pump pressure (MPa) of the main pump 14. The vertical axis represents the increase limit (hereinafter also referred to as the "increase limit rate") of the pilot pressure in the control valve 173 that controls the swing hydraulic motor 2A. In the example of Figure 6(b), the increase rate of the pilot pressure in the control valve 173 that controls the swing hydraulic motor 2A is limited by a rate.

6(b), when the pump pressure of the main pump 14 is equal to or less than the first pressure value P4, the increase restriction rate is set to a predetermined first restriction rate value C4. Here, the first restriction rate value C4 may be set to 1. Furthermore, when the pump pressure of the main pump 14 is equal to or greater than the first pressure value P4 (equal to or less than the second pressure value P5), the increase restriction rate is set to decrease as the pump pressure of the main pump 14 increases. Furthermore, when the pump pressure of the main pump 14 is equal to or greater than the second pressure value P5, which is greater than the first pressure value P4, the increase restriction rate is set to a second restriction rate value C5, which is smaller than the first restriction rate value C4. For example, when the pump pressure of the main pump 14 acquired in step S102 is pressure value P6, the increase restriction rate is determined to be restriction rate value C6. When the pump pressure of the main pump 14 acquired in step S102 is pressure value P7, the increase restriction rate is determined to be restriction rate value C7.

In step S104, the controller 30 checks the increase in pilot pressure of the control valve 173 based on the operator's operation of the left operating lever 26L. Specifically, the controller 30 calculates the increase in pilot pressure per unit time (increase rate) of the control valve 173 when controlling the proportional valve 31 (31DL, 31DR) based on the operation amount detected by the operation sensor 29RB.

In step S105, the controller 30 determines whether the increase value (increase rate) of the pilot pressure of the control valve 173 calculated in step S104 is equal to or greater than the increase limit determined in step S103.

Here, in the increase limit shown in the example of Figure 6(a), if the increase value (increase rate) of the pilot pressure is equal to or greater than the increase limit (S105, YES), the processing of the controller 30 proceeds to step S106. On the other hand, if the increase value (increase rate) of the pilot pressure is not equal to or greater than the increase limit (S105, NO), the processing of the controller 30 proceeds to step S107.

Furthermore, in the case of the increase restriction shown in the example of Figure 6(b), the processing of the controller 30 proceeds to step S106.

In step S106, the controller 30 determines the increase value (increase rate) of the corrected pilot pressure in accordance with the increase limit.

Here, in the example of Figure 6(a), at pump pressure P1 of the main pump 14, the increase value (increase rate) of the corrected pilot pressure is determined as the swing Pi pressure increase limit B1.

Here, in the example of Figure 6(b), for pump pressure P2 of the main pump 14, the increase value (increase rate) of the corrected pilot pressure is determined as the increase value (increase rate) of the pilot pressure calculated in step S104 multiplied by coefficient C2. Also, for pump pressure P3 of the main pump 14, the increase value (increase rate) of the corrected pilot pressure is determined as the increase value (increase rate) of the pilot pressure calculated in step S104 multiplied by coefficient C3.

In step S107, the controller 30 calculates the output value to the proportional valve 31 (31DL, 31DR). Here, if the increase value (increase rate) of the pilot pressure is equal to or greater than the increase limit (S105, YES), the controller 30 calculates the output value of the proportional valve 31 based on the increase value (increase rate) of the corrected pilot pressure determined in step S106. On the other hand, if the increase value (increase rate) of the pilot pressure is not equal to or greater than the increase limit (S104, 5O), the controller 30 calculates the output value of the proportional valve 31 based on the increase value of the pilot pressure calculated in step S104.

In step S108, the controller 30 outputs the output value calculated in step S107 to the proportional valve 31. The processing of the controller 30 then returns to step S101.

Here, during swing-only operation, the pump pressure of the main pump 14 is assumed to be equal to or less than the first pressure value P1 (P4). When the pump pressure of the main pump 14 is less than the first pressure value P1 (P4), the controller 30 controls the control valve 173 via the proportional valve 31 based on the left/right operation of the left operating lever 26L detected by the operation sensor 29RB. In other words, no restrictions are imposed on the control of the control valve 173. Note that in FIG. 6(a), the first limit value B1 is a value sufficiently large relative to the increase value (increase rate) of the pilot pressure of the control valve 173, indicating that no restrictions are imposed on the control of the control valve 173. Also, in FIG. 6(b), the first limit percentage value C4 is, for example, 1, which, when multiplied by the increase value (increase rate) of the pilot pressure, is equal to the increase value (increase rate) of the pilot pressure, indicating that no restrictions are imposed on the control of the control valve 173.

Furthermore, during combined operation, the pump pressure of the main pump 14 is assumed to be equal to or greater than the first pressure value P1 (P4). When the pump pressure of the main pump 14 is equal to or greater than the first pressure value P1 (P4), the controller 30 places restrictions on the control of the control valve 173. Specifically, the controller 30 limits the increase value (increase rate) of the pilot pressure of the control valve 173. Therefore, even if the pump pressure of the main pump 14 increases, the movement speed of the spool of the control valve 173 is limited and moves slowly, thereby suppressing the rotation speed of the upper rotating body 3 and improving operability for the operator.

In step S102, the controller 30 may acquire the pump pressure of the main pump 14 and detect the swing load pressure of the swing hydraulic motor 2A. The swing load pressure of the swing hydraulic motor 2A may be calculated based on the differential pressure between the hydraulic oil pressure at the left port of the swing hydraulic motor 2A detected by the left swing pressure sensor S10L and the hydraulic oil pressure at the right port of the swing hydraulic motor 2A detected by the right swing pressure sensor S10R. The controller 30 may also use the swing load pressure together with the pump pressure to determine whether swing operation is alone or combined operation is occurring. The controller 30 may also determine whether swing operation is alone or combined operation is occurring based on the operation of the operating device 26 detected by the operation sensor 29.

Figure 7 is a graph illustrating an example of changes in the pilot pressure of the control valve 173. The horizontal axis represents time, and the vertical axis represents the pilot pressure of the control valve 173. Furthermore, the pilot pressure 700, shown by a solid line, represents changes in the pilot pressure of the control valve 173 when the proportional valve 31 is controlled based on the left/right operation of the left operating lever 26L detected by the operation sensor 29RB. The pilot pressure 701, shown by a dashed line, represents changes in the pilot pressure of the control valve 173 when limited by the swing Pi pressure increase limit B1 shown in Figure 6(a). The pilot pressure 702, shown by a dashed line, represents changes in the pilot pressure of the control valve 173 when limited by the increase limit rate C2 shown in Figure 6(b). The pilot pressure 702, shown by a dotted line, represents changes in the pilot pressure of the control valve 173 when limited by the increase limit rate C3 shown in Figure 6(b).

During combined operation, the rate at which the pilot pressure of the control valve 173 increases is limited, as shown by pilot pressures 701-703 in Figure 7. This limits the movement speed of the spool of the control valve 173, causing it to move slowly, thereby suppressing the rotation speed of the upper rotating body 3 and improving operability for the operator.

Furthermore, as shown by pilot pressure 701 in Figure 7, the maximum rate of increase in pilot pressure is limited by the swing Pi pressure increase limit (see Figure 6(a)). This improves operability for the operator even during combined operations in which the pump pressure of the main pump 14 increases.

Furthermore, as shown by pilot pressures 702 and 703 in Figure 7, by limiting the increase limit rate (see Figure 6(b)), the rate at which the pilot pressure of the control valve 173 increases can be changed depending on the left/right operation state of the left operating lever 26L. This improves operability for the operator.

100 Excavator 1 Lower traveling body 2A Swing hydraulic motor (hydraulic actuator)
2M Travel hydraulic motor (hydraulic actuator)
2ML Left travel hydraulic motor (hydraulic actuator)
2MR Right 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)
14 Main pump (hydraulic pump)
17 Control valve units 171 to 176 Control valves (directional control valves)
19 Control pressure sensor 26 Operation device (electric lever)
28 Discharge pressure sensor 29 Operation sensor 30 Controller (control unit)
31 Proportional valve 32 Pilot pressure sensor

Claims (6)

a lower running body;
an upper rotating body that can rotate relative to the lower traveling body;
a hydraulic swing motor for swinging the upper swing body;
a hydraulic pump for supplying hydraulic oil;
a directional control valve for controlling the supply of hydraulic oil from the hydraulic pump to the swing hydraulic motor;
a control unit that controls the directional control valve,
The control unit
When the pump pressure of the hydraulic pump is equal to or higher than a predetermined pressure, a restriction is imposed on the pilot pressure of the directional control valve.
Shovel. an electric lever operated by an operator;
The control unit receives an operation amount of the electric lever.
The shovel according to claim 1. The restriction on the pilot pressure restricts the rate at which the pilot pressure increases.
The shovel according to claim 1 or 2. The restriction on the pilot pressure increases as the pump pressure increases.
The shovel according to claim 1 or 2. The restriction on the pilot pressure is executed during a combined operation including a rotation operation for rotating the upper rotating body.
The shovel according to claim 1 or 2. The restriction on the pilot pressure restricts the pilot pressure by a percentage.
The shovel according to claim 1 or 2.