JP2010174574A - Working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working machine capable of controlling an engine rotation speed by judging the lowering state of a working device without attaching a pressure sensor to a vertically moving cylinder of the working device. <P>SOLUTION: The working device is constituted to prevent automatically lowering an engine target rotation speed which is setup at a dial value of an accelerator dial when performing a boom lowering operation during excavation, and constitutes an algorithm with only a minimum of sensors of a pump pressure sensor 43 for detecting the pump pressure and an operation valve sensor 44 for detecting an amount of lowering a boom lever. A controller estimates an amount of lowering the working device by integrating the lowering speed of the working device which is obtained from the amount of lowering operation detected by the operation valve sensor 44, controls by judging that the working device is in the lowering state in the air and lowers the engine target rotation speed less than the initial setup rotation speed when the lowering amount is smaller than the lowering amount of setup value, and sets back the engine target rotation speed to the initial rotation speed setup value when the lowering amount is bigger than the lowering amount of setup value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a work machine that lowers an engine target rotational speed of a pump drive engine from an initial rotational speed setting value when operating the working device to lower the operating device.

  When a boom lowering operation is performed in a hydraulic excavator, there is one that regenerates the flow rate from the head side chamber of the boom cylinder to the rod side chamber and controls the discharge amount from the pump to the boom cylinder (for example, Patent Document 1). reference).

  When performing the boom lowering operation, the negative control pressure for pump capacity control of the center bypass line detected by the pressure sensor exceeds a predetermined value, and the controller automatically reduces the engine speed. (For example, refer to Patent Document 2).

JP-A-10-89317 (first page, FIG. 1) JP 2007-333017 A (first page, FIG. 2)

  In such a control, when control is performed so that the engine speed is unconditionally lowered when a boom lowering operation is entered, even when power is required for the boom lowering operation with the bucket grounded in a digging operation or the like. There is a problem that the power cannot be obtained.

  Further, in order to solve this problem, the holding pressure of the boom cylinder head side chamber or the like is detected by a pressure sensor to determine that the bucket is grounded, and a decrease in engine speed is prevented when the bucket is grounded. However, the addition of the pressure sensor as described above is accompanied by improvements in the sensor mounting structure and wiring, which raises the problem of cost increase. Therefore, the boom is lowered without mounting the pressure sensor on the head side of the boom cylinder. It is desirable to determine

  The present invention has been made in view of the above points, and an object of the present invention is to provide a work machine capable of determining the lowered state of the work device and controlling the engine speed without attaching a pressure sensor to the work device vertical movement cylinder. And

  The invention described in claim 1 includes a machine body on which a pump for supplying a working fluid and an engine for driving the pump are mounted, and a work device mounted on the machine body so as to be vertically movable above and below the grounding position; A single rod type working device vertical motion cylinder that moves the working device up and down, and a head side chamber of the working device vertical motion cylinder when controlling the expansion and contraction of the working device vertical motion cylinder and lowering the working device vertical motion cylinder Control valve having a regenerating means for regenerating the flow rate from the rod to the rod side chamber, an operation valve for piloting this control valve, and the operation device being lowered from the operation state by lowering the work device by this operation valve or in the ground-down state If it is determined that the engine is in the air-lowering state, the target engine speed of the engine that drives the pump Was lower than originally rotational speed setting value is a work machine provided with the controller having a function of controlling to return the engine target rotational speed to the original rotational speed setting value when it is determined that the ground down state.

  According to a second aspect of the present invention, the work machine according to the first aspect further includes an operation valve sensor that detects a lowering operation amount of the operation valve that lowers the work device, and the controller includes a lowering operation amount detected by the operation valve sensor. Engine that drives the pump by determining that the working device is in the air-lowering state if the lowering amount is smaller than the lowering amount setting value by integrating the lowering speed of the working device obtained from The target engine speed is reduced from the initial speed setting value, and if the lowering amount is larger than the lowering speed setting value, it is determined that the working device is in the ground-down state and the target engine speed is returned to the initial speed setting value. It has a function to control.

  According to a third aspect of the present invention, in the work machine according to the first aspect, the operation machine further includes an operation valve sensor that detects at least a lowering operation state of the operation valve that lowers the work device, and the controller has a full lowering operation state of the operation valve. Before the set predetermined time elapses, it is determined that the work apparatus is in the air-lowering state, and the engine target rotation speed of the engine that drives the pump is reduced from the initial rotation speed set value. It is provided with a function of controlling to return the engine target speed to the initial speed setting value by determining that the ground is lowered.

  According to a fourth aspect of the present invention, the work machine according to any one of the first to third aspects further includes a pump pressure sensor that detects a pump pressure discharged from the pump, and the controller is configured so that the work device is in a lowered state in the air. Even if it is determined that there is, it has a function of controlling the target engine speed to return to the initial engine speed setting value when the pump pressure is higher than the pressure setting value.

  According to the first aspect of the invention, the controller determines whether the work device is in the air-lowering state or the ground-down state from the operation state in which the operation device is lowered by the operation valve, and is in the air-lowering state. If the engine speed is determined to be lower than the initial engine speed setting value of the engine that drives the pump, and if it is determined that the engine is in the ground-down state, the engine target engine speed is returned to the initial engine speed setting value. Therefore, without attaching a pressure sensor to the vertical motion cylinder of the work device, an engine that is required when the work device is in the ground-down state by determining the lowered state of the work device from the operation state where the work device is lowered by the operation valve. The rotation speed can be secured.

  According to the second aspect of the present invention, the controller integrates the lowering speed of the working device in the air-lowering state obtained from the lowering operation amount of the operating valve detected by the operating valve sensor, thereby reducing the lowering amount of the working device. Since it can be estimated accurately, the ground contact determination of the working device can be made accurate.

  According to the third aspect of the present invention, the controller determines that the work device is in the ground-down state after a predetermined time has elapsed since the operation valve is fully lowered. Can be made easier.

  According to the invention described in claim 4, even if it is determined that the working device is in the air-lowering state from the operation state of the operation valve, it is necessary by monitoring the pump pressure by the pump pressure sensor. The engine speed can be secured.

It is a logic figure which shows one Embodiment of the control algorithm of the working machine which concerns on this invention. It is an engine characteristic figure which shows the example of control which changes the engine target rotational speed of a working machine same as the above automatically. It is a flowchart which shows the control flow of a working machine same as the above. It is a side view of a working machine same as the above. It is a circuit diagram which shows the control circuit of a working machine same as the above.

  Hereinafter, the present invention will be described in detail with reference to an embodiment shown in FIGS.

  As shown in FIG. 4, a hydraulic excavator 10 as a work machine is provided with an upper swing body 12 as a machine body in a lower traveling body 11 so that the upper swing body 12 can turn, and a work device 13 is mounted on the upper swing body 12. The work device 13 is supported by the upper swing body 12 such that the base end of the boom 14 is pivotably supported in the vertical direction, and a stick 15 is pivotally supported at the tip of the boom 14 so as to be pivotable in the front-rear direction. A bucket 16 is pivotally supported so as to be rotatable inward and outward.

  The work device 13 is moved up and down by a boom cylinder 17 as a single rod type work device vertical movement cylinder that rotates the boom 14 in the vertical direction, and the stick 15 is rotated in the front-rear direction by the stick cylinder 18. The bucket 16 is rotated inward and outward by the bucket cylinder 19.

  FIG. 5 shows a hydraulic circuit that controls the boom cylinder 17. The engine 21 drives the drive pump 22, the idle pump 23, and the pilot pump 24 as pumps, and the operation discharged from the drive pump 22 and the idle pump 23. The hydraulic oil as a fluid is supplied to each actuator control spool installed in the control valve 25.

  The engine 21, the drive pump 22, the idle pump 23, and the pilot pump 24 driven by the engine 21 are mounted on the upper swing body 12 shown in FIG. The working device 13 mounted on the upper swing body 12 can move the bucket 16 up and down above and below the grounding position by the boom cylinder 17.

  As shown in FIG. 5, the hydraulic oil discharged from the drive pump 22 is supplied to a boom cylinder control spool 26 installed in a control valve 25 that controls expansion and contraction of the boom cylinder 17, and this boom cylinder control spool. The direction is controlled and the flow rate is controlled at 26 and supplied to the boom cylinder 17. At this time, the pilot hydraulic pressure discharged from the pilot pump 24 is manually controlled by the operation valve (remote control valve) 27, and the boom cylinder control spool of the control valve 25 is passed through the pilot passage 28 (only one of the two is shown). If the displacement direction and displacement amount of the boom cylinder control spool 26 are pilot-operated by acting on one end portion or the other end portion of the boom 26, the operation direction and the operation speed of the boom cylinder 17 are determined. The operation valve 27 is operated by a lever 27a, and boom raising and boom lowering are determined by the operation direction from the neutral position of the lever 27a.

  The control valve 25 has a regenerating means for regenerating the flow rate from the head side chamber of the boom cylinder 17 to the rod side chamber when the boom cylinder 17 is controlled to lower the working device. That is, when the boom cylinder control spool 26 receives the pilot pressure from the operation valve 27 and is displaced to the boom lowering position shown in FIG. 5, the boom cylinder control spool 26 passes from the drive pump 22 through the passage 31 in the control valve 25. The hydraulic oil supplied to the spool 26 is supplied to the rod side chamber (piston upper chamber) of the boom cylinder 17 through the passage 33 whose pressure upper limit is set by the relief valve 32 by the boom cylinder control spool 26. The return oil extruded from the head side chamber (piston lower chamber) of the boom cylinder 17 into the passage 34 joins the passage 33 via the regeneration spool 35 and the check valve 36 as regeneration means. The regeneration spool 35 is displaced to the position shown in FIG. 5 by the boom lowering pilot pressure from the operation valve 27.

  When the regeneration means functions, a sufficient boom lowering speed can be secured by a sufficient regeneration flow rate that merges with the passage 33 via the regeneration spool 35 and the check valve 36, and the boom cylinder 17 can be utilized by utilizing the load of the working device 13. Therefore, the load on the engine 21 and the drive pump 22 can be reduced.

  The hydraulic excavator 10 includes an accelerator dial 41 that sets an engine target rotational speed, that is, an engine target rotational speed by a dial value, and the engine 21 includes an engine speed sensor 42 that detects an engine rotational speed, that is, an actual engine rotational speed. In addition, a pump pressure sensor 43 that detects the pump pressure discharged from the drive pump 22 is provided in the discharge passage of the drive pump 22, and the operation valve (remote control valve) 27 includes an operation valve sensor 44. The accelerator dial 41, the rotation speed sensor 42, the pump pressure sensor 43, and the operation valve sensor 44 are connected to the machine controller 46a.

  The operation valve sensor 44 detects at least the lowering operation state of the operation valve 27 that lowers the work device 13, and preferably detects the lowering operation amount of the operation valve 27 by detecting the lowering direction angle of the lever 27a with a potentiometer or the like. Is.

  The body controller 46a controls the body of the excavator 10. The body controller 46a performs arithmetic processing based on information input from each sensor to the body controller 46a, and outputs a control signal to the engine controller 46b. The engine controller 46b is connected to an electronic governor 47 that controls the fuel injection amount and fuel injection timing of the engine 21, and the engine speed is controlled by the electronic governor 47.

  The body controller 46a and the engine controller 46b constitute a controller 46, and the controller 46 controls a boom lowering speed securing system employed in the excavator 10.

  In this boom lowering speed securing system, when the boom lowering operation is performed, the piston is lowered by the action of the load acting on the piston of the boom cylinder 17 from the boom 14, and the return oil flowing out from the head side chamber of the boom cylinder 17 is discharged. Since it is regenerated in the rod side chamber, the flow rate of the hydraulic oil supplied from the drive pump 22 to the boom cylinder 17 can be reduced, and the rotational speed of the engine 21 that drives the drive pump 22, that is, the engine speed can be reduced. Then, engine speed reduction / regeneration control is performed to ensure the boom lowering speed by the regeneration flow rate.

  On the other hand, in such a boom lowering speed securing system, if the engine speed automatically decreases unconditionally when the boom lowering lever is operated, the bucket 16 is grounded during the dug operation and the boom lowering power When the bucket 16 is determined to be grounded by the logic algorithm shown in FIG. 1 in order to prevent this, the engine speed is not obtained. The control that automatically reduces the number is canceled (canceled) to prevent the engine speed from decreasing.

  That is, the controller 46 determines whether the work device 13 is in the air-lowered state or the ground-down state from the operation state in which the work device 13 is lowered by the operation valve 27, and determines that the work device 13 is in the air-lowered state. By controlling the electronic governor 47 of the engine 21 that drives the motors 22, 23, 24, the target engine speed set by the dial value of the accelerator dial 41 as shown in FIG. When it is determined that the engine is in the ground-down state, a function is provided for controlling the engine target engine speed to return to the initial engine speed setting value.

  For example, the controller 46 integrates the lowering speed of the working device 13 obtained from the lowering operation amount detected by the operation valve sensor 44 to estimate the lowering amount of the working device 13, and the lowering amount is smaller than the lowering amount set value. Determines that the working device 13 is in the air-lowering state and controls the electronic governor 47 of the engine 21 that drives the pumps 22, 23, 24, and the engine target set by the accelerator dial 41 as shown in FIG. Decrease the rotation speed from the initial rotation speed setting value, and if the reduction amount is larger than the reduction amount setting value, it is determined that the working device 13 is in the ground-down state and the engine target rotation speed is returned to the initial rotation speed setting value. It has a function to control.

  Further, for example, the controller 46 determines that the work device 13 is in the air-lowering state before a predetermined time after the full lowering operation state of the operation valve 27 has been set, and drives the pumps 22, 23 and 24. As shown in FIG. 2, the target engine speed set by the accelerator dial 41 is lowered from the initial speed setting value, and after a predetermined time has elapsed, the work device 13 is in a ground-down state. And a function of controlling to return the engine target rotational speed to the initial rotational speed setting value.

  Further, even when the controller 46 determines that the working device 13 is in the air-lowering state, if the pump pressure of the drive pump 22 is higher than a predetermined pressure set value, the engine target speed is set to the initial speed. It also has a function to control to return to the value.

  Next, the algorithm of the airframe controller 46a will be described with reference to the logic diagram shown in FIG.

  First, the configuration of this logic circuit will be described. The relation between the boom lever lowering amount and the boom lowering amount per unit time (that is, the boom lowering speed) when the working device 13 is in the air lowering state is shown in the operation valve sensor 44. A data table 51 created from measured values is connected, an adder 52 is connected to the data table 51, a switch 53 is connected to the adder 52, and an integrator 54 is connected to the output side of the switch 53. The integrator 54 is connected to the adder 52. A 0-value input device 55 is connected to the switch 53.

  Further, a determination device 56 is connected to the operation valve sensor 44 that detects the boom lever lowering amount, and a cage 57 is further connected. A boom regeneration cancel timer 58 is connected to the cage 57, and the cage 57 The switch 53 is connected to the switch 53, and the switch 53 is switched to the zero value input device 55 side by a signal from the holder 57, so that the integration is paused when the boom lowering lever is returned. The output unit of the switching unit 53 is connected to a determination unit 59 in which a threshold value X is set.

  The output portions of the retainer 57 and the determination device 59 are connected to an AND element 61, and the AND element 61 is connected to one input portion of the OR element 62. A pump pressure sensor 43 that detects the pump pressure is connected to a determiner 64 that sets a threshold value P1, and this determiner 64 is connected to the other input part of the OR element 62, and an output part of the OR element 62 is connected to the engine controller 46b. It is connected.

  Next, the function and effect will be described with reference to the logic circuit shown in FIG.

  The algorithm shown in FIG. 1 prevents the target engine speed set by the dial value of the accelerator dial 41 from automatically lowering from the initial speed setting value when the boom is lowered during excavation. In other words, the algorithm can be configured with only the minimum sensor of the pump pressure sensor 43 for detecting the pump pressure and the operation valve sensor 44 for detecting the boom lever lowering amount.

  Based on the relationship between the boom lowering speed and boom lowering speed, the boom lowering speed corresponding to the lever lowering speed is integrated by the data table 51, adder 52, switch 53 and integrator 54 circuits. When the boom lowering lever determined by the circuit of the determiner 56, the retainer 57, and the boom regeneration cancel timer 58 is returned to the neutral position or the boom raised position, 13 is determined to be in contact with the ground, and the engine speed reduction / regeneration control of the boom lowering speed securing system is canceled for the hold seconds set by the boom regeneration cancellation timer 58, and the dial value is determined by the accelerator dial 41 of the engine 21. The target engine speed should not be lowered from the initial engine speed set value set in.

  However, when the boom lowering lever is continuously lowered, it is not possible to determine when to contact the ground, so the engine target speed is kept lowered.

  Also, once the boom lever 27a has entered the excavation operation with a neutral or raised boom, even when the boom is lowered to dig down, it cannot be determined that the bucket 16 has been clearly lifted into the air. A time is set so that the engine target speed (dial value) does not fall below the initial speed setting value for a certain period of time.

  Furthermore, if the pump pressure is detected by the pump pressure sensor 43 when the drilling continues for more than a certain time, it is determined that the air pressure is not lowered even if the pump pressure rises above the threshold value P1, and the accelerator dial is The engine target speed set with the dial value of 41 should not fall below the initial speed setting value.

  When determining the threshold values X and P1, the engine target speed (dial value) is initially rotated only at the time of return when the load is light in each work, based on the results of analysis of the truck loading work and water averaged data by the operator. The threshold values X and P1 are determined so that the dial-down control is automatically lowered below the set value.

  As described above, since the engine speed reduction / regeneration control of the boom lowering speed securing system is triggered by the boom lowering operation, the boom lowering amount is estimated by the boom lowering lever operation. Judge that 16 is grounded. The controller 46 can accurately estimate the lowering amount of the working device 13 by integrating the lowering speed of the working device 13 in the air-lowering state obtained from the lowering operation amount of the operating valve 27 detected by the operating valve sensor 44. Thus, the ground contact determination of the work device 13 can be made accurate.

  The simplest method for estimating the boom lowering amount is to set the boom full lever state using the time required from the state where the boom 14 is raised to the point when the tip bucket 16 touches the ground as the set time. If it lasts for a few seconds, it is determined that the bucket 16 has touched the ground. In the aerial boom lowering operation before the ground contact, the target engine speed is lowered from the initial rotational speed setting value, and after the ground contact, the target engine speed is decreased. The engine speed reduction control is canceled so that the target engine speed is not lowered below the initial engine speed setting value even when the boom is lowered.

  In short, since the controller 46 determines that the work device 13 is in the ground-down state after a predetermined time has elapsed since the full lowering operation state of the operation valve 27 has been set, the ground determination of the work device 13 can be facilitated. it can.

  As described above, the controller 46 determines whether the work device 13 is in the air-lowering state or the ground-lowering state from the operation state in which the work device 13 is lowered by the operation valve 27, and determines that the work device 13 is in the air-lowering state. When the engine target speed of the engine 21 that drives the pumps 22, 23, and 24 is lowered from the initial rotational speed setting value, and when it is determined that the ground is lowered, the engine target rotational speed is returned to the initial rotational speed setting value. Therefore, without attaching a pressure sensor to the boom cylinder 17, the operating valve sensor 44 determines the lowered state of the working device 13 from the operating state in which the working device 13 is lowered, and the working device 13 is in the ground-down state. The engine speed required sometimes can be secured.

  Also, even when the pump pressure of the drive pump 22 detected by the pump pressure sensor 43 is high, it is determined that the digging state is caused by lowering the boom, and even if the boom is lowered, the engine target speed reduction control of the boom lowering speed securing system is performed. Do not do it.

  As a result, the pump pressure sensor 43 monitors the pump pressure even when the signal from the operation valve sensor 44 is processed and it is determined from the operation state of the operation valve 27 that the work device 13 is in the air-lowering state. Thus, the required engine speed can be secured.

  As described above, since operations such as digging the ground require a boom lowering lever operation, a stable excavation force can be obtained without lowering the engine speed during an operation that requires power, such as digging.

  Next, the control flow of the controller 46 will be comprehensively described with reference to the flowchart shown in FIG. The circled numbers in this figure indicate step numbers.

(Step 1)
The body controller 46a determines whether or not the aerial boom lowering operation is performed based on the detection signal from the pump pressure sensor 43. When the pump discharge pressure is low, it is determined that the boom lowering operation is performed in the air.

(Step 2)
When the airframe controller 46a determines an aerial boom lowering operation, the engine controller 46b performs control so that the engine target rotational speed set by the dial value of the accelerator dial 41 is automatically decreased from the initial rotational speed setting value.

(Step 3)
The body controller 46a determines whether or not the operation amount of the boom lowering lever can be detected by the operation valve sensor 44.

(Step 4)
When the operation valve sensor 44 can detect the boom lowering lever operation amount, the machine controller 46a takes in the lever operation amount.

(Step 5)
The body controller 46a calculates the lowering speed of the boom 14 from the boom lowering lever operation amount.

(Step 6)
The body controller 46a integrates the boom lowering speed to obtain the boom lowering amount L.

(Step 7)
The body controller 46a determines whether or not the boom lowering amount L is larger than the threshold value X, that is, whether or not the bucket 16 is grounded.

(Step 8)
The body controller 46a determines whether or not the boom lowering lever has been returned.

(Step 9)
When the boom lowering amount L is larger than the threshold value X and the boom lowering lever is returned, the automatic lowering control of the engine target rotation speed by the engine controller 46b is canceled and the initial value set by the initial dial value of the accelerator dial 41 is released. Return the target engine speed to the speed setting value.

(Step 10)
This release state is maintained for the set hold seconds, and the target engine speed is maintained.

(Step 11)
The body controller 46a determines whether or not the pump pressure detected by the pump pressure sensor 43 is equal to or higher than the pressure set value P1 even when the boom lowering amount L is smaller than the threshold value X or the boom lowering lever is not returned. Determine whether. When the pump pressure is equal to or higher than the pressure set value P1, it is determined that the excavation is in progress, and the process returns to step 9.

(Step 12)
Returning to step 3, if the operation amount of the boom lowering lever cannot be detected by the operation valve sensor 44, or if the integral calculation function cannot be used, the operator fully operates the operation lever 27a on the boom lowering side.

(Step 13)
The body controller 46a determines whether or not a predetermined time has elapsed by operating the boom lowering full lever. If it is determined that the bucket 16 is grounded after the predetermined time has elapsed, the process returns to step 9. If the pump pressure detected by the pump pressure sensor 43 is equal to or higher than the pressure set value P1 before the predetermined time elapses, it is determined that it is during digging, and the process returns to step 9 via step 11.

  The present invention can be used not only for excavation work by the bucket 16 but also for other work by a hydraulic breaker or the like.

10 work machines
12 Upper revolving body as the aircraft
13 Working device
17 Working device vertical cylinder
21 engine
22 Drive pump as pump
25 Control valve
27 Control valve
35 Playback spool as playback means
43 Pump pressure sensor
44 Operation valve sensor

Claims (4)

An airframe equipped with a pump for supplying a working fluid and an engine for driving the pump;
A working device mounted on this machine so that it can move up and down above and below the grounding position;
A single rod type working device vertical movement cylinder that moves up and down this working device;
A control valve having a regenerating means for regenerating the flow rate from the head side chamber of the working device vertical motion cylinder to the rod side chamber when controlling the expansion and contraction of the working device vertical motion cylinder and lowering the working device vertical motion cylinder;
An operation valve for piloting this control valve;
It is determined whether the working device is in the air-lowering state or the ground-lowering state from the operation state in which the working device is lowered by the operation valve, and when it is determined that the working device is in the air-lowering state, the engine target rotation of the engine that drives the pump And a controller having a function of controlling the engine target speed to return to the initial speed setting value when it is determined that the engine speed is lower than the initial speed setting value and is in a ground-down state. Working machine. An operation valve sensor for detecting a lowering operation amount of the operation valve for lowering the work device is provided.
The controller
The lowering amount of the working device is estimated by integrating the lowering speed of the working device obtained from the lowering operation amount detected by the operation valve sensor. If this lowering amount is smaller than the lowering amount set value, the working device is in the air lowering state. The target engine speed of the engine that drives the pump is reduced below the initial speed setting value, and if the lowering amount is larger than the lowering set value, it is determined that the work device is in the ground-down state and the target engine speed The work machine according to claim 1, further comprising a function of controlling the number to return to the initial rotational speed set value. An operation valve sensor for detecting at least a lowering operation state of the operation valve for lowering the work device;
The controller
Prior to the elapse of a predetermined time after the operation valve is fully lowered, it is determined that the working device is in the air-lowering state, and the target engine speed of the engine that drives the pump is decreased from the initial speed setting value, The work machine according to claim 1, further comprising a function of determining that the work device is in a ground-down state after a lapse of time and returning the target engine speed to the initial speed setting value. It has a pump pressure sensor that detects the pump pressure discharged from the pump,
The controller
Even if it is determined that the working device is in the air-lowering state, it has a function to control the engine target speed to return to the initial speed setting value when the pump pressure is higher than the pressure setting value. The work machine according to any one of claims 1 to 3.

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