Shovel

Abstract

A shovel (100) comprises a lower traveling body (1), an upper turning body (3) that is turnably mounted on the lower traveling body (1), an engine (11) that is mounted on the upper turning body (3), a main pump (14) that is driven by the engine (11), and a controller (30) that controls the flow rate of a hydraulic fluid discharged by the main pump (14). The controller (30) delays main pump (14) responsiveness until the actual torque of the engine (11) rises to a level corresponding to the load when the load on the engine (11) has been increased.

Description

Technical Field

[0001] The present disclosure relates to an excavator, specifically a shovel.

Background Art

[0002] Conventionally, there is a known shovel that controls the discharge amount of a hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the rated torque of the engine even when the discharge pressure of the hydraulic pump changes (see Patent Document 1).

[0003] The actual torque of an engine rotating at a predetermined rotational speed transitions at a level lower than the rated torque when the engine load is small. And the actual torque increases due to an increase in the fuel injection amount when the engine load increases and reaches the rated torque. Thus, the actual torque changes dynamically and rises with a certain delay when the engine load increases.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the control in the above-mentioned shovel does not consider the delay regarding the rise of the actual torque of the engine. Therefore, in the control in the above-mentioned shovel, there is a possibility that the absorption torque of the hydraulic pump temporarily exceeds the actual torque of the engine, resulting in a decrease in the engine rotational speed.

[0006] Therefore, it is desired to more reliably prevent the absorption torque of the hydraulic pump from exceeding the actual torque of the engine.

Means for Solving the Problems

[0007] An embodiment of the present invention comprises a lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, an engine mounted on the upper rotating body, a boost pressure sensor for detecting the boost pressure of a supercharger provided in the engine, a hydraulic pump driven by the engine, and a control device for controlling the flow rate of the hydraulic fluid discharged by the hydraulic pump, wherein the control device The required flow rate of the hydraulic pump is calculated based on at least one of the control pressure detected by the control pressure sensor, which functions as a negative control pressure sensor, the discharge pressure of the hydraulic pump detected by the discharge pressure sensor, and the operating pressure detected by the operating pressure sensor. before Summary The system calculates the required torque necessary to achieve the desired flow rate, and even before the engine load increases, it calculates a torque limit value that limits the required torque according to the boost pressure detected by the boost pressure sensor. Based on the torque limit value, it controls the hydraulic pump to delay the responsiveness of the hydraulic pump until the actual torque of the engine rises to a level corresponding to the engine load when the engine load increases. [Effects of the Invention]

[0008] The above means provide an excavator that can more reliably prevent the absorbed torque of the hydraulic pump from exceeding the actual torque of the engine. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of an excavator according to an embodiment of the present invention. [Figure 2] This diagram shows an example of a hydraulic system configuration installed in an excavator. [Figure 3] This figure shows an example of a controller configuration. [Figure 4] This shows an example of the temporal changes in values ​​related to the fluctuation suppression process when the boom is raised. [Figure 5] This shows another example of the temporal changes in values ​​related to the fluctuation suppression process when a boom raising operation is performed. [Modes for carrying out the invention]

[0010] First, with reference to Figure 1, 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. In this embodiment, an upper rotating body 3 is rotatably mounted on the lower traveling body 1 via a slewing mechanism 2. The lower traveling body 1 is driven by a traveling hydraulic motor 2M. The traveling hydraulic motor 2M includes a left traveling hydraulic motor 2ML that drives the left crawler, and a right traveling hydraulic motor 2MR (not visible in Figure 1) that drives the right crawler. The slewing mechanism 2 is driven by a slewing hydraulic motor 2A mounted on the upper rotating body 3. However, the slewing hydraulic motor 2A may be a slewing motor generator as an electric actuator.

[0011] 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, which serves as an end attachment, is attached to the tip of the arm 5. The boom 4, arm 5, and bucket 6 constitute an excavation attachment, 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.

[0012] The upper slewing body 3 is equipped with a cabin 10 that serves as the operator's cab, and is also fitted with a power source such as an engine 11. A controller 30 is also attached to the upper slewing body 3. For convenience, in this document, the side of the upper slewing body 3 to which the boom 4 is attached is referred to as the front, and the side to which the counterweight is attached is referred to as the rear.

[0013] The controller 30 is a control device for controlling the shovel 100. In this embodiment, the controller 30 is composed of a computer equipped with a CPU, a volatile memory device, and a non-volatile memory device. The controller 30 is configured to realize various functions by reading programs corresponding to various functional elements from the non-volatile memory device, loading them into a volatile memory device such as RAM, and having the CPU execute the corresponding processing.

[0014] Next, with reference to Figure 2, an example of the configuration of the hydraulic system installed in the excavator 100 will be described. Figure 2 shows an example of the configuration of the hydraulic system installed in the excavator 100. In Figure 2, the mechanical power transmission system, hydraulic fluid lines, pilot lines, and electrical control system are shown with double lines, solid lines, dashed lines, and dotted lines, respectively.

[0015] The hydraulic system of the Shovel 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operating device 26, a discharge pressure sensor 28, an operating pressure sensor 29, a controller 30, and an engine speed adjustment dial 75, etc.

[0016] In Figure 2, the hydraulic system circulates hydraulic fluid from the main pump 14, driven by the engine 11, through at least one of the center bypass pipeline 40 and the parallel pipeline 42 to the hydraulic fluid tank.

[0017] Engine 11 is the power source for the shovel 100. In this embodiment, engine 11 is, for example, a diesel engine that operates to maintain a predetermined rotational speed. The output shaft of engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15, respectively. Engine 11 is equipped with a supercharger. In this embodiment, the supercharger is a turbocharger. Engine 11 is controlled by an engine control unit. The engine control unit is configured, for example, to adjust the fuel injection amount in accordance with the boost pressure. The boost pressure is detected, for example, by a boost pressure sensor.

[0018] The main pump 14 is configured to supply hydraulic fluid to the control valve 17 via a hydraulic fluid line. In this embodiment, the main pump 14 is an electrically controlled hydraulic pump. Specifically, the main pump 14 is a swashplate type variable displacement hydraulic pump.

[0019] The regulator 13 controls the discharge volume of the main pump 14. In this embodiment, the regulator 13 controls the discharge volume 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, thereby controlling the displaced volume per revolution of the main pump 14.

[0020] The pilot pump 15 is configured to supply hydraulic fluid to the hydraulic control equipment, including the operating device 26, via a pilot line. In this embodiment, the pilot pump 15 is a fixed-displacement hydraulic pump. The pilot pump 15 may be omitted. In this case, the function that the pilot pump 15 performed may be realized by the main pump 14. That is, the main pump 14 may have a function to supply hydraulic fluid to the operating device 26, etc., after reducing the pressure of the hydraulic fluid by throttling or the like, in addition to the function of supplying hydraulic fluid to the control valve 17.

[0021] The control valve 17 is a hydraulic control device that controls the hydraulic system in the excavator 100. In this embodiment, the control valve 17 includes control valves 171 to 176, as shown by the dashed line. Control valve 175 includes control valves 175L and 175R, and control valve 176 includes control valves 176L and 176R. The control valve 17 can selectively supply hydraulic fluid discharged by the main pump 14 to one or more hydraulic actuators through control valves 171 to 176. Control valves 171 to 176 control the flow rate of hydraulic fluid flowing from the main pump 14 to the hydraulic actuators, and the flow rate of hydraulic fluid flowing from the hydraulic actuators to the hydraulic fluid tank. The hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left-travel hydraulic motor 2ML, a right-travel hydraulic motor 2MR, and a slewing hydraulic motor 2A.

[0022] The operating device 26 is a device used by an operator to operate the actuator. The actuator includes at least one of a hydraulic actuator and an electric actuator. In this embodiment, the operating device 26 supplies hydraulic fluid discharged by the pilot pump 15 to the pilot port of the corresponding control valve in the control valve 17 via a pilot line. The pilot pressure, which is the pressure of the hydraulic fluid supplied to each pilot port, is a pressure corresponding to the operating direction and amount of the lever or pedal (not shown) of the operating device 26 corresponding to each hydraulic actuator.

[0023] 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.

[0024] The operating pressure sensor 29 is configured to detect the content of an operation performed via the operating device 26. In this embodiment, the operating pressure sensor 29 detects the operating direction and amount of a lever or pedal, which is the operating device 26 corresponding to each actuator, in the form of pressure (operating pressure), and outputs the detected value to the controller 30. The content of the operation of the operating device 26 may be detected using a sensor other than the operating pressure sensor.

[0025] The main pump 14 includes a left main pump 14L and a right main pump 14R. The left main pump 14L circulates the hydraulic fluid to the hydraulic fluid tank via the left center bypass pipeline 40L or the left parallel pipeline 42L, while the right main pump 14R circulates the hydraulic fluid to the hydraulic fluid tank via the right center bypass pipeline 40R or the right parallel pipeline 42R.

[0026] The left center bypass pipeline 40L is a hydraulic fluid line that passes through control valves 171, 173, 175L, and 176L located within the control valve 17. The right center bypass pipeline 40R is a hydraulic fluid line that passes through control valves 172, 174, 175R, and 176R located within the control valve 17.

[0027] The control valve 171 is a spool valve that switches the flow of hydraulic fluid to supply the hydraulic fluid discharged by the left main pump 14L to the left travel hydraulic motor 2ML, and to discharge the hydraulic fluid discharged by the left travel hydraulic motor 2ML to the hydraulic fluid tank.

[0028] The control valve 172 is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the right travel hydraulic motor 2MR, and also switches the flow of hydraulic fluid to discharge the hydraulic fluid discharged by the right travel hydraulic motor 2MR to the hydraulic fluid tank.

[0029] The control valve 173 is a spool valve that supplies the hydraulic fluid discharged by the left main pump 14L to the swing hydraulic motor 2A, and also switches the flow of hydraulic fluid to discharge the hydraulic fluid discharged by the swing hydraulic motor 2A to the hydraulic fluid tank.

[0030] The control valve 174 is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the bucket cylinder 9 and switches the flow of the hydraulic fluid in order to discharge the hydraulic fluid in the bucket cylinder 9 to the hydraulic fluid tank.

[0031] Control valve 175L is a spool valve that switches the flow of hydraulic fluid to supply the hydraulic fluid discharged by the left main pump 14L to the boom cylinder 7. Control valve 175R is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the boom cylinder 7 and also switches the flow of hydraulic fluid to discharge the hydraulic fluid inside the boom cylinder 7 to the hydraulic fluid tank.

[0032] Control valve 176L is a spool valve that supplies the hydraulic fluid discharged by the left main pump 14L to the arm cylinder 8 and switches the flow of hydraulic fluid to discharge the hydraulic fluid in the arm cylinder 8 to the hydraulic fluid tank. Control valve 176R is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the arm cylinder 8 and switches the flow of hydraulic fluid to discharge the hydraulic fluid in the arm cylinder 8 to the hydraulic fluid tank.

[0033] The left parallel pipeline 42L is a hydraulic fluid line running parallel to the left center bypass pipeline 40L. The left parallel pipeline 42L can supply hydraulic fluid to a control valve further downstream if the flow of hydraulic fluid through the left center bypass pipeline 40L is restricted or blocked by any of the control valves 171, 173, and 175L. The right parallel pipeline 42R is a hydraulic fluid line running parallel to the right center bypass pipeline 40R. The right parallel pipeline 42R can supply hydraulic fluid to a control valve further downstream if the flow of hydraulic fluid through the right center bypass pipeline 40R is restricted or blocked by any of the control valves 172, 174, and 175R.

[0034] The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L is configured to control the discharge amount of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L in accordance with the discharge pressure of the left main pump 14L. This control is referred to as power control or horsepower control. Specifically, the left regulator 13L reduces the discharge amount by reducing the displaced volume per revolution by adjusting the swash plate tilt angle of the left main pump 14L in accordance with an increase in the discharge pressure of the left main pump 14L. The same applies to the right regulator 13R. This is to ensure that the absorption power of the main pump 14 (e.g., absorption horsepower), which is expressed as the product of the discharge pressure and the discharge amount, does not exceed the output power of the engine 11 (e.g., output horsepower).

[0035] 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.

[0036] The left operating lever 26L is used for slewing and operating the arm 5. When the left operating lever 26L is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce pilot pressure corresponding to the lever operation amount into the pilot port of the control valve 176. When it is operated in the left / right direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce pilot pressure corresponding to the lever operation amount into the pilot port of the control valve 173.

[0037] Specifically, when the left operating lever 26L is operated in the arm closing direction, it introduces hydraulic fluid into the right pilot port of control valve 176L and into the left pilot port of control valve 176R. When the left operating lever 26L is operated in the arm opening direction, it introduces hydraulic fluid into the left pilot port of control valve 176L and into the right pilot port of control valve 176R. Furthermore, when the left operating lever 26L is operated in the left rotation direction, it introduces hydraulic fluid into the left pilot port of control valve 173, and when operated in the right rotation direction, it introduces hydraulic fluid into the right pilot port of control valve 173.

[0038] 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 fluid discharged by the pilot pump 15 to introduce a pilot pressure corresponding to the lever operation amount into the pilot port of the control valve 175. When it is operated in the left / right direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a pilot pressure corresponding to the lever operation amount into the pilot port of the control valve 174.

[0039] Specifically, when the right operating lever 26R is operated in the boom lowering direction, it introduces hydraulic fluid into the right pilot port of the control valve 175R. When the right operating lever 26R is operated in the boom raising direction, it introduces hydraulic fluid into the right pilot port of the control valve 175L and also into the left pilot port of the control valve 175R. Furthermore, when the right operating lever 26R is operated in the bucket closing direction, it introduces hydraulic fluid into the left pilot port of the control valve 174, and when it is operated in the bucket opening direction, it introduces hydraulic fluid into the right pilot port of the control valve 174.

[0040] The travel lever 26D is used to operate the crawler. Specifically, the left travel lever 26DL is used to operate the left crawler. The left travel lever 26DL may be configured to be linked with the left travel pedal. When the left travel lever 26DL is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a pilot 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. The right travel lever 26DR may be configured to be linked with the right travel pedal. When the right travel lever 26DR is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a pilot pressure corresponding to the lever operation amount into the pilot port of the control valve 172.

[0041] The discharge pressure sensor 28 includes discharge pressure sensor 28L and discharge pressure sensor 28R. 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 discharge pressure sensor 28R.

[0042] The operating pressure sensor 29 includes operating pressure sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. The operating pressure sensor 29LA detects the nature of forward and backward operation of the left operating lever 26L in the form of pressure and outputs the detected value to the controller 30. The operation nature is, for example, the direction of lever operation and the amount of lever operation (lever operation angle).

[0043] Similarly, the operating pressure sensor 29LB detects the operation of the left operating lever 26L in the left-right direction as pressure and outputs the detected value to the controller 30. The operating pressure sensor 29RA detects the operation of the right operating lever 26R in the forward-backward direction as pressure and outputs the detected value to the controller 30. The operating pressure sensor 29RB detects the operation of the right operating lever 26R in the left-right direction as pressure and outputs the detected value to the controller 30. The operating pressure sensor 29DL detects the operation of the left travel lever 26DL in the forward-backward direction as pressure and outputs the detected value to the controller 30. The operating pressure sensor 29DR detects the operation of the right travel lever 26DR in the forward-backward direction as pressure and outputs the detected value to the controller 30.

[0044] The controller 30 may receive the output of the operating pressure sensor 29 and, if necessary, output a control command to the regulator 13 to change the discharge rate of the main pump 14.

[0045] Furthermore, the controller 30 is configured to perform negative control as energy-saving control using the aperture 18 and the control pressure sensor 19. The aperture 18 includes a left aperture 18L and a right aperture 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R. In this embodiment, the control pressure sensor 19 functions as a negative control pressure sensor. Energy-saving control is a control that reduces the discharge amount of the main pump 14 in order to suppress unnecessary energy consumption by the main pump 14.

[0046] In the left center bypass pipeline 40L, a left throttle 18L is located between the control valve 176L, which is the furthest downstream, and the hydraulic fluid tank. Therefore, the flow of hydraulic fluid discharged by the left main pump 14L is restricted by the left throttle 18L. The left throttle 18L generates a control pressure (negative control pressure) to control 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 negative control by adjusting the swash plate tilt angle of the left main pump 14L in accordance with this control pressure. The controller 30 decreases the discharge amount of the left main pump 14L when this control pressure is high, and increases the discharge amount of the left main pump 14L when this control pressure is low. The discharge amount of the right main pump 14R is controlled in the same way.

[0047] Specifically, as shown in Figure 2, when none of the hydraulic actuators in the shovel 100 are operated, i.e., when the shovel 100 is in standby mode, the hydraulic fluid discharged by the left main pump 14L flows through the left center bypass pipe 40L to the left constrictor 18L. The flow of hydraulic fluid discharged by the left main pump 14L increases the control pressure generated upstream of the left constrictor 18L. As a result, the controller 30 reduces the discharge amount of the left main pump 14L to the standby flow rate, suppressing pressure loss (pumping loss) as the discharged hydraulic fluid passes through the left center bypass pipe 40L. The standby flow rate is a predetermined flow rate adopted when in standby mode, for example, the minimum allowable discharge amount. On the other hand, when any of the hydraulic actuators are operated, the hydraulic fluid discharged by the left main pump 14L flows into the hydraulic actuator being operated via the control valve corresponding to the hydraulic actuator being operated. The control valve corresponding to the hydraulic actuator being operated reduces or eliminates the flow rate of hydraulic fluid up to 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 volume of the left main pump 14L, ensuring sufficient hydraulic fluid circulation to the hydraulic actuator being operated and guaranteeing reliable operation of the hydraulic actuator. The controller 30 also controls the discharge volume of the right main pump 14R in the same manner.

[0048] Through the negative control described above, the hydraulic system in Figure 2 can suppress unnecessary energy consumption in the main pump 14 when in standby mode. Unnecessary energy consumption includes pumping losses caused by the hydraulic fluid discharged by the main pump 14 in the center bypass pipeline 40. Furthermore, when operating a hydraulic actuator, the hydraulic system in Figure 2 can reliably supply the necessary and sufficient hydraulic fluid from the main pump 14 to the hydraulic actuator being operated.

[0049] The engine speed adjustment dial 75 is a dial for adjusting the rotational speed of the engine 11. The engine speed adjustment dial 75 transmits data indicating the set state of the engine speed to the controller 30. In this embodiment, the engine speed adjustment dial 75 is configured to switch the engine speed in four stages: SP mode, H mode, A mode, and IDLE mode. SP mode is the rotational speed mode selected when prioritizing work volume, and uses the highest engine speed. H mode is the rotational speed mode selected when balancing work volume and fuel efficiency, and uses the second highest engine speed. A mode is the rotational speed mode selected when prioritizing fuel efficiency and operating the shovel 100 with low noise, and uses the third highest engine speed. IDLE mode is the rotational speed mode selected when the engine 11 is to be idled, and uses the lowest engine speed. The engine 11 is controlled to rotate at a constant speed according to the rotational speed mode set by the engine speed adjustment dial 75.

[0050] Next, referring to Figure 3, we will explain the process of suppressing fluctuations in the flow rate command value Q output by the controller 30 to the regulator 13 (hereinafter referred to as the "fluctuation suppression process"). Figure 3 is a diagram showing an example of the configuration of the controller 30.

[0051] In this embodiment, the controller 30 includes a requested torque calculation unit E1, a torque limiting unit E2, a fluctuation suppression unit E3, and a flow rate command calculation unit E4. The controller 30 then calculates the requested flow rate Q at predetermined control cycles. * , discharge pressure P, and boost pressure P B It accepts the following as input, and the torque limit value T" limit It is also configured to output the flow rate command value Q, etc.

[0052] Required flow rate Q *is a value calculated as the flow rate of the hydraulic oil to be discharged by the main pump 14. The controller 30 calculates, for example, the required flow rate Q based on at least one of the control pressure detected by the control pressure sensor 19, the discharge pressure detected by the discharge pressure sensor 28, and the operating pressure detected by the operating pressure sensor 29. * The required flow rate Q * may be calculated by the control pressure sensor 19. In this case, the control pressure sensor 19 outputs the required flow rate Q * to the controller 30. In the present embodiment, the controller 30 calculates the required flow rate Q * based on the control pressure detected by the control pressure sensor 19.

[0053] The required torque calculation unit E1 is configured to calculate the required torque T <所定のトルク算出部>The required torque T * is a value calculated as the torque required to achieve the required flow rate Q * In the present embodiment, the required torque calculation unit E1 receives the required flow rate Q * and the discharge pressure P as inputs, and calculates the required torque T * using Equation (1).

[0054]

Equation

[0055]

number

[0056] The flow rate command calculation unit E4 is configured to calculate the flow rate command value Q to be output to the regulator 13. In this embodiment, the flow rate command calculation unit E4 calculates the discharge pressure P detected by the discharge pressure sensor 28 and the torque limit value T calculated by the fluctuation suppression unit E3. limit The system takes the inputs and calculates the flow rate command value Q using equation (3).

[0057]

number

[0058] Next, the effect of the fluctuation suppression treatment will be explained with reference to Figure 4. Figure 4 shows the temporal changes in values ​​related to the fluctuation suppression treatment when the boom raising operation is performed. Specifically, Figure 4 includes Figure 4(A) and Figure 4(B). Figure 4(A) shows the temporal changes in values ​​related to torque. The values ​​related to torque are the allowable torque T limit and torque limit value T" limit This includes [the following]. Figure 4(B) shows the time course of engine speed.

[0059] More specifically, the dashed line in Figure 4(A) represents the allowable torque T that the torque limiting unit E2 derives at predetermined control cycles. limit This shows the temporal progression. The solid line in Figure 4(A) represents the torque limit value T" that the fluctuation suppression unit E3 derives at predetermined control cycles. limit This shows the temporal progression. The dashed line in Figure 4(B) represents the case where the fluctuation suppression unit E3 is absent, i.e., the torque limit value T" limit Instead of allowable torque T limit This shows the temporal change in engine speed when the flow rate command calculation unit E4 receives input. The solid line in Figure 4(B) represents the case when the fluctuation suppression unit E3 is present, i.e., when the torque limit value T" is present. limitThis shows the temporal change in engine speed when the flow rate command calculation unit E4 receives input.

[0060] From time t0 to time t1, no hydraulic load is applied to the engine 11 due to work. Even during this period, the controller 30 controls the required flow rate Q using the torque limiting unit E2 and the fluctuation suppression unit E3. * The output state of the engine 11 based on the discharge pressure P (torque limit value T) limit The controller 30 estimates the torque limit value T" of the main pump 14, and the flow rate command calculation unit E4 calculates the flow rate command value Q corresponding to the output state of the engine 11. Therefore, even before the load on the engine 11 increases, the controller 30 delays the response of the main pump 14 by setting a torque limit value T" limit The controller 30 calculates a flow command value Q that delays the response of the main pump 14.

[0061] Therefore, when no heavy load is applied, the controller 30 can reduce the engine output by calculating a small flow command value Q.

[0062] At time t1, when the right operating lever 26R is operated in the boom-raising direction, the control valve 175 moves to shut off the center bypass pipeline 40, causing the control pressure detected by the control pressure sensor 19 to decrease. Therefore, the required flow rate Q calculated based on the control pressure decreases. * This increases in response to a decrease in control pressure. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 is equal to the required flow rate Q. * It increases in accordance with the increase in the actual discharge volume due to the increase in Q. Therefore, the required flow rate Q * The required torque T is calculated based on the discharge pressure P. * The demand for torque T has increased sharply. * The allowable torque T calculated based on limit However, as shown by the dashed line in Figure 4(A), it increases sharply.

[0063] Furthermore, if the fluctuation suppression unit E3 is not present, that is, the torque limit value T" limit Instead of allowable torque T limitWhen this is input to the flow rate command calculation unit E4, the engine speed decreases as shown by the dashed line in Figure 4(B). This is because the absorption torque of the main pump 14 temporarily exceeds the actual torque of the engine 11. This is compared to when the fluctuation suppression unit E3 is present, i.e., when the torque limit value T" limit This is because, compared to when the flow rate command value Q is input to the flow rate command calculation unit E4, the flow rate command value Q, i.e., the actual discharge volume of the main pump 14, becomes larger. Such a sudden increase in the actual discharge volume of the main pump 14 is due to the required flow rate Q * This can also occur if the value is used directly as the flow rate command value Q.

[0064] Therefore, in the example shown in Figure 4, the controller 30 (flow rate command calculation unit E4) calculates the torque limit value T" calculated by the fluctuation suppression unit E3. limit By determining the flow rate command value Q based on this, a sudden increase in the actual discharge volume of the main pump 14 is suppressed. As a result, the controller 30 can maintain the engine speed as shown by the solid line in Figure 4(B) and prevent a significant drop in engine speed as shown by the dashed line in Figure 4(B). This is because the controller 30 can prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11.

[0065] Next, referring to Figure 5, the effect of the fluctuation suppression process using the controller 30, which includes another fluctuation suppression unit E3, will be explained. Figure 5, like Figure 4, shows the temporal changes in values ​​related to the fluctuation suppression process when a boom raising operation is performed. Specifically, Figure 5 includes Figures 5(A) and 5(B). Figure 5(A) shows the temporal changes in values ​​related to torque. The values ​​related to torque are the allowable torque T limit and torque limit value T" limit This includes [the following]. Figure 5(B) shows the change in engine speed over time.

[0066] In the example shown in Figure 5, the fluctuation suppression unit E3 controls the target rotational speed ω of the engine 11. * The torque limit value T" is determined based on the difference Δω between the actual rotational speed ω and the actual rotational speed ω. limit It is configured to determine this.

[0067] Target rotational speed ω of engine 11 * For example, in order to apply an additional load to the engine 11 without overloading it, the engine speed is higher than the current engine speed by the amount of rotational speed difference corresponding to that additional load.

[0068] Specifically, the fluctuation suppression unit E3 controls the allowable torque T calculated by the torque limiting unit E2. limit And, target rotation speed ω * The system receives the actual rotational speed ω detected by the engine speed sensor (not shown) as input, and uses equation (4) to calculate the torque limit value T" limit Calculate the coefficient K. P The constant of proportionality is the coefficient K. I is the integration constant.

[0069]

number

[0070] At time t1, when the right operating lever 26R is operated in the boom-raising direction, the control valve 175 moves to shut off the center bypass pipeline 40, causing the control pressure detected by the control pressure sensor 19 to decrease. Therefore, the required flow rate Q calculated based on the control pressure decreases. * This increases in response to a decrease in control pressure. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 is equal to the required flow rate Q. *It increases in accordance with the increase in the actual discharge volume due to the increase in Q. Therefore, the required flow rate Q * The required torque T is calculated based on the discharge pressure P. * The demand for torque T has increased sharply. * The allowable torque T calculated based on limit However, as shown by the dashed line in Figure 5(A), it increases sharply.

[0071] Furthermore, if the fluctuation suppression unit E3 is not present, that is, the torque limit value T" limit Instead of allowable torque T limit When this is input to the flow rate command calculation unit E4, the engine speed decreases as shown by the dashed line in Figure 5(B). This is because the absorption torque of the main pump 14 temporarily exceeds the actual torque of the engine 11. This is because, compared to when the fluctuation suppression unit E3 is present, the torque limit value T" calculated using equation (4) is lower. limit This is because, compared to when the flow rate command value Q is input to the flow rate command calculation unit E4, the flow rate command value Q, i.e., the actual discharge volume of the main pump 14, becomes larger. Such a sudden increase in the actual discharge volume of the main pump 14 is due to the required flow rate Q * This can also occur if the value is used directly as the flow rate command value Q.

[0072] Therefore, in the example in Figure 5, similar to the example in Figure 4, the controller 30 calculates the torque limit value T" using equation (4). limit By determining the flow rate command value Q based on this, the rapid increase in the actual discharge volume of the main pump 14 is suppressed. As a result, the controller 30 can maintain the engine speed as shown by the solid line in Figure 5(B) and prevent the engine speed from dropping sharply as shown by the dashed line in Figure 5(B). This is because the controller 30 can prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11. Specifically, the controller 30 sets the target engine speed ω to a value higher than the current engine speed by the amount of rotational speed difference corresponding to an additional load that does not overload the engine 11. * This approach allows the absorption torque of the main pump 14 to increase gradually without abruptly.

[0073] As described above, the excavator 100 comprises a lower traveling body 1, an upper rotating body 3 rotatably mounted on the lower traveling body 1, an engine 11 mounted on the upper rotating body 3, a main pump 14 as a hydraulic pump driven by the engine 11, and a controller 30 as a control device that controls the flow rate of the hydraulic fluid discharged by the main pump 14. The controller 30 is configured to delay (reduce) the responsiveness of the main pump 14 when the load on the engine 11 increases, until the actual torque of the engine 11 rises to a level corresponding to the load.

[0074] This configuration allows the shovel 100 to more reliably prevent the absorption torque of the main pump 14 from exceeding the actual torque of the engine 11. In other words, the shovel 100 can efficiently increase the absorption torque of the main pump 14, i.e., the actual torque of the engine 11. This is because the shovel 100 can pre-limit the discharge amount of the main pump 14 in anticipation of the delay in the rise of engine output. That is, the shovel 100 can respond to the dynamic changes in the actual torque of the engine 11. Therefore, the shovel 100 can suppress the decrease in engine speed. As a result, the shovel 100 can improve fuel efficiency. In addition, the shovel 100 can reduce the discomfort experienced by the operator regarding fluctuations in engine speed during operation.

[0075] Furthermore, by providing the fluctuation suppression unit E3, the Shovel 100 can prevent a sudden increase in the absorption torque of the main pump 14, i.e., the engine load, and prevent the engine speed from becoming unstable, not only when the boost pressure is relatively low, but also when the boost pressure is relatively high.

[0076] The controller 30 may be configured in a manner other than that described in the above-described embodiment to increase the flow rate of the hydraulic fluid discharged by the main pump 14 in accordance with the rise in the actual torque of the engine 11. For example, the controller 30 may be configured to increase the flow rate of the hydraulic fluid discharged by the main pump 14 at an increase rate corresponding to the increase in the actual torque of the engine 11. In this case, the increase rate of the flow rate of the hydraulic fluid discharged by the main pump 14 may be preset based on at least one of past data and simulation results.

[0077] The controller 30 controls the required flow rate Q, which is the flow rate of the hydraulic fluid that the main pump 14 should discharge, in a manner other than that described in the above-described embodiment. * The system may be configured to suppress the increase in the flow rate command value Q, which corresponds to the flow rate of the hydraulic fluid actually discharged by the main pump 14, in response to the increase in the main pump 14.

[0078] The controller 30, in a manner other than that described in the above-described embodiment, controls the requested flow rate Q * The required torque T needed to achieve this * Torque limit value T" based on limit Calculate the torque limit value T" limit The system may be configured to calculate the flow rate command value Q based on this.

[0079] Preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the embodiments described above. Various modifications or substitutions can be applied to the embodiments described above without departing from the scope of the present invention. Furthermore, features described separately can be combined as long as no technical inconsistencies arise.

[0080] For example, in the above-described embodiment, the hydraulic system mounted on the shovel 100 is configured to perform negative control as an energy-saving control, but it may also be configured to perform positive control or load sensing control, etc. When positive control is employed, the controller 30, for example, determines the required flow rate Q based on the operating pressure detected by the operating pressure sensor 29. * It may also be configured to calculate the required flow rate Q. Furthermore, if load sensing control is employed, the controller 30 may, for example, calculate the required flow rate Q based on the output of a load pressure sensor that detects the pressure of the hydraulic fluid in the actuator and the discharge pressure detected by the discharge pressure sensor 28. * It may be configured to calculate the following.

[0081] Furthermore, in the above-described embodiment, the controller 30 performs fluctuation suppression processing when a boom raising operation is performed, but the fluctuation suppression processing may also be performed when at least one of the following operations is performed: boom lowering operation, arm closing operation, arm opening operation, bucket closing operation, bucket opening operation, slewing operation, and travel operation.

[0082] Furthermore, in the above-described embodiment, a hydraulic operating lever equipped with a hydraulic pilot circuit is disclosed. For example, in the hydraulic pilot circuit for the left operating lever 26L, the hydraulic fluid supplied from the pilot pump 15 to the left operating lever 26L is transmitted to the pilot port of the control valve 176 at a flow rate corresponding to the opening degree of the remote control valve, which is opened and closed by the tilting of the left operating lever 26L in the arm-opening direction. Alternatively, in the hydraulic pilot circuit for the right operating lever 26R, the hydraulic fluid supplied from the pilot pump 15 to the right operating lever 26R is transmitted to the pilot port of the control valve 175 at a flow rate corresponding to the opening degree of the remote control valve, which is opened and closed by the tilting of the right operating lever 26R in the boom-raising direction.

[0083] However, instead of a hydraulic operating lever equipped with such a hydraulic pilot circuit, an electric operating lever equipped with an electric pilot circuit may be used. In this case, the amount of lever operation of the electric operating lever is input to the controller 30 as an electrical signal, for example. A solenoid valve is also placed between the pilot pump 15 and the pilot port of each control valve. The solenoid valve is configured to operate in response to an electrical signal from the controller 30. With this configuration, when manual operation is performed using the electric operating lever, the controller 30 can move each control valve by controlling the solenoid valve in accordance with the electrical signal corresponding to the amount of lever operation, thereby increasing or decreasing the pilot pressure.

[0084] This application claims priority based on Japanese Patent Application No. 2019-068992, filed on 29 March 2019, and the entire contents of that Japanese Patent Application are incorporated herein by reference. [Explanation of symbols]

[0085] 1. Lower travel body 2. Swivel mechanism 2A. Swivel hydraulic motor 2M. Travel hydraulic motor 2ML. Left travel hydraulic motor 2MR. Right travel hydraulic motor 3. Upper slewing body 4. Boom 5. Arm 6. Bucket 7. Boom cylinder 8. Arm cylinder 9. Bucket cylinder 10. Cabin 11. Engine 13. Regulator 14. Main pump 15. Pilot pump 17. Control valve 18. Throttle 19. Control pressure sensor 26. Operating device 28. Discharge pressure sensor 29. Operating pressure sensor 30. Controller 40. Center bypass pipeline 42. Parallel pipeline 75. Engine speed adjustment dial 100. Excavator 171-176... Control valve E1... Required torque calculation unit E2... Torque limiting unit E3... Fluctuation suppression unit E4... Flow rate command calculation unit

Claims

1. Lower running body and An upper slewing body is mounted on the lower traveling body so as to be rotatable, The engine mounted on the upper rotating body, A boost pressure sensor for detecting the boost pressure of a supercharger provided in the engine, A hydraulic pump driven by the aforementioned engine, The system includes a control device that controls the flow rate of the hydraulic fluid discharged by the hydraulic pump, The control device calculates the required flow rate of the hydraulic pump based on at least one of the control pressure detected by a control pressure sensor functioning as a negative control pressure sensor, the discharge pressure of the hydraulic pump detected by a discharge pressure sensor, and the operating pressure detected by an operating pressure sensor. It also calculates the required torque necessary to achieve the required flow rate, and even before the engine load increases, it calculates a torque limit value that limits the required torque according to the boost pressure detected by the boost pressure sensor. Based on the torque limit value, it controls the hydraulic pump to delay the responsiveness of the hydraulic pump until the actual torque of the engine rises to a level corresponding to the engine load when the engine load increases. Shovel.

2. Lower traveling body and An upper slewing body is mounted on the lower traveling body so as to be rotatable, The engine mounted on the upper rotating body, A boost pressure sensor for detecting the boost pressure of a supercharger provided in the engine, A hydraulic pump driven by the aforementioned engine, The system includes a control device that controls the flow rate of the hydraulic fluid discharged by the hydraulic pump, The control device calculates the required torque necessary to achieve the required flow rate of the hydraulic pump, and even before the engine load increases, it calculates a torque limit value that limits the required torque according to the boost pressure detected by the boost pressure sensor, calculates a value obtained by suppressing fluctuations from the torque limit value through a delay filter, and controls the hydraulic pump based on the value suppressed by fluctuations, thereby delaying the responsiveness of the hydraulic pump when the engine load increases until the actual torque of the engine rises to a level corresponding to the engine load. Shovel.

3. Lower traveling body and An upper slewing body is mounted on the lower traveling body so as to be rotatable, The engine mounted on the upper rotating body, A boost pressure sensor for detecting the boost pressure of a supercharger provided in the engine, A hydraulic pump driven by the aforementioned engine, A control device for controlling the flow rate of the hydraulic fluid discharged by the hydraulic pump, The system includes an engine speed sensor for detecting the actual rotational speed of the engine, The control device calculates the required torque necessary to achieve the required flow rate of the hydraulic pump, and even before the engine load increases, it calculates a torque limit value that limits the required torque according to the boost pressure detected by the boost pressure sensor, calculates a value with suppressed fluctuations from the torque limit value based on the difference between the actual rotational speed detected by the engine speed sensor and the target rotational speed of the engine, and controls the hydraulic pump based on the value with suppressed fluctuations to delay the responsiveness of the hydraulic pump until the actual torque of the engine rises to a level corresponding to the engine load when the engine load increases. Shovel.

4. The control device calculates the flow rate command value of the hydraulic pump based on the torque limit value. The shovel according to claim 1.

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