阅读说明：本技术 挖土机 (Excavator ) 是由 佐野公则 白谷龙二 于 2020-03-27 设计创作，主要内容包括：本发明提供一种挖土机。挖土机(100)具备下部行走体(1)、回转自如地搭载于下部行走体(1)的上部回转体(3)、搭载于上部回转体(3)的引擎(11)、由引擎(11)驱动的主泵(14)及控制主泵(14)吐出的工作油的流量的控制器(30)。控制器(30)在引擎(11)的负载增大时使主泵(14)的响应性延迟,直至引擎(11)的实际转矩上升至与负载相对应的水平。(The invention provides an excavator. A shovel (100) is provided with a lower traveling body (1), an upper revolving body (3) rotatably mounted on the lower traveling body (1), an engine (11) mounted on the upper revolving body (3), a main pump (14) driven by the engine (11), and a controller (30) for controlling the flow rate of hydraulic oil discharged from the main pump (14). The controller (30) delays the responsiveness of the main pump (14) when the load of the engine (11) increases until the actual torque of the engine (11) rises to a level corresponding to the load.)

1. A shovel is provided with:

a lower traveling body;

an upper revolving structure rotatably mounted on the lower traveling structure;

an engine mounted on the upper slewing body;

a hydraulic pump driven by the engine; and

a control device for controlling the flow rate of the hydraulic oil discharged from the hydraulic pump,

the control device delays responsiveness of the hydraulic pump when a load of the engine increases until an actual torque of the engine rises to a level corresponding to the load of the engine.

2. The shovel of claim 1,

the control device increases the flow rate of the hydraulic oil discharged from the hydraulic pump in accordance with an increase in the actual torque of the engine.

3. The shovel of claim 1,

the control device suppresses an increase in the flow rate of the hydraulic oil actually discharged by the hydraulic pump with respect to an increase in a required flow rate, which is the flow rate of the hydraulic oil to be discharged by the hydraulic pump.

4. The shovel of claim 1,

the control device calculates a torque limit value from a required torque required to achieve a required flow rate, and calculates a flow rate command value from the torque limit value.

5. The shovel of claim 1,

the control device also calculates a flow rate command value that delays responsiveness of the hydraulic pump before a load of the engine increases.

6. The shovel of claim 1,

the control device also calculates a torque limit value that delays responsiveness of the hydraulic pump before a load of the engine increases.

7. The shovel of claim 1,

the control device estimates an output state of the engine based on a required flow rate that is a flow rate of the hydraulic oil to be discharged by the hydraulic pump.

8. The shovel of claim 7,

the control device suppresses an increase in the flow rate of the hydraulic pump according to the inferred output state of the engine.

Technical Field

The present invention relates to an excavator as an excavator.

Background

Conventionally, a shovel is known which controls a discharge amount of a hydraulic pump so that an absorption torque of the hydraulic pump does not exceed a rated torque of an engine even if a discharge pressure of the hydraulic pump changes (see patent document 1).

When the engine load is small, the actual torque of the engine rotating at a prescribed rotation speed changes at a level smaller than the rated torque. Then, when the engine load increases, the actual torque increases by the increase in the fuel injection amount, and reaches the rated torque. In this way, the actual torque dynamically changes, and increases with a certain delay when the engine load increases.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-2318

Disclosure of Invention

Technical problem to be solved by the invention

However, the control in the above-described excavator does not take into account the delay associated with the rise of the actual torque of the engine. Therefore, in the control of the excavator, the absorption torque of the hydraulic pump temporarily exceeds the actual torque of the engine, and the engine rotation speed may be reduced.

Therefore, it is desirable to more reliably prevent the absorption torque of the hydraulic pump from exceeding the actual torque of the engine.

Means for solving the technical problem

An excavator according to an embodiment of the present invention includes: a lower traveling body; an upper revolving structure rotatably mounted on the lower traveling structure; an engine mounted on the upper slewing body; a hydraulic pump driven by the engine; and a control device that controls a flow rate of the hydraulic oil discharged by the hydraulic pump, wherein the control device delays responsiveness of the hydraulic pump until an actual torque of the engine increases to a level corresponding to the load when the load of the engine increases.

ADVANTAGEOUS EFFECTS OF INVENTION

With the above arrangement, it is possible to provide a shovel capable of more reliably preventing the absorption torque of the hydraulic pump from exceeding the actual torque of the engine.

Drawings

Fig. 1 is a side view of a shovel according to an embodiment of the present invention.

Fig. 2 is a diagram showing a configuration example of a hydraulic system mounted on a shovel.

Fig. 3 is a diagram showing a configuration example of the controller.

Fig. 4 shows an example of a temporal change in a value related to the fluctuation suppression processing when the boom raising operation is performed.

Fig. 5 shows another example of temporal changes in values related to the fluctuation suppression processing when the boom raising operation is performed.

Detailed Description

First, a shovel 100 as an excavator according to an embodiment of the present invention will be described with reference to fig. 1. Fig. 1 is a side view of an excavator 100. In the present embodiment, an upper turning body 3 is rotatably mounted on the lower traveling body 1 via a turning 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 belt and a right traveling hydraulic motor 2MR (not visible in fig. 1) that drives the right crawler belt. The turning mechanism 2 is driven by a turning hydraulic motor 2A mounted on the upper turning body 3. However, the turning hydraulic motor 2A may be a turning motor generator as an electric actuator.

A boom 4 is attached to the upper slewing body 3. An arm 5 is attached to a tip end of the boom 4, and a bucket 6 as a terminal attachment is attached to a tip end of the arm 5. The boom 4, the arm 5, and the bucket 6 constitute an excavation attachment as an example of an attachment. Boom 4 is driven by boom cylinder 7, arm 5 is driven by arm cylinder 8, and bucket 6 is driven by bucket cylinder 9.

A cabin 10 as a cab is provided in the upper slewing body 3, and a power source such as an engine 11 is mounted thereon. Further, a controller 30 is attached to the upper slewing body 3. In the present specification, for convenience, the side of the upper slewing body 3 to which the boom 4 is attached is referred to as the front side, and the side to which the counterweight (counter weight) is attached is referred to as the rear side.

The controller 30 is a control device for controlling the shovel 100. In the present embodiment, the controller 30 is configured by a computer including a CPU, a volatile memory device, a nonvolatile memory device, and the like. The controller 30 is configured to read out programs corresponding to various functional elements from the nonvolatile storage device, load the programs into a volatile storage device such as a RAM, and execute corresponding processing by the CPU, thereby realizing various functions.

Next, a configuration example of a hydraulic system mounted on the shovel 100 will be described with reference to fig. 2. Fig. 2 shows a configuration example of a hydraulic system mounted on the shovel 100. In fig. 2, a mechanical power transmission system, a hydraulic oil line, a pilot line, and an electric control system are shown by a double line, a solid line, a broken line, and a dotted line, 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 17, an operation device 26, a discharge pressure sensor 28, an operation pressure sensor 29, a controller 30, an engine speed adjustment dial 75, and the like.

In fig. 2, the hydraulic system circulates hydraulic oil from the main pump 14 driven by the engine 11 to a hydraulic oil tank through at least one of an intermediate bypass line 40 and a parallel line 42.

The engine 11 is a drive source of the shovel 100. In the present embodiment, the engine 11 is, for example, a diesel engine that operates to maintain a predetermined number of revolutions. The output shaft of the engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15, respectively. The engine 11 is provided with a supercharger. In the present embodiment, the supercharger is a turbocharger. The engine 11 is controlled by an engine control unit. The engine control unit is configured to adjust the fuel injection amount in accordance with, for example, boost pressure (boost pressure). The boost pressure is detected by, for example, a boost pressure sensor.

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

Regulator 13 controls the discharge rate of main pump 14. In the present 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 accordance with a control command from the controller 30 to control the displacement of the main pump 14 per rotation.

The pilot pump 15 is configured to supply hydraulic oil to a hydraulic control apparatus including an operation device 26 via a pilot line. In the present embodiment, the pilot pump 15 is a fixed displacement hydraulic pump. The pilot pump 15 may be omitted. In this case, the function of the pilot pump 15 can be performed by the main pump 14. That is, the main pump 14 may have a function of supplying the hydraulic oil to the operation device 26 and the like after reducing the pressure of the hydraulic oil by an orifice and the like in addition to the function of supplying the hydraulic oil to the control valve 17.

The control valve 17 is a hydraulic control device that controls a hydraulic system in the shovel 100. In the present embodiment, the control valve 17 includes control valves 171 to 176 as shown by the one-dot chain line. 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 17 can selectively supply the hydraulic oil discharged from the main pump 14 to one or more hydraulic actuators via the control valves 171 to 176. The control valves 171 to 176 control the flow rate of the hydraulic oil flowing from the main pump 14 to the hydraulic actuators and the flow rate of the 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 turning hydraulic motor 2A.

The operating device 26 is a device for an operator to operate the actuator. The actuator includes at least one of a hydraulic actuator and an electric actuator. In the present embodiment, the operation device 26 supplies the hydraulic oil discharged from the pilot pump 15 to the pilot port of the corresponding control valve in the control valve 17 via the pilot line. The pilot pressure, which is the pressure of the hydraulic oil supplied to each pilot port, is a pressure corresponding to the operation direction and the operation amount of a lever or a pedal (not shown) of the operation device 26, and the lever or the pedal of the operation device 26 corresponds to each hydraulic actuator.

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

The operation pressure sensor 29 is configured to detect the content of an operation via the operation device 26. In the present embodiment, the operation pressure sensor 29 detects the operation direction and the operation amount of a lever or a pedal as the operation device 26 corresponding to each actuator as pressure (operation pressure), and outputs the detected values to the controller 30. The operation content of the operation device 26 may be detected by a sensor other than the operation pressure sensor.

Main pump 14 includes a left main pump 14L and a right main pump 14R. The left main pump 14L circulates the hydraulic oil to the hydraulic oil tank through the left intermediate bypass line 40L or the left parallel line 42L, and the right main pump 14R circulates the hydraulic oil to the hydraulic oil tank through the right intermediate bypass line 40R or the right parallel line 42R.

The left intermediate bypass line 40L is a hydraulic oil line passing through the control valves 171, 173, 175L, and 176L disposed in the control valve 17. The right middle bypass line 40R is a hydraulic oil line passing through the control valves 172, 174, 175R, and 176R disposed in the control valve 17.

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

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

The control valve 173 is a spool valve that switches the flow of the hydraulic oil in order to supply the hydraulic oil discharged from the left main pump 14L to the hydraulic motor 2A for turning and discharge the hydraulic oil discharged from the hydraulic motor 2A for turning to a hydraulic oil tank.

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

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

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

The left parallel line 42L is a working oil line in parallel with the left intermediate bypass line 40L. When the flow of the working oil through the left intermediate bypass line 40L is restricted or shut off by any one of the control valves 171, 173, and 175L, the left parallel line 42L can supply the working oil to the control valves further downstream. The right parallel line 42R is a working oil line in parallel with the right intermediate bypass line 40R. When the flow of the working oil through the right intermediate bypass line 40R is restricted or shut off by any one of the control valves 172, 174, and 175R, the right parallel line 42R can supply the working oil to the control valves further downstream.

The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L is configured to control the discharge rate 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 adjusting the swash plate tilting angle of the left main pump 14L in accordance with, for example, an increase in the discharge pressure of the left main pump 14L to reduce the displacement per rotation. The same applies to the right regulator 13R. This is to avoid the absorbed power (e.g., absorption horsepower) of the main pump 14, which is expressed by the product of the discharge pressure and the discharge amount, from exceeding the output power (e.g., output horsepower) of the engine 11.

Operation device 26 includes a left operation lever 26L, a right operation lever 26R, and a travel lever 26D. The travel bar 26D includes a left travel bar 26DL and a right travel bar 26 DR.

The left operation lever 26L is used for the swing operation and the operation of the arm 5. When the control is performed in the forward/backward direction, the left control lever 26L introduces a pilot pressure corresponding to the lever operation amount to the pilot port of the control valve 176 by the hydraulic oil discharged from the pilot pump 15. When the control valve is operated in the left-right direction, the pilot pressure corresponding to the lever operation amount is introduced into the pilot port of the control valve 173 by the hydraulic oil discharged from the pilot pump 15.

Specifically, when operated in the arm closing direction, the left control lever 26L introduces hydraulic oil to the right pilot port of the control valve 176L and introduces hydraulic oil to the left pilot port of the control valve 176R. When the arm opening direction is operated, the left control lever 26L introduces hydraulic oil to the left pilot port of the control valve 176L and introduces hydraulic oil to the right pilot port of the control valve 176R. When the left swing direction is operated, the left operation lever 26L introduces hydraulic oil to the left pilot port of the control valve 173, and when the right swing direction is operated, the hydraulic oil is introduced to the right pilot port of the control valve 173.

The right operation lever 26R is used for the operation of the boom 4 and the operation of the bucket 6. When the control is performed in the forward/backward direction, the right control lever 26R introduces a pilot pressure corresponding to the lever operation amount to the pilot port of the control valve 175 by the hydraulic oil discharged from the pilot pump 15. When the control valve is operated in the left-right direction, the pilot pressure corresponding to the lever operation amount is introduced into the pilot port of the control valve 174 by the hydraulic oil discharged from the pilot pump 15.

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

The travel bar 26D is used for the operation of the crawler. Specifically, the left travel bar 26DL is used for operation of the left track. The left travel lever 26DL may be configured to be linked with a left travel pedal. When the left travel lever 26DL is operated in the forward/rearward direction, pilot pressure corresponding to the lever operation amount is introduced into the pilot port of the control valve 171 by the hydraulic oil discharged from the pilot pump 15. Right travel bar 26DR is used for operation of the right side track. The right travel lever 26DR is configured to be linked with a right travel pedal. When the right travel lever 26DR is operated in the forward/rearward direction, the pilot pressure corresponding to the lever operation amount is introduced into the pilot port of the control valve 172 by the hydraulic oil discharged from the pilot pump 15.

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.

The operation pressure sensors 29 include operation pressure sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29 DR. The operation pressure sensor 29LA detects the operation content in the front-rear direction with respect to the left operation lever 26L as pressure, and outputs the detected value to the controller 30. The operation contents include, for example, a lever operation direction and a lever operation amount (lever operation angle).

Similarly, the operation pressure sensor 29LB detects the operation content in the left-right direction with respect to the left operation lever 26L as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29RA detects the operation content in the front-rear direction with respect to the right operation lever 26R as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29RB detects the operation content in the left-right direction with respect to the right operation lever 26R as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29DL detects the operation content in the front-rear direction with respect to the left travel lever 26DL as pressure, and outputs the detected value to the controller 30. The operation pressure sensor 29DR detects the operation content in the front-rear direction with respect to the right travel lever 26DR as pressure, and outputs the detected value to the controller 30.

Controller 30 may receive the output of operating pressure sensor 29 and output control commands to regulator 13 to vary the discharge rate of primary pump 14 as desired.

The controller 30 is configured to execute negative control as energy saving control using the throttle 18 and the control pressure sensor 19. The throttle 18 includes a left throttle 18L and a right throttle 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R. In the present embodiment, the control pressure sensor 19 functions as a negative control pressure sensor. The energy saving control is control for reducing the discharge rate of the main pump 14 in order to suppress wasteful energy consumption by the main pump 14.

A left choke 18L is disposed between the control valve 176L located at the most downstream position and the hydraulic oil tank in the left intermediate bypass line 40L. Therefore, the flow of the hydraulic oil discharged from the left main pump 14L is restricted by the left throttle 18L. Also, the left orifice 18L generates a control pressure (negative control pressure) for controlling the left regulator 13L. The left control pressure sensor 19L is a sensor for detecting the 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 negative control by adjusting the swash plate tilt angle of the left main pump 14L in accordance with the control pressure. The controller 30 decreases the discharge rate of the left main pump 14L as the control pressure increases, and the controller 30 increases the discharge rate of the left main pump 14L as the control pressure decreases. The discharge rate of the right main pump 14R is also controlled in the same manner.

Specifically, as shown in fig. 2, when none of the hydraulic actuators in the shovel 100 is operated, that is, when the shovel 100 is in a standby state, the hydraulic oil discharged from the left main pump 14L reaches the left throttle 18L through the left intermediate bypass line 40L. Then, the flow of the 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 standby flow rate, and suppresses the pressure loss (pump loss) when the discharged hydraulic oil passes through the left intermediate bypass line 40L. The standby flow rate is a predetermined flow rate used in the standby state, and is, for example, an allowable minimum discharge rate. On the other hand, when any of the hydraulic actuators is operated, the hydraulic oil discharged from the left main pump 14L flows into the hydraulic actuator to be operated via the control valve corresponding to the hydraulic actuator to be operated. Then, the control valve corresponding to the hydraulic actuator to be operated reduces or eliminates the flow rate of the hydraulic oil reaching the left orifice 18L, thereby reducing the control pressure generated upstream of the left orifice 18L. As a result, the controller 30 increases the discharge rate of the left main pump 14L, and circulates sufficient hydraulic oil to the hydraulic actuator to be operated so that the hydraulic actuator to be operated can be reliably driven. The controller 30 also controls the discharge rate of the right main pump 14R in the same manner.

By the negative control as described above, the hydraulic system of fig. 2 can suppress wasteful energy consumption in the main pump 14 in the standby state. The wasted energy consumption includes pump loss in the intermediate bypass line 40 caused by the working oil discharged from the main pump 14. When the hydraulic actuator is operated, the hydraulic system of fig. 2 can reliably supply a sufficient amount of hydraulic oil from the main pump 14 to the hydraulic actuator to be operated.

The engine speed adjustment dial 75 is a dial for adjusting the speed of the engine 11. The engine speed adjustment dial 75 transmits data indicating the setting state of the engine speed to the controller 30. In the present embodiment, the engine speed adjustment dial 75 is configured to be able to switch the engine speed in 4 stages of the SP mode, the H mode, the a mode, and the IDLE mode. The SP mode is a rotational speed mode selected when the workload is to be prioritized, and uses the highest engine rotational speed. The H-mode is a speed mode selected when both workload and fuel consumption are to be considered, utilizing the second highest engine speed. The a mode is a rotational speed mode selected when the shovel 100 is to be operated with low noise while giving priority to fuel efficiency, and the third highest engine rotational speed is used. The IDLE mode is a rotation speed mode selected when the engine 11 is to be set to an IDLE operation state, and the lowest engine rotation speed is used. The engine 11 is constantly rotation-controlled at the engine rotation speed in the rotation speed mode set by the engine rotation speed adjustment dial 75.

Next, a process of suppressing the fluctuation of the flow rate command value Q output from the regulator 13 by the controller 30 (hereinafter referred to as "fluctuation suppression process") will be described with reference to fig. 3. Fig. 3 is a diagram showing a configuration example of the controller 30.

In the present embodiment, the controller 30 includes a requested torque calculation unit E1, a torque limitation unit E2, and a fluctuation suppression unitA controller E3 and a flow rate command calculator E4. The controller 30 is configured to receive the requested flow rate Q at every predetermined control cycle^*Discharge pressure P and boost pressure P_BEtc. as inputs and outputs a torque limit value T "_limitAnd a flow rate command value Q.

Required flow rate Q^*Is a value calculated as the flow rate of the hydraulic oil to be discharged from the main pump 14. The controller 30 calculates 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, the operation pressure detected by the operation pressure sensor 29, and the like^*. Required flow rate Q^*Or may be calculated by the control pressure sensor 19. At this time, the pressure sensor 19 is controlled to output the required flow rate Q to the controller 30^*. In the present embodiment, the controller 30 calculates the required flow rate Q from the control pressure detected by the control pressure sensor 19^*。

The required torque calculation unit E1 is configured to calculate the required torque T^*. Required torque T^*As to achieve the required flow rate Q^*The required torque. In the present embodiment, the required torque calculation unit E1 receives the required flow rate Q^*And the discharge pressure P as input, and calculating the required torque T using the equation (1)^*。

[ numerical formula 1]

The torque limiter E2 is configured to limit the required torque T^*. In the present embodiment, the torque limiter E2 limits the required torque T^*So that the required torque T^*The rated torque of the engine 11 is not exceeded. Specifically, the torque limiter unit E2 receives the required torque T calculated by the required torque calculator unit E1^*And boost pressure P detected by the boost pressure sensor_BAs an input, the allowable torque T is output to the fluctuation suppression unit E3_limit. More specifically, the torque limiter portion E2 responds to the boost pressure P_BCalculating the permissible torque T according to the uniquely determined load factor L_limit. The load factor L (%) is, for example, the allowable torque T of the engine 11_limitRatio with respect to the engine rated torque. Equation (2) represents the allowable torque T_limitRequested torque T^*And the load factor L (%).

[ numerical formula 2]

T_limit＝T^*×L ……(2)

The fluctuation suppression unit E3 is configured to suppress the allowable torque T_limitA variation of (c). In the present embodiment, the fluctuation suppression unit E3 has a time constant T_SThe first order delay filter of (1) functions to limit the allowable torque T per predetermined control period_limitThe amplitude of variation of (d). Specifically, fluctuation suppression unit E3 receives allowable torque T calculated by torque limitation unit E2_1imitAs an input, the torque limit value T is output to the flow rate command calculation unit E4 "_limit。

The flow rate command calculation unit E4 is configured to calculate a flow rate command value Q to be output to the regulator 13. In the present embodiment, the flow rate command calculation unit E4 receives the discharge pressure P detected by the discharge pressure sensor 28 and the torque limit value T calculated by the fluctuation suppression unit E3 "_limitAs an input, the flow rate command value Q is calculated using equation (3).

[ numerical formula 3]

In this manner, the controller 30 obtains the demanded flow rate Q by the torque limiter unit E2 and the fluctuation suppressor unit E3^*And the output state of the engine 11 (torque limit value T) of the discharge pressure P "_1imit) Then, the flow rate command calculation unit E4 calculates a flow rate command value Q corresponding to the output state of the engine 11. With the above configuration, the controller 30 can be prevented from being at the boost pressure P_BThe flow rate command value Q increases excessively before sufficiently rising. Therefore, the controller 30 can prevent the absorption torque of the main pump 14 from excessively increasing in a state where the actual torque of the engine 11 is low. That is, the controller 30 canIt is possible to prevent the absorption torque of the main pump 14 from sharply increasing to cause a sharp decrease in the engine speed in a state where the actual torque of the engine 11 is low. This is because, even when the absorption torque of the main pump 14 is lower than the rated torque of the engine 11, if the absorption torque of the main pump 14 exceeds the actual torque of the engine 11, the engine speed decreases. In addition, the absorption torque of the main pump 14 is typically expressed by the product of the discharge pressure and the discharge amount. In this manner, controller 30 can more reliably prevent the engine 11 from being operated at supercharging pressure P by preventing the absorption torque of main pump 14 from exceeding the actual torque of engine 11_BThe engine speed drops before rising sufficiently.

Next, the effect of the fluctuation suppression processing will be described with reference to fig. 4. Fig. 4 shows a time-dependent change in the value related to the fluctuation suppression processing when the boom raising operation is performed. Specifically, fig. 4 includes fig. 4 (a) and fig. 4 (B). Fig. 4 (a) shows a change in the value related to the torque with time. The torque-related value includes an allowable torque T_limitAnd torque limit value T'_limit. Fig. 4 (B) shows the change in the engine speed with time.

More specifically, the broken line in fig. 4 (a) indicates the allowable torque T derived by the torque limiter E2 for each predetermined control cycle_limitChange over time. The solid line in fig. 4 (a) represents the torque limit value T derived by the fluctuation suppression unit E3 for each predetermined control cycle "_limitChange over time. The broken line in fig. 4 (B) indicates that the fluctuation suppression unit E3 is not present, that is, the torque limit value T is replaced "_limitWhile allowing the torque T_limitThe change over time in the engine speed when input to the flow rate command calculation unit E4. The solid line in fig. 4 (B) indicates the presence of the fluctuation suppression unit E3, that is, the torque limit value T "_limitThe change over time in the engine speed when input to the flow rate command calculation unit E4.

From time t0 to time t1, the hydraulic load due to the operation is not applied to the engine 11. During this period, the controller 30 estimates the demanded flow rate Q by the torque limiter unit E2 and the fluctuation suppression unit E3^*And the output state of the engine 11 (torque limit value T) of the discharge pressure P "_limit) And the flow rate command calculation unit E4 calculates and controls the engine 11, and a flow rate command value Q corresponding to the output state. Therefore, the controller 30 also calculates the torque limit value T that delays the responsiveness of the main pump 14 before the load of the engine 11 increases "_limit. Therefore, controller 30 calculates a flow rate command value Q that delays the responsiveness of main pump 14.

Therefore, the controller 30 can reduce the engine output by calculating a smaller flow rate command value Q in a state where a large load is not applied.

At time t1, when the right control lever 26R is operated in the boom raising direction, the control valve 175 moves to block the intermediate bypass line 40, and thus the control pressure detected by the control pressure sensor 19 decreases. Therefore, the required flow rate Q calculated from the control pressure^*Increasing as the control pressure decreases. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 follows the required flow rate Q^*The actual discharge amount increases due to the increase in the amount of the ink. Therefore, according to the required flow rate Q^*And the required torque T calculated from the discharge pressure P^*Sharply increased according to the required torque T^*Calculated allowable torque T_limitAnd also sharply increases as shown by the broken line in fig. 4 (a).

Also, when there is no fluctuation suppression portion E3, that is, when replacing the torque limit value T "_limitWhile allowing the torque T_limitWhen the engine speed is input to the flow rate command calculation unit E4, the engine speed decreases as indicated by the broken line in fig. 4 (B). This is because the absorption torque of the main pump 14 temporarily exceeds the actual torque of the engine 11. This is because the torque limit value T ″, which is a comparison with the case where the fluctuation suppression unit E3 is present "_limitThe flow rate command value Q, that is, the actual discharge rate of the main pump 14, is larger when input to the flow rate command calculation unit E4. This sharp increase in the actual discharge rate of the main pump 14 is at the required flow rate Q^*The same may also occur when directly used as the flow rate command value Q.

Therefore, in the example of fig. 4, the controller 30 (flow rate command calculation unit E4) passes the torque limit value T calculated by the fluctuation suppression unit E3 "_limitThe flow rate command value Q is determined, whereby a sharp increase in the actual discharge rate of the main pump 14 is suppressed. As a result, the controller 30 can be as shown in FIG. 4The engine speed is maintained as indicated by the solid line of (B) in fig. 4, and a large drop in the engine speed can be prevented as indicated by the broken line of (B) in fig. 4. This is because controller 30 can prevent the absorption torque of main pump 14 from exceeding the actual torque of engine 11.

Next, the effect of the fluctuation suppression processing by the controller 30 including the other fluctuation suppression unit E3 will be described with reference to fig. 5. Fig. 5 shows the time-dependent change of the value related to the fluctuation suppression processing when the boom raising operation is performed, similarly to fig. 4. Specifically, fig. 5 includes fig. 5 (a) and fig. 5 (B). Fig. 5 (a) shows a change in the value relating to the torque with time. The torque-related value includes an allowable torque T_limitAnd torque limit value T'_limit. Fig. 5 (B) shows the change in the engine speed with time.

In the example of fig. 5, the fluctuation suppression unit E3 is configured to be based on the target rotation speed ω of the engine 11^*Determining the torque limit value T' from the difference Delta omega between the actual speed omega "_limit。

Target rotational speed ω of engine 11^*For example, the rotation speed is higher than the current engine rotation speed by a rotation speed difference corresponding to an additional load so as to provide the engine 11 with the additional load of a degree that the additional load does not become an overload.

Specifically, fluctuation suppression unit E3 receives allowable torque T calculated by torque limitation unit E2_limitTarget rotational speed ω^*And an actual rotation speed ω detected by an engine rotation speed sensor (not shown) as an input, and calculates a torque limit value T using equation (4) "_limit. In addition, the coefficient K_PIs a proportionality constant, coefficient K_IIs an integration constant.

[ numerical formula 4]

T″_limit＝(ω^*-ω)×K_P+∫(ω^*-ω)dt×K_I

＝Δω×K_P+∫Δωdt×K_I ……(4)

More specifically, the broken line in fig. 5 (a) represents the allowable torque T_limitThe solid line of (a) of fig. 5 represents the torque limit value T calculated using equation (4) as a function of time "_limitChange over time. The broken line in fig. 5 (B) indicates that the fluctuation suppression unit E3 is not present, that is, the torque limit value T is replaced "_limitWhile allowing the torque T_limitThe change over time in the engine speed when input to the flow rate command calculation unit E4. The solid line in fig. 5 (B) indicates the torque limit value T calculated using the equation (4) when the fluctuation suppressing unit E3 is present "_limitThe change over time in the engine speed when input to the flow rate command calculation unit E4.

At time t1, when the right control lever 26R is operated in the boom raising direction, the control valve 175 moves to block the intermediate bypass line 40, and thus the control pressure detected by the control pressure sensor 19 decreases. Therefore, the required flow rate Q calculated from the control pressure^*Increasing as the control pressure decreases. On the other hand, the discharge pressure P detected by the discharge pressure sensor 28 follows the required flow rate Q^*The actual discharge amount increases due to the increase in the amount of the ink. Therefore, according to the required flow rate Q^*And the required torque T calculated from the discharge pressure P^*Sharply increased according to the required torque T^*Calculated allowable torque T_limitAnd also sharply increases as shown by the broken line in fig. 5 (a).

Also, when there is no fluctuation suppression portion E3, that is, when replacing the torque limit value T "_limitWhile allowing the torque T_limitWhen the engine speed is input to the flow rate command calculation unit E4, the engine speed decreases as indicated by the broken line in fig. 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 the torque limit value T calculated using the equation (4) is smaller than the case where the fluctuation suppressing unit E3 is present "_limitThe flow rate command value Q, that is, the actual discharge rate of the main pump 14, is larger when input to the flow rate command calculation unit E4. This sharp increase in the actual discharge rate of the main pump 14 is at the required flow rate Q^*The same may also occur when directly used as the flow rate command value Q.

Therefore, in the example of fig. 5, the controller 30 determines the torque limit value T ″, which is calculated from the use of equation (4), as in the case of the example of fig. 4 "_limitThe flow rate command value Q is determined, whereby a sharp increase in the actual discharge rate of the main pump 14 is suppressed. As a result, the controller30 can maintain the engine speed as indicated by the solid line in fig. 5 (B), and can prevent the engine speed from greatly decreasing as indicated by the broken line in fig. 5 (B). This is because controller 30 can prevent the absorption torque of main pump 14 from exceeding the actual torque of engine 11. Specifically, this is because the controller 30 uses, as the target rotation speed ω, a rotation speed difference value corresponding to an additional load higher than the current engine rotation speed by an amount that does not cause an overload, for the engine 11^*This enables the absorption torque of the main pump 14 to be increased slowly (rather than rapidly).

As described above, the shovel 100 includes the lower propelling body 1, the upper revolving body 3 rotatably mounted on the lower propelling body 1, the engine 11 mounted on the upper revolving body 3, the main pump 14 as a hydraulic pump driven by the engine 11, and the controller 30 as a control device for controlling the flow rate of the hydraulic oil discharged from the main pump 14. Then, the controller 30 is configured to delay (decrease) the responsiveness of the main pump 14 until the actual torque of the engine 11 rises to a level corresponding to the load when the load of the engine 11 increases.

With this structure, the shovel 100 can 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 effectively increase the absorption torque of the main pump 14, that is, the actual torque of the engine 11. This is because the shovel 100 can predict the delay in the rise of the engine output and restrict the discharge rate of the main pump 14 in advance. That is, this is because the shovel 100 can cope with dynamic changes in the actual torque of the engine 11. Therefore, the shovel 100 can suppress a decrease in the engine speed. As a result, the shovel 100 can improve fuel efficiency. Further, the shovel 100 can reduce the uncomfortable feeling that the operator feels about the rotational speed variation of the engine during operation.

Further, by providing the fluctuation suppressing portion E3, the shovel 100 can prevent the engine load, which is the absorption torque of the main pump 14, from increasing sharply 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.

The controller 30 may be configured to increase the flow rate of the hydraulic oil discharged from the main pump 14 in accordance with an increase in the actual torque of the engine 11 by a method other than the method in the above-described embodiment. For example, the controller 30 may be configured to increase the flow rate of the hydraulic oil discharged from the main pump 14 at an increase rate corresponding to an increase in the actual torque of the engine 11. At this time, the rate of increase in the flow rate of the hydraulic oil discharged from the main pump 14 may be set in advance based on at least one of past data, simulation results, and the like.

The controller 30 may be configured to set the required flow rate Q, which is the flow rate of the hydraulic oil to be discharged from the main pump 14, by a method other than the method in the above-described embodiment^*The increase in the flow rate of the hydraulic oil discharged from the main pump 14 suppresses the increase in the flow rate command value Q.

The controller 30 may be configured to realize the required flow rate Q by a method other than the method in the above-described embodiment^*Required torque T^*To calculate the torque limit value T "_limitAnd according to the torque limit value T'_limitThe flow rate command value Q is calculated.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. The above embodiment can be applied to various modifications, replacements, and the like without departing from the scope of the present invention. Further, the features described in the respective descriptions can be combined as long as no technical contradiction occurs.

For example, in the above-described embodiment, the hydraulic system mounted on the shovel 100 is configured to be able to execute negative control as energy saving control, but may be configured to be able to execute positive control, load sensing control, or the like. When the positive control is adopted, the controller 30 may be configured to calculate the required flow rate Q from the operation pressure detected by the operation pressure sensor 29, for example^*. When the load sensing control is adopted, the controller 30 may be configured to calculate the required flow rate Q from the output of a load pressure sensor that detects the pressure of the hydraulic oil in the actuator and the discharge pressure detected by the discharge pressure sensor 28, for example^*。

Further, in the above-described embodiment, the controller 30 executes the fluctuation suppression processing when the boom raising operation is performed, but the fluctuation suppression processing may be executed when at least one of the boom lowering operation, the arm closing operation, the arm opening operation, the bucket closing operation, the bucket opening operation, the swing operation, the traveling operation, and the like is performed.

In the above embodiment, a hydraulic operation lever provided with a hydraulic pilot circuit is disclosed. For example, in the hydraulic pilot circuit related to the left control lever 26L, the hydraulic oil supplied from the pilot pump 15 to the left control 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 that is opened and closed by the tilting of the left control lever 26L in the arm opening direction. Alternatively, in the hydraulic pilot circuit related to right control lever 26R, the hydraulic oil supplied from pilot pump 15 to right control lever 26R is transmitted to the pilot port of control valve 175 at a flow rate corresponding to the opening degree of the remote control valve that is opened and closed by the tilting of right control lever 26R in the boom-up direction.

However, not only the hydraulic operation lever provided with the hydraulic pilot circuit but also an electric operation lever provided with an electric pilot circuit may be used. At this time, the lever operation amount of the electric lever is input to the controller 30 as an electric signal, for example. Further, an electromagnetic valve is disposed between the pilot pump 15 and the pilot port of each control valve. The solenoid valve is configured to operate in response to an electric signal from the controller 30. With this configuration, when a manual operation using an electric control lever is performed, the controller 30 can move each control valve by increasing or decreasing the pilot pressure by controlling the solenoid valve based on an electric signal corresponding to the lever operation amount.

The present application claims priority based on japanese patent application No. 2019-068992, filed on 29/3/2019, the entire contents of which are incorporated by reference in the present application.

Description of the symbols

1-lower traveling body, 2-slewing mechanism, 2A-hydraulic motor for slewing, 2M-hydraulic motor for traveling, 2 ML-hydraulic motor for left traveling, 2 MR-hydraulic motor for right traveling, 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-restrictor, 19-control pressure sensor, 26-operation device, 28-discharge pressure sensor, 29-operation pressure sensor, 30-controller, 40-intermediate bypass line, 42-parallel line, 75-engine speed adjustment dial, 100-shovel, 171-176-control valve, E1-requested torque calculation section, E2-torque limitation section, E3-fluctuation suppression section, E4-flow rate command calculation section.