Construction machinery

Abstract

To provide a hydraulic shovel capable of reducing operational load upon carrying out crushing operation.SOLUTION: A hydraulic shovel is provided with a work device 6 having a boom 17 provided in a derricking manner on a revolving super structure 3 and a controller 47 controlling supply / discharge of hydraulic oil to a boom cylinder 20 and the like. The boom cylinder 20 is driven to a contraction side by supplying the hydraulic oil to a rod side so as to move the boom 17 downward as well as driven to an extension side by supplying the hydraulic oil to a bottom side so as to move the boom 17 upward. The hydraulic shovel has pressure sensors 80a, 80b detecting pressure on the rod side and the bottom side of the hydraulic cylinder 20 for the boom. The controller 47 makes the boom 17 move downward when the detected pressure on the rod side is lower than a first specific value or the detected pressure on the bottom side is equal to a second specific value or more on the basis of detection results of the pressure sensors 80a, 80b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a construction machine equipped with a working device to which an attachment can be attached. [Background technology]

[0002] Patent Document 1 discloses a hydraulic breaker that includes a tool, a hammer piston that strikes the tool, and a control valve that switches the flow of hydraulic oil to the hammer piston, with an upper chamber above the control valve that communicates with an inlet passage, the upper chamber always communicating with a lower piston chamber in which the lower pressure-receiving surface of the hammer piston is located via a passage, and the upper piston chamber in which the upper pressure-receiving surface of the hammer piston is located communicating with the upper chamber when the valve body of the control valve descends, and that has a configuration in which an adjustment valve is arranged near the control valve to throttle the flow rate of hydraulic oil on its way from the upper piston chamber to an outlet in relation to the difference in pressure with the hydraulic oil flowing into the upper chamber, thereby controlling the pressure in the upper piston chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-185378 Summary of the Invention [Problem to be solved by the invention]

[0004] When the hydraulic breaker described in Patent Document 1 is applied to, for example, a hydraulic excavator, the operator attaches the hydraulic breaker to the tip of a work device equipped with a boom and an arm and performs work to crush the object to be crushed. In this case, the operator must operate the hydraulic breaker while adjusting the boom lowering operation to apply an appropriate load to the object to be crushed. Therefore, the work of crushing the object to be crushed requires advanced operating skills, which places a heavy burden on the operator and causes considerable fatigue.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a construction machine that can reduce the operational burden when performing crushing work. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a construction machine comprising a vehicle body, a working device having a boom mounted on the vehicle body so as to be able to be raised and lowered, a hydraulic actuator for operating the working device, and a controller for controlling the supply and discharge of hydraulic oil to the hydraulic actuator, wherein the hydraulic actuator includes a boom cylinder for driving the boom, and the boom cylinder is supplied with pressure oil to its rod side to drive it in the retracted direction, thereby moving the boom in a lowering direction, and supplied with pressure oil to its bottom side to drive it in the extended direction, thereby moving the boom in a raising direction, the construction machine having a pressure detection device that detects pressure on at least one of the rod side and bottom side of the boom cylinder, and the controller executes boom lowering control to move the boom in the lowering direction based on the detection result of the pressure detection device, when the pressure on the rod side detected by the pressure detection device is less than a first predetermined value or the pressure on the bottom side is equal to or greater than a second predetermined value. [Effects of the Invention]

[0007] According to the present invention, the operational burden when performing crushing work can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view showing the external structure of a hydraulic excavator according to an embodiment of the present invention. [Figure 2] 1 is a circuit diagram showing a hydraulic circuit of a hydraulic drive system provided in a hydraulic excavator. [Figure 3] 4 is a flowchart showing a control procedure executed by a controller. [Figure 4] 10 is a table showing criteria for determining whether or not a blank shot state has occurred. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Fig. 1 is a side view of a hydraulic excavator, which is an example of a construction machine according to this embodiment, and shows a state in which a breaker is attached as an attachment. Note that hereinafter, the front side (left side in Fig. 1), rear side (right side in Fig. 1), left side (near side as you look at the page in Fig. 1), and right side (far side as you look at the page in Fig. 1) of the operator when the hydraulic excavator is in the state shown in Fig. 1 and the operator is seated in the driver's seat will be simply referred to as the front side, rear side, left side, and right side.

[0010] <Overview of hydraulic excavators> In FIG. 1, this hydraulic excavator is equipped with a lower traveling body 2 having left and right crawlers 1L, 1R (however, only 1L is shown), an upper rotating body 3 as a vehicle body rotatably mounted on the upper part of this lower traveling body 2, a swing post 5 attached to a rotating frame 4 forming the basic lower structure of the upper rotating body 3 so as to be rotatable in the horizontal direction about a vertical pin (not shown), a working device 6 including a boom 17 attached to the swing post 5 so as to be able to move up and down, i.e., rotate up and down, a cab 7 provided on the rotating frame 4, and an upper cover 8 that covers most of the part of the rotating frame 4 except for the cab 7.

[0011] The lower traveling body 2 includes a substantially H-shaped track frame 9, drive wheels 10L, 10R (only 10L is shown) rotatably supported on the left and right sides of the track frame 9, left and right traveling hydraulic motors 11L, 11R (only 11L is shown) that drive the drive wheels 10L, 10R, respectively, driven wheels 12L, 12R (only 12L is shown) that are rotatably supported near the front ends of the track frame 9 on the left and right sides and are rotated by the driving force of the drive wheels 10L, 10R via tracks 1L, 1R, respectively, and a soil removal blade 13 that is provided on the front side of the track frame 9 so as to be movable up and down and is moved up and down by a blade hydraulic cylinder (not shown). In addition, a slewing base bearing (slewing ring) 14 is arranged in the center of the lower running body 2, and a slewing hydraulic motor 15 (see Figure 2 described below) that rotates the slewing frame 4 relative to the lower running body 2 is built in near the center of this slewing ring 14.

[0012] The swing post 5 is capable of rotating horizontally relative to the revolving frame 4 via the vertical pin. The swing post 5 is also connected to a swing hydraulic cylinder 16 provided on the revolving frame 4 via a connecting pin (not shown), and the extension and contraction of the swing hydraulic cylinder 16 causes the entire swing post 5 to rotate around a vertical axis, allowing the working device 6 to swing left and right.

[0013] The working device 6 is configured as an articulated type and includes the boom 17 and an arm 18 rotatably connected to the boom 17. Each joint of the working device 6 is provided with an angle sensor as a posture detection device, and in this example, at least a boom angle sensor 90 (see FIG. 2 described later) that detects the angle of the boom 17 relative to the swing post, and an arm angle sensor 91 (see FIG. 2 described later) that detects the angle of the arm 18 relative to the boom 17 are provided. The detection results of these angle sensors 90 and 91 are output to a controller 47 described later.

[0014] An attachment is detachably mounted on the tip side of the arm 18. In this example, the attachment is a breaker 19 (hydraulic breaker, breaking tool) equipped with a chisel 19a, which is rotatably connected to the arm 18. The postures of the boom 17, arm 18, and breaker 19 are changed by a boom hydraulic cylinder 20 (boom cylinder), an arm hydraulic cylinder 21 (arm cylinder), and an attachment hydraulic cylinder 22, which serve as hydraulic actuators, respectively. The operation of the breaker 19, which repeatedly pushes and pulls back the chisel 19a, is performed by a hydraulic motor for the breaker (not shown).

[0015] The operator's cab 7 is provided on the left side of the revolving frame 4, and has a driver's seat 25 where the operator sits, a roof 26 provided above the driver's seat 25, and a support 27 that supports the roof 26.

[0016] On the left side of the driver's seat 25 where the operator sits in the driver's cab 7, there is provided a left manual operation lever 37L which, when operated to the left or right, drives the swing hydraulic motor 15 to swing the upper swing body 3 to the left or right, and which, when operated to the front or rear, drives the arm hydraulic cylinder 21 to rotate the arm 18 to the push side (left side in Figure 1) or pull side (right side in Figure 1).

[0017] In addition, a right manual operation lever 37R (see Figure 2 described below) is provided on the right side of the driver's seat 25. When operated left or right, the hydraulic cylinder 22 for the attachment is driven to rotate the breaker 19 to the pull side or push side, and when operated forward or backward, the hydraulic cylinder 20 for the boom is driven to lower or raise the boom 17.

[0018] The upper cover 8 houses therein such equipment as an engine 40 (see FIG. 2 described later), a hydraulic pump 41 (see FIG. 2 described later) driven by the engine 40, a fuel tank that stores fuel for the engine 40, and a hydraulic oil tank (not shown) that serves as a source of pressurized oil for the hydraulic pump 41.

[0019] <Hydraulic circuit> FIG. 2 is a circuit diagram showing a hydraulic circuit of the hydraulic drive system provided in the hydraulic excavator according to this embodiment.

[0020] The hydraulic drive system shown in FIG. 2 is provided with the hydraulic pump 41, the swing hydraulic motor 15, the boom hydraulic cylinder 20, the arm hydraulic cylinder 21, and the attachment hydraulic cylinder 22, which are driven by pressure oil discharged from the hydraulic pump 41, and a swing control valve 42, a boom control valve 43 (pilot control valve), an arm control valve 44, and an attachment control valve 45 (attachment control valve) which control the flow rate of pressure oil supplied from the hydraulic pump 41 to the swing hydraulic motor 15, the boom hydraulic cylinder 20, the arm hydraulic cylinder 21, and the attachment hydraulic cylinder 22, respectively. The hydraulic drive system is also provided with a hydraulic pilot type operating lever device 46L equipped with the left manual operating lever 37L that commands the swinging operation of the upper swing body 3 and the bending operation of the arm 18, a hydraulic pilot type operating lever device 46R equipped with the right manual operating lever 37R that commands the bending operation of the boom 17 and the bending operation of the breaker 19, the pilot pump 38 as a hydraulic source, and a controller 47. The controller 47 is The supply and discharge of hydraulic oil to the swing hydraulic motor 15, the boom hydraulic cylinder 20, the arm hydraulic cylinder 21, and the attachment hydraulic cylinder 22 are controlled via the control valves 42, 43, 44, and 45.

[0021] <Operating lever device> The hydraulic pilot type operating lever device 46L includes the manual operating lever 37L and two pairs of pressure reducing valves 49a, 49b and 50a, 50b that output operating pilot pressure (secondary pilot pressure) that is reduced from the primary pilot pressure from the pilot pump 38 in accordance with the amount of operation in the left-right and front-rear directions, respectively.

[0022] When the operating lever 37L of the operating lever device 46L is operated to the left (or right; the same applies hereinafter to the correspondence in parentheses), the operating pilot pressure generated by the pressure reducing valve 49a (or 49b) according to the amount of operation is output to the pilot operating section 42a (or 42b) of the swing control valve 42 via the pilot line 51a (or 51b). This switches the swing control valve 42 to drive the swing hydraulic motor 15, causing the upper swing body 3 to swing to the left (or right).

[0023] Furthermore, when the operating lever 37L of the operating lever device 46L is operated forward (or rearward; the same applies hereinafter to the correspondence in parentheses), operating pilot pressure generated by the pressure reducing valve 50a (or 50b) according to the amount of operation is output to the pilot operating section 44a (or 44b) of the arm control valve 44 via the pilot pipe line 52a (or 52b). This switches the arm control valve 44, driving the arm hydraulic cylinder 21 in the contraction direction (or extension direction), and rotating the arm 18 to the push side (or pull side).

[0024] The hydraulic pilot type operating lever device 46R includes the manual operating lever 37R and two pairs of pressure reducing valves 53a, 53b and 54a, 54b that output operating pilot pressure reduced from the primary pilot pressure from the pilot pump 38 in accordance with the amount of operation in the left-right and front-rear directions, respectively.

[0025] When the operating lever 37R of the operating lever device 46R is operated to the left (or right; the same applies hereinafter in parentheses), operating pilot pressure generated by the pressure reducing valve 53a (or 53b) in accordance with the amount of operation is output to the pilot operating section 45a (or 45b) of the attachment control valve 45 via the pilot line 55a etc. (or 55b). This switches the attachment control valve 45, driving the attachment hydraulic cylinder 22 in the extension direction (or retraction direction) and rotating the breaker 19 to the pull side (or push side). At this time, a pressure sensor 82 is provided in the line 72a to the bottom side of the attachment hydraulic cylinder 22, which detects the pressure on the bottom side of the attachment hydraulic cylinder 22, and the detection result is output to the controller 47.

[0026] Furthermore, when the operating lever 37R of the operating lever device 46R is operated forward (or rearward; the same applies hereinafter to the correspondence in parentheses), an operating pilot pressure generated by the pressure reducing valve 54a (or 54b) according to the amount of operation is output to the pilot operating section 43a (or 43b) of the boom control valve 43 via the pilot pipe line 56a (or 56b). This switches the boom control valve 43, supplying pressure oil to the rod side of the boom hydraulic cylinder 20 to drive the boom hydraulic cylinder 20 in the retracting direction and move the boom 17 in the lowering direction, or supplying pressure oil to the bottom side of the boom hydraulic cylinder 20 to drive the boom hydraulic cylinder 20 in the extending direction and move the boom 17 in the raising direction. At this time, a pressure sensor 80a (bottom-side pressure detection device) that detects the pressure on the bottom side of the boom hydraulic cylinder 20 is provided in the pipe line 70a to the bottom side of the boom hydraulic cylinder 20. Similarly, a pressure sensor 80b (rod-side pressure detection device) that detects the pressure on the rod side of the boom hydraulic cylinder 20 is provided in the pipe 70b to the rod side of the boom hydraulic cylinder 20. The detection results of these pressure sensors 80a, 80b (pressure detection devices) are output to the controller 47.

[0027] <Solenoid proportional valve> A boom-lowering electromagnetic proportional valve 57 is provided in a pilot line 56b that connects the pressure-reducing valve 54b of the operating lever device 46R and the pilot operation unit 43b of the boom control valve 43. The boom-lowering electromagnetic proportional valve 57 is, for example, normally in a non-communicating state, and when a command signal is sent from the controller 47 to the solenoid unit 57a, the boom-lowering electromagnetic proportional valve 57 reduces the pilot pressure from the pressure-reducing valve 54b to generate a pilot pressure corresponding to the control value of the command signal and outputs it to the pilot operation unit 43b.

[0028] <Features of the embodiment> The boom lowering control executed during crushing work, which is a feature of this embodiment, will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the control procedure executed by the controller 47.

[0029] <Control flow> 3, first, in S10, it is determined whether or not "breaker" has been selected as the work mode of the hydraulic excavator. That is, in this embodiment, a plurality of modes, such as "excavation," "breaker," "vibro hammer," etc., are prepared in advance as work modes of the hydraulic excavator, and the operator can select one of them by operating the operation panel 85 (see FIG. 2) connected to the controller 47. If "breaker" has been selected, the determination is Yes, and the process proceeds to S20.

[0030] In S20, it is determined whether the boom lowering control selector switch 60 (selector switch; see FIG. 2) is ON. That is, in this embodiment, the operator can select whether the boom lowering control is enabled or disabled by turning this boom lowering control selector switch 60 ON or OFF. The selection result of the boom lowering control selector switch 60 is input to, for example, the controller 47. If it is ON, a Yes determination is made and the process proceeds to S30, which will be described later. If it is OFF, a No determination is made and the process returns to S10, where the same procedure is repeated. The boom lowering control selector switch 60 is provided, for example, on the right manual operation lever 37R. Alternatively, it may be provided in a console box (not shown) provided beside the driver's seat 25, separate from the operation lever. Alternatively, it may be provided on the operation panel 85.

[0031] In S30, the posture of the hydraulic excavator is calculated by a known method based on the detection results of the boom angle sensor 90, the arm angle sensor 91, etc., and further, based on the calculated posture, it is determined whether or not the position of the rod in at least one of the boom hydraulic cylinder 20 and the arm hydraulic cylinder 21 is within a stroke end region (for example, set in advance and stored in the controller 47), which is a predetermined range near the stroke end. The technical significance of this determination is as follows. That is, when a breaking operation is performed with the breaker 19 attached to the working implement 6, a reaction force from the object to be broken acts on the chisel 19a of the breaker 19, and the resulting impact also extends to the boom hydraulic cylinder 20, arm hydraulic cylinder 21, and other components provided on the working implement 6. If the impact is applied when the rods of the boom hydraulic cylinder 20 and arm hydraulic cylinder 21 are positioned at or near the stroke end, the resulting mechanical impact may damage the boom hydraulic cylinder 20 and arm hydraulic cylinder 21, potentially reducing their durability. Note that instead of (or in addition to) the boom angle sensor 90 and arm angle sensor 91 described above, a stroke sensor that detects the cylinder stroke amount of the boom hydraulic cylinder 20, arm hydraulic cylinder 21, etc. may be used as the attitude detection device, and it may be determined whether or not the object is within the stroke end region based on the detection results.

[0032] If the piston is within the stroke end region, the determination is Yes and the process proceeds to S34, which will be described later. If the piston is not within the stroke end region, the determination is No and the process proceeds to S35.

[0033] In S35, the control enters a mode that enables the breaker 19 to perform a breaking operation (i.e., a mode that enables operation of a slide switch 62, which will be described later; hereinafter, simply referred to as the "breaking mode") . That is, unlike the mode in S34, which will be described later, the command signal can be output to a solenoid of a breaker drive electromagnetic proportional valve (not shown), which controls the supply and discharge of hydraulic oil to the breaker hydraulic motor. The control value of the command signal at this time can be set by the operator using the attachment slide switch 62 (see FIG. 2) connected to the controller 47. That is, the amount of hydraulic oil supplied to the breaker hydraulic motor via the breaker drive electromagnetic proportional valve is variably set depending on the amount of operation of the slide switch 62 by the operator. As a result, the operator can variably adjust the operation of the breaker 19 (e.g., the frequency of repeated chisel push-out and pull-back operations, or the amount of push-out and pull-back, etc.) based on the amount of operation of the slide switch 62. Then, the control proceeds to S50.

[0034] In S50, it is determined whether the breaker 19 is being operated. Specifically, it is determined whether the attachment slide switch 62 is ON (a position other than the 0 setting) and whether the pressure on the bottom side of the attachment hydraulic cylinder 22 detected by the pressure sensor 82 is equal to or greater than a predetermined value. This is because the operator's intention to operate the breaker 19 can be identified when the attachment slide switch 62 is ON, and a certain level of pressure on the bottom side of the attachment hydraulic cylinder 22 indicates that the breaker 19 is actually rotating in the pull direction. If the above two conditions are not met, it is determined that the breaker 19 is not being operated, S50 is determined as No, and the process returns to S10 and the same procedure is repeated. If the above two conditions are met, it is determined that the breaker 19 is being operated, S50 is determined as Yes, and the process proceeds to S60. Note that the determination in S50 may simply be whether the attachment slide switch 62 is ON (a position other than the 0 setting).

[0035] In S60, it is determined whether the chisel 19a of the breaker 19 is not in contact with the object to be crushed, i.e., whether the state is a so-called blank hitting state. The table showing the criteria for this determination is shown in Fig. 4. As shown in Fig. 4, the determination of whether the state is a blank hitting state is made based on the pressure values ​​detected by the pressure sensors 80a and 80b described above. That is, in this example, it is determined that the blank firing state exists when the pressure on the rod side of the boom hydraulic cylinder 20 detected by the pressure sensor 80b is less than 3 [MPa] (first predetermined value) or the pressure on the bottom side of the boom hydraulic cylinder 20 detected by the pressure sensor 80a is 1 [MPa] (second predetermined value) or more. Conversely, it is determined that the blank firing state does not exist when the pressure on the rod side detected by the pressure sensor 80b is 3 [MPa] or more or the pressure on the bottom side detected by the pressure sensor 80a is less than 1 [MPa]. Furthermore, depending on which of the above is used as the determination criterion, only one of the pressure sensors 80a, 80b may be provided and the above determination may be made based on the detection value of that one pressure sensor. Alternatively, it may be determined that the hydraulic cylinder 20 is in an idle state when the pressure on the rod side of the hydraulic cylinder 20 for the boom detected by the pressure sensor 80b is less than 3 [MPa] (first predetermined value) and the pressure on the bottom side of the hydraulic cylinder 20 for the boom detected by the pressure sensor 80a is 1 [MPa] (second predetermined value) or more. The above-mentioned numerical values ​​are merely examples, and may be set to other values ​​as appropriate depending on the type and specifications of the hydraulic excavator, the work implement 6, and the breaker 19.

[0036] The technical significance of the above-described determination method is as follows: When performing crushing work with the breaker 19 attached to the tip of the working implement 6, if the bottom side pressure of the boom hydraulic cylinder 20 is low and the rod side pressure is high, it is highly likely that the breaker 19 is receiving a reaction force from the object to be crushed, causing the entire working implement 6 to momentarily rise up, i.e., that this is a normal state and not a blank strike. Conversely, if the bottom side pressure of the boom hydraulic cylinder 20 is high and the rod side pressure is low, it is highly likely that the boom 17 is raised too high and the chisel 19a at the tip of the breaker 19 has not reached the object to be crushed, i.e., that this is a blank strike.

[0037] If it is determined that the system is not in an idle-fire state (S60: No), the system proceeds to S80, which will be described later. If it is determined that the system is in an idle-fire state (S60: Yes), the system proceeds to S70. In S70, as the boom-lowering control described above, a command signal is output to solenoid unit 57a to drive boom-lowering electromagnetic proportional valve 57 in an opening direction. As a result, as described above, the pilot pressure generated by boom-lowering electromagnetic proportional valve 57 in accordance with the control value of the command signal is directed to pilot operation unit 43b, boom control valve 43 is switched to the switching position at the right end in FIG. 2, hydraulic oil from hydraulic pump 41 is supplied to the rod side of boom hydraulic cylinder 20 via conduit 70b, and boom 17 moves in the lowering direction.

[0038] Note that the control value in S70, in other words, the drive amount of the boom-lowering electromagnetic proportional valve 57, may be a fixed value, but may also be changeable to a different value for each operator, for example. In this case, as shown in FIG. 2, for example, an operator-specific setting unit 85A (setting device) is provided on the operation panel 85. The operator manually operates the operation panel 85 as appropriate, and the operator-specific setting unit 85A variably sets the amount of pressure oil supplied to the rod side of the boom hydraulic cylinder 20 via the boom control valve 43, which corresponds to the magnitude of the control value. That is, for example, the opening of the boom-lowering electromagnetic proportional valve 57 increases as the control value of the command signal set by the operator-specific setting unit 85A increases.

[0039] Alternatively, the control values ​​for each of a plurality of operators may be registered and stored in advance in the controller 47, and when an operator on board the hydraulic excavator inputs his / her own identification information (such as an operator ID) on the operation panel 85, the stored control values ​​are automatically read out by the operator-specific setting unit 85A and set as values ​​dedicated to that operator.

[0040] Alternatively, a plurality of control modes having mutually different control values ​​may be set in advance in the controller 47, such as "boom lowering control mode 1", "boom lowering control mode 2", etc., and the operator may select one of the plurality of control modes on the operation panel 85 (or the corresponding control mode may be automatically selected by inputting identification information as described above), so that the control value of the control mode corresponding to the operator is set by the operator-specific setting unit 85A. After S70, the process returns to S10 and the same procedure is repeated.

[0041] On the other hand, in S34, to which the process proceeds when the aforementioned S30 is judged No, the process proceeds to a mode in which crushing work by the breaker 19 is disabled (i.e., a mode in which operation of the slide switch 62, which will be described later, is invalid; hereinafter, simply referred to as the "crushing disabled mode") In other words, unlike the mode in the aforementioned S35, it is not possible to output the command signal to the solenoid portion of the breaker drive electromagnetic proportional valve. In other words, regardless of the operation of the slide switch 62 by the operator, the control value of the command signal to the breaker drive electromagnetic proportional valve is set to 0 (or a small value close to 0). After S34, the process proceeds to S40.

[0042] In S40, the monitor 86 (alarm device; see FIG. 2) connected to the controller 47 outputs a warning display indicating that the piston position is within the stroke end region as described above, in other words, a warning display indicating that the hydraulic excavator is in a posture that does not allow crushing work by the breaker 19 (posture warning display; not shown). Thereafter, the process proceeds to S80.

[0043] In S80, the output of a command signal to the solenoid unit 57a for driving the boom-lowering electromagnetic proportional valve 57 in the opening direction is stopped (or the state in which the signal is not output is maintained). As a result, unlike the above, the pilot pressure generated by the boom-lowering electromagnetic proportional valve 57 is not led to the pilot operation unit 43b. As a result, the boom control valve 43 is switched to the neutral position in the center of FIG. 2 or the switch position at the left end in FIG. 2, so that hydraulic oil is not supplied to the rod side of the boom hydraulic cylinder 20 and the boom 17 is not operated in the lowering direction, as in the control in S70 above. After S80, the process returns to S10, and the same procedure is repeated.

[0044] <Effects of the embodiment> As described above, in this embodiment, the pressure sensors 80b, 80a detect the pressures on the rod side and bottom side of the boom hydraulic cylinder 20 that drives the boom 17 provided on the working implement 6. When the breaker 19 is attached to the working implement 6 and a crushing operation is being performed, the controller 47 determines whether the breaker 19 is in an idle-strike state based on the detection results of the pressure sensors 80a, 80b (S60). At this time, the controller 47 determines that the breaker 19 is in an idle-strike state if the pressure on the rod side of the boom hydraulic cylinder 20 is less than a first predetermined value (3 MPa in the above-mentioned example) or if the pressure on the bottom side is equal to or greater than a second predetermined value (1 MPa in the above-mentioned example) (see S60 and FIG. 4). If the controller 47 determines that the breaker 19 is in an idle-strike state, it executes boom-lowering control and moves the boom 17 in the lowering direction via the boom control valve 43 (S70). As a result, even if a blank shot state occurs during crushing work, the controller 47 automatically lowers the boom 17 to eliminate the blank shot state. Therefore, it is no longer necessary for the operator to manually lower the boom and adjust the load in order to prevent a blank shot state, which reduces the operational burden on the operator.

[0045] In particular, when the controller 47 determines that the state is an empty shot state when the pressure on the rod side is less than the first predetermined value and the pressure on the bottom side is equal to or greater than the second predetermined value (see S60 and Figure 4), it is possible to prevent the controller 47 from erroneously determining that the state is an empty shot state when in fact it is not.

[0046] Furthermore, in this embodiment, in particular, a boom lowering control selector switch 60 is provided that switches between enabling and disabling the boom lowering control. This allows the operator, during crushing work, to select whether or not to execute the boom lowering control by the controller 47, as appropriate, depending on the type of work or the operator's own judgment. In this case, because the boom lowering control selector switch 60 is provided on the control lever 37R, the operator can use the boom lowering control selector switch 60 to switch between executing and disabling the boom lowering control while operating the work implement 6 using the control lever 37R. As a result, convenience for the operator can be improved.

[0047] Furthermore, particularly in this embodiment, when the controller 47 determines that the machine is in a blank strike state as described above, a command signal to open the boom-lowering electromagnetic proportional valve 57 is output from the controller 47 as boom-lowering control. The boom-lowering electromagnetic proportional valve 57 is provided in the pilot line 56b that drives the boom control valve 43 in the lowering direction, and opening the boom-lowering electromagnetic proportional valve 57 drives the boom control valve 43 in the boom-lowering direction, thereby operating the boom 17 in the lowering direction.

[0048] Furthermore, particularly in this embodiment, an operator-specific setting section 85A is provided on the operation panel 85, and the drive amount of the boom-lowering electromagnetic proportional valve 57, in other words, the operation amount for driving the boom control valve 43 in the boom-lowering direction through the pilot pipe 56b, can be set for each operator. This makes it possible to set the strength of the boom-lowering behavior in the boom-lowering control in accordance with the preferences, skills, etc. of each operator, further improving convenience.

[0049] Furthermore, particularly in this embodiment, a boom angle sensor 90, an arm angle sensor 91, etc. are provided at the joints of the articulated working device 6, and based on the detection results of the angle sensors 90, 91, etc., the controller 47 determines whether or not the rod of at least one of the arm hydraulic cylinder 21 and the boom hydraulic cylinder 20 is located in a stroke end region (S30). If it is determined that the rod is located in the stroke end region, the controller 47 disables boom lowering control and disables the operation of the breaker 19 (S34, S80). This makes it impossible to perform crushing work using the breaker 19, thereby preventing damage to the boom hydraulic cylinder 20 and the arm hydraulic cylinder 21 due to reaction force from the material to be crushed.

[0050] Furthermore, particularly in this embodiment, when the controller 47 determines that the rod of at least one of the boom hydraulic cylinder 20 and the arm hydraulic cylinder 21 is located in the stroke end region, it displays a posture warning on the monitor 86 (S40). This makes it possible to notify the operator that crushing work cannot be performed because the rod of the boom hydraulic cylinder 20 or the arm hydraulic cylinder 21 is in the stroke region in the current posture of the hydraulic excavator. Note that instead of the monitor 86, a speaker may be provided as a notification device and the notification may be made by outputting a voice message or a buzzer sound.

[0051] <About the problem to be solved and the effects of the invention> The problems to be solved by the invention and the effects of the invention are not limited to those described above. That is, the present invention may solve problems or achieve effects not described above, or may solve only some of the problems or achieve only some of the effects described above.

[0052] <About shape, values, and structure> Concerning the components illustrated in the embodiments and drawings, the shapes, values, and interrelationships between multiple components can be arbitrarily modified and improved within the scope of the technical concept of the present invention.

[0053] In addition to the above, the methods according to the above embodiments and modifications may be used in appropriate combination.

[0054] Although not specifically illustrated, the present invention can be implemented with various modifications within the scope of the invention. [Explanation of symbols]

[0055] 3 Upper rotating body (car body) 6. Work equipment 17. Boom 18 Arm 19 Breakers (hydraulic breakers, attachments, crushing tools) 19a Chisel 20 Boom hydraulic cylinder (boom cylinder) 21 Hydraulic cylinder for arm (arm cylinder) 22 Hydraulic cylinder for attachments 25 Driver's seat 37R Right manual operation lever 43 Boom control valve (pilot operated control valve) 44 Arm control valve 45 Attachment control valve 47 Controller 56b Pilot Pipe 57 Boom lowering solenoid proportional valve 60 Boom lowering control selector switch (selector switch) 80a Pressure sensor (bottom pressure detection device) 80b Pressure sensor (rod side pressure detection device) 85 Operation Panel 85A Operator-specific setting unit (setting device) 86 Monitor (alarm device) 90 Boom angle sensor 91 Arm angle sensor

Claims

1. The car body and a working device having a boom provided on the vehicle body so as to be capable of moving up and down and capable of mounting a crushing tool; a hydraulic actuator for operating the working device; a controller for controlling the supply and discharge of hydraulic oil to the hydraulic actuator; Equipped with The hydraulic actuator a boom cylinder that drives the boom, The boom cylinder Hydraulic oil is supplied to the rod side to drive it in the contracted direction, thereby moving the boom in the lowering direction, and hydraulic oil is supplied to the bottom side to drive it in the extended direction, thereby moving the boom in the raising direction. In construction machinery, a pressure detection device for detecting pressure on at least one of the rod side and the bottom side of the boom cylinder; The controller When the pressure on the rod side detected by the pressure detection device is less than a first predetermined value, or when the pressure on the bottom side is equal to or greater than a second predetermined value, a boom lowering control is executed to move the boom in a lowering direction. Construction machinery characterized by:

2. 2. The construction machine according to claim 1, the pressure detection device includes a rod-side pressure detection device that detects pressure on the rod side of the boom cylinder, and a bottom-side pressure detection device that detects pressure on the bottom side of the boom cylinder, The controller When the rod-side pressure detected by the rod-side pressure detecting device is less than the first predetermined value and the bottom-side pressure detected by the bottom-side pressure detecting device is equal to or greater than the second predetermined value, the boom lowering control is executed. Construction machinery characterized by:

3. 2. The construction machine according to claim 1, a selector switch for switching between enabling and disabling the boom lowering control; A driver's cab provided in the vehicle body; an operation lever provided in the operator's cab for operating the working device, The changeover switch is provided on the operating lever. Construction machinery characterized by:

4. 2. The construction machine according to claim 1, a pilot control valve that is operated by a pilot pressure guided through a pilot line and controls the flow of hydraulic oil supplied to and discharged from the boom cylinder; an electromagnetic proportional valve that is provided in the pilot line and generates the pilot pressure to be introduced to the pilot control valve based on a command signal output from the controller, wherein the pilot control valve supplies hydraulic oil to the bottom side of the boom cylinder when the electromagnetic proportional valve is driven in an opening direction; The controller As the boom lowering control, the command signal for driving the electromagnetic proportional valve in an opening direction is output to the electromagnetic proportional valve. Construction machinery characterized by:

5. 5. The construction machine according to claim 4, a setting device for setting the magnitude of the control value of the command signal output from the controller, A construction machine characterized in that the electromagnetic proportional valve is configured so that the opening degree increases as the control value of the command signal set by the setting device increases.

6. 2. The construction machine according to claim 1, a posture detection device for detecting the posture of the working device; The working device is an arm rotatably connected to the tip side of the boom and to which the crushing tool is attached, the hydraulic actuator includes an arm cylinder that drives the arm, The controller determining whether or not at least one of the rods of the arm cylinder and the boom cylinder is located in a predetermined stroke end region based on a detection result of the posture detection device; When it is determined that the boom is not positioned in the stroke end region, the crushing implement is made operable and the boom lowering control is made executable; When it is determined that the position is in the stroke end region, the crushing implement is made inoperable and the boom lowering control is made inoperable. Construction machinery characterized by:

7. 7. The construction machine according to claim 6, A driver's cab provided in the vehicle body; an alarm device provided inside the driver's cab, The controller When it is determined based on the detection result of the attitude detection device that at least one rod of the arm cylinder or the boom cylinder is positioned in the stroke end region, the alarm device is caused to output a warning. Construction machinery characterized by:

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