Construction machine

Abstract

This construction machine comprises: a flow rate control valve as hydraulic equipment for adjusting a flow rate to be supplied to a hydraulic cylinder that drives a work device; and a control device for controlling the hydraulic cylinder so as to satisfy a condition under which a work tool does not move beyond a target surface. The control device calculates a target speed of the hydraulic cylinder such that the work tool satisfies the condition on the basis of detection information of a detection device that detects the attitude of the work device and information on the target surface. When the target value of the hydraulic equipment corresponding to the calculated target speed is smaller than a lower limit value that can ensure the accuracy of the flow rate control, the control device recalculates a target speed of the hydraulic cylinder such that the work tool satisfies the condition on the basis of a limit speed of the hydraulic cylinder obtained from the lower limit value, and controls the hydraulic equipment with the target value corresponding to the recalculated target speed.

Description

Construction machinery

[0001] The present invention relates to a construction machine, and more particularly to a construction machine that controls a working device driven by a hydraulic actuator so that the working device operates under predetermined conditions.

[0002] Construction machines such as hydraulic excavators include a vehicle body including a revolving body and a working device attached to the revolving body. Driven bodies such as the revolving body and the working device are driven by hydraulic actuators such as hydraulic motors and hydraulic cylinders. The working device is an articulated device configured by rotatably connecting multiple link members, and is configured, for example, by a boom connected to the revolving body so as to be rotatable in the vertical direction, an arm connected to the end of the boom so as to be rotatable in the vertical direction, and a bucket connected to the end of the arm so as to be rotatable in the vertical direction. The boom, arm, and bucket are driven by a boom cylinder, an arm cylinder, and a bucket cylinder, respectively. It is not easy to manually operate the multiple link members that make up the working device to excavate a predetermined area, and an operator is required to have skilled operating techniques.

[0003] One example of a method for facilitating such work is the technology described in Patent Document 1. The area-limiting excavation control device for construction machinery described in Patent Document 1 performs control to slow down the movement of the front equipment (working equipment) in a direction approaching the boundary of the set area by correcting the operation signal of an operating lever device related to the front equipment using a first signal correction means. When the front equipment approaches the boundary of the set area, the movement in the direction approaching the boundary is slowed down, making it possible to move the front equipment along the boundary of the set area. This allows the operator to perform work with high precision and stability, regardless of their level of proficiency in operating techniques.

[0004] However, the technology described in Patent Document 1 has the following problem. When semi-automatically controlling a front device (working device) in response to a command from a control device that corrects the operation signal of a control lever device, it is important that the tip of the front device accurately move along a target trajectory. To achieve this, it is necessary to match the flow rate of pressure oil supplied to the hydraulic actuator that drives the front device with the target flow rate. In the area-limiting excavation control device described in Patent Document 1, the opening of the flow control valve is adjusted by controlling the control pressure (pilot pressure) that drives the flow control valve, thereby controlling the flow rate supplied to the hydraulic actuator. However, even if the opening of the flow control valve can be accurately controlled, if the differential pressure across the flow control valve fluctuates due to load fluctuations in the front device (fluctuations in the load pressure of the hydraulic actuator), the flow rate of pressure oil supplied to the hydraulic actuator via the flow control valve may fluctuate and become unstable.

[0005] As a means for solving such problems, for example, the technology described in Patent Document 2 has been proposed. In the hydrostatic drive system described in Patent Document 2, the flow rate of pressure medium (pressure oil) supplied to a consumer (hydraulic actuator) is controlled by a regulating valve (flow control valve) having a throttling action. The opening amount of the regulating valve is adjusted in accordance with the pressure drop (differential pressure before and after the regulating valve) detected by a pressure sensor so that the volumetric flow rate required by a setting device is supplied to the consumer. This makes it possible to accurately control the flow rate of pressure medium supplied to the consumer without an additional pressure compensator, even if the load pressure of the consumer or the supply pressure of the hydraulic pump fluctuates.

[0006] International Publication No. 1995 / 030059 Japanese Patent Application Laid-Open No. 2014-98487

[0007] When performing control that limits the operation of a working implement (front implement) to a predetermined range (hereinafter referred to as "work implement range limit control"), as in the range limit excavation control device described in Patent Document 1, it is considered to apply the technology described in Patent Document 2, which adjusts the opening area of ​​a flow control valve (adjusting valve) according to the differential pressure before and after the valve, in order to improve the accuracy of flow control for the hydraulic actuator that drives the working implement. If the hydraulic actuator is driven at a low speed during range limit control of the working implement, there is a concern that the accuracy of flow control will decrease. If the accuracy of flow control for the hydraulic actuator decreases, it becomes difficult to accurately control the operation of the working implement. This is due to, for example, the following reasons.

[0008] When the restriction of a flow control valve that controls a flow rate, such as the regulating valve described in Patent Document 2, is defined as an orifice restriction, the flow rate Q passing through the flow control valve is expressed by the following equation (1).

[0009] Q = A × √(2 × ΔP / ρ) × Cd ... Equation (1) where A is the opening area of ​​the flow control valve, ΔP is the differential pressure across the flow control valve, ρ is the density of the hydraulic oil, and Cd is the flow coefficient of the flow control valve.

[0010] In the technology described in Patent Document 2, the opening amount of the flow control valve is controlled by a control pressure (pilot pressure) generated by a pilot control valve corresponding to the control of the electronic control device. If there is an error between the control pressure generated by the pilot control valve and a target control pressure corresponding to the control of the electronic control device, a deviation in the opening amount of the flow control valve occurs accordingly. When the flow control valve is operated under a small flow rate condition to drive the hydraulic actuator at a low speed, as is clear from the above equation (1), the opening area (A) of the flow control valve needs to be controlled within a small range. In this case, an error in the control pressure input to the flow control valve has a significant effect on the flow rate passing through the flow control valve. Therefore, when the hydraulic actuator is operated at a low speed, there is a concern that the accuracy of flow control for the hydraulic actuator will decrease, making it difficult to accurately control the operation of the working device.

[0011] The present invention has been made to solve the above problems, and its object is to provide a construction machine that can accurately control the operation of a working device when controlling the range of the working device, even when the hydraulic actuator is driven at a low speed.

[0012] The present application includes a plurality of means for solving the above-mentioned problems. One example of the present invention is a construction machine including a work device including a work implement, at least one hydraulic actuator that drives the work device, a hydraulic device that can adjust the flow rate of pressure oil supplied to the hydraulic actuator, a control device that controls the hydraulic actuator via the hydraulic device so as to satisfy a condition that the work implement does not move beyond a target plane set as a work target for the work implement, and an attitude detection device that detects the attitude of the work device, wherein the control device calculates, as a target speed, a speed of the hydraulic actuator that causes the work implement to satisfy the condition based on detection information from the attitude detection device and setting information of the target plane, a target value of the hydraulic device corresponding to the determined target speed of the hydraulic actuator, and if the calculated target value of the hydraulic device is smaller than a lower limit value at which an allowable accuracy of flow rate control by the hydraulic device can be ensured, the speed of the hydraulic actuator obtained from the lower limit value is calculated as a limit speed of the hydraulic actuator, the target speed of the hydraulic actuator is recalculated based on the calculated limit speed of the hydraulic actuator so that the working implement satisfies the condition, and the hydraulic device is controlled using the target value of the hydraulic device as a control target corresponding to the recalculated target speed of the hydraulic actuator.

[0013] According to one example of the present invention, when a target value for controlling a hydraulic device that adjusts the flow rate supplied to a hydraulic actuator falls below a lower limit value at which accuracy in flow rate control can be ensured, a target value for the hydraulic device that corresponds to a target speed of the hydraulic actuator recalculated based on a speed limit of the hydraulic actuator calculated using the lower limit value is used as a control target. Therefore, even when the working device is operated by driving the hydraulic actuator at a low speed during range limit control of the working device, it is possible to prevent a decrease in accuracy of flow rate control for the hydraulic actuator and to accurately control the operation of the working device. Other problems, configurations, and effects will become clear from the description of the embodiment below.

[0014] 1 is a side view showing a hydraulic excavator as an example of a construction machine according to a first embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram showing a main configuration (main circuit) of the hydraulic system equipped in the construction machine according to the first embodiment shown in FIG. 1. FIG. 2 is a hydraulic circuit diagram showing a pilot circuit of the hydraulic system equipped in the construction machine according to the first embodiment shown in FIG. 1. FIG. 3 is a block diagram showing the hardware and functional configuration of a control device in the construction machine according to the first embodiment. FIG. 4 is a diagram showing factors that cause a decrease in accuracy of flow rate control in a flow control valve, which is a component of the hydraulic system of the construction machine according to the first embodiment shown in FIG. 5. FIG. 6 is a block diagram showing subdivided processing functions of a flow control valve target opening calculation unit in the control device for the construction machine according to the first embodiment shown in FIG. 6. FIG. 7 is a flowchart showing an example of a control procedure by the control device for the construction machine according to the first embodiment shown in FIG. 7. FIG. 8 is an explanatory diagram showing the operation and effects of the construction machine according to the first embodiment. FIG. 9 is a block diagram showing the hardware and functional configuration of a control device in a construction machine according to a second embodiment of the present invention. FIG. 10 is a diagram showing factors that cause a decrease in accuracy of flow rate control in a hydraulic pump, which is a component of the hydraulic system of the construction machine according to the second embodiment. FIG. 11 is a block diagram showing subdivided processing functions of a pump target flow rate calculation unit in the control device for the construction machine according to the second embodiment shown in FIG. 11.

[0015] Hereinafter, an embodiment of a construction machine of the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator will be described as an example of a construction machine. Note that the front, rear, left, and right directions described in this specification refer to directions as seen from the operator riding on the construction machine.

[0016] First Embodiment First, the configuration of a hydraulic excavator as a construction machine according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a side view showing a hydraulic excavator as an example of a construction machine according to the first embodiment.

[0017] 1, the hydraulic excavator 1 is generally composed of a self-propelled running body 2, a rotating body 3 rotatably mounted on the running body 2, and a working device 4 attached to the rotating body 3 so as to be rotatable in the vertical direction. The running body 2 and the rotating body 3 constitute the body of the hydraulic excavator 1 as a construction machine. The rotating body 3 is configured to rotate relative to the running body 2 by a rotating device including a swing motor 6 (see also FIG. 2 described later) as a hydraulic actuator.

[0018] The traveling body 2 is provided with left and right crawler-type traveling devices 8 (only one is shown). The left and right traveling devices 8 are each driven by a traveling motor 9 (only the left traveling motor is shown) which serves as a hydraulic actuator.

[0019] The revolving unit 3 includes a revolving frame 11 as a support structure rotatably mounted on the running unit 2, a cab 12 installed on the left front side of the revolving frame 11, a counterweight 13 provided at the rear end of the revolving frame 11, and a machinery room 14 provided between the cab 12 and the counterweight 13. The cab 12 is equipped with a driver's seat (not shown) where an operator sits, and operation devices 141 and 142 (see FIG. 3 described below), which will be described later. The counterweight 13 is used to balance the weight of the work device 4. The machinery room 14 houses various devices, such as a prime mover (not shown), hydraulic pumps 31, 32, and 33 (see FIG. 2 described below) and a pilot pump 111 (see FIG. 3 described below), and a control valve block 15 as an assembly of a plurality of directional control valves 36 to 46 and flow control valves 51 to 59, which will be described later.

[0020] The working device 4 is an articulated operating mechanism for performing excavation work and the like, and includes, for example, three link members: a boom 21, an arm 22, and a bucket 23 as a working implement. The base end of the boom 21 is rotatably attached to the front of the revolving unit 3. The base end of an arm 22 is rotatably attached to the tip of the boom 21. The base end of the bucket 23 is rotatably attached to the tip of the arm 22. The boom 21, arm 22, and bucket 23 as driven bodies are driven by a pair of hydraulic actuators: a boom cylinder 25, an arm cylinder 26, and a bucket cylinder 27 (see also FIG. 2 , which will be described later).

[0021] The work device 4 is equipped with inertial measurement units (IMUs) 131, 132, and 133 as detection devices that detect the attitudes and operational states of the boom 21, arm 22, and bucket 23. The IMUs 131, 132, and 133 are respectively installed on link members connected to the boom 21, arm 22, and bucket 23. The revolving unit 3 is equipped with an inertial measurement unit (IMU) 134 that detects the attitude and operational state of the machine including the revolving unit 3, and an inertial measurement unit (IMU) 135 that detects the rotation speed of the revolving unit 3. Each of the IMUs 131, 132, 133, 134, and 135 outputs a detection signal corresponding to the detected value (information related to the attitude and operational state) to a control device 200 (see FIG. 3 , described below), described below. It should be noted that instead of the IMUs 31, 132, and 133, the detection devices for detecting the attitude and operating state of the working device 4 may be configured using an inclination sensor, a rotation angle sensor, a stroke sensor, or the like.

[0022] Next, the configuration of the hydraulic system provided in the construction machine according to the first embodiment will be described with reference to Figures 2 and 3. Figure 2 is a hydraulic circuit diagram showing the main configuration (main circuit) of the hydraulic system provided in the construction machine according to the first embodiment shown in Figure 1. Figure 3 is a hydraulic circuit diagram showing the configuration of the pilot circuit of the hydraulic system provided in the construction machine according to the first embodiment shown in Figure 1.

[0023] 2, the hydraulic excavator 1 is equipped with a hydraulic system 30 that hydraulically drives the driven bodies of the traveling body 2, the rotating body 3, and the work device 4 (see FIG. 1). The hydraulic system 30 is equipped with three main pumps, namely, a first hydraulic pump 31, a second hydraulic pump 32, and a third hydraulic pump 33, and a hydraulic oil tank 34 that stores hydraulic oil.

[0024] The three main pumps 31, 32, and 33 are driven by a prime mover (not shown). The first hydraulic pump 31, the second hydraulic pump 32, and the third hydraulic pump 33 are, for example, variable displacement hydraulic pumps, and each includes a first regulator, a second regulator, and a third regulator that adjust the tilt angle of the swash plate or the inclined axis. The first regulator includes a first command pressure port 31a to which a command pressure is input from a pilot circuit 110 (see FIG. 3 ), which will be described later. The second regulator includes a second command pressure port 32a to which a command pressure PiP2 is input from the pilot circuit 110. The third regulator includes a third command pressure port 33a to which a command pressure is input from the pilot circuit 110.

[0025] A first discharge line 71 of the first hydraulic pump 31 is connected to the hydraulic oil tank 34 via a first center bypass line 72, and is also connected to the hydraulic oil tank 34 via a main relief valve 48 to protect the hydraulic circuit from excessive pressure buildup. Arranged on the first center bypass line 72, in this order from upstream, are the right travel direction control valve 36, the bucket direction control valve 37, the second arm direction control valve 38, the first boom direction control valve 39, and a first center bypass cut valve 61 (hereinafter referred to as the first CB cut valve). The bucket direction control valve 37, the second arm direction control valve 38, and the first boom direction control valve 39 are connected in parallel to a first parallel line 73 branching from a portion of the first center bypass line 72 connecting the right travel direction control valve 36 and the bucket direction control valve 37, via first oil passages 74 and 75, second oil passages 76 and 77, and third oil passages 78 and 79, respectively.

[0026] The right traveling directional control valve 36 controls the flow of pressure oil supplied from the first hydraulic pump 31 to a right traveling motor (not shown) of the pair of traveling motors, and also controls the flow of pressure oil discharged from the right traveling motor to the hydraulic oil tank 34. The bucket directional control valve 37 controls the flow of pressure oil supplied from the first hydraulic pump 31 to the bucket cylinder 27, and also controls the flow of pressure oil discharged from the bucket cylinder 27 to the hydraulic oil tank 34. The second arm directional control valve 38 controls the flow of pressure oil supplied from the first hydraulic pump 31 to the arm cylinder 26, and also controls the flow of pressure oil discharged from the arm cylinder 26 to the hydraulic oil tank 34. The first boom directional control valve 39 controls the flow of pressure oil supplied from the first hydraulic pump 31 to the boom cylinder 25, and also controls the flow of pressure oil discharged from the boom cylinder 25 to the hydraulic oil tank 34. Each of the directional control valves 36 to 39 has pilot ports (not shown) at both ends to which a command pressure (pilot secondary pressure) from a pilot circuit 110 (described later) is input. The first CB cut valve 61 controls the flow of pressure oil discharged from the first hydraulic pump 31 to the hydraulic oil tank 34 via the first center bypass line 72. The first CB cut valve 61 has a pilot port 61a to which a command pressure (pilot secondary pressure) from a pilot circuit 110 (described later) is input.

[0027] A second discharge line 81 of the second hydraulic pump 32 is connected to the hydraulic oil tank 34 via a second center bypass line 82, and is also connected to the hydraulic oil tank 34 via a main relief valve 49 to protect the hydraulic circuit from excessive pressure buildup. On the second center bypass line 82, in order from the upstream side, are arranged the second boom directional control valve 40, the first arm directional control valve 41, the first attachment directional control valve 42, the left travel directional control valve 43, and the second center bypass cut valve 62 (hereinafter referred to as the second CB cut valve). The second boom directional control valve 40, the first arm directional control valve 41, the first attachment directional control valve 42, and the left travel directional control valve 43 are connected in parallel to a second parallel line 83 connected to the second discharge line 81 via first oil lines 84 and 85, second oil lines 86 and 87, third oil lines 88 and 89, and fourth oil line 90, respectively.

[0028] The second boom directional control valve 40 controls the flow of pressurized oil supplied from the second hydraulic pump 32 to the boom cylinder 25, and also controls the flow of pressurized oil discharged from the boom cylinder 25 to the hydraulic oil tank 34. The first arm directional control valve 41 controls the flow of pressurized oil supplied from the second hydraulic pump 32 to the arm cylinder 26, and also controls the flow of pressurized oil discharged from the arm cylinder 26 to the hydraulic oil tank 34. When a first special attachment (not shown), such as a chopper or grapple, is attached instead of or in addition to the bucket 23 (see FIG. 1 ), the first attachment directional control valve 42 controls the flow of pressurized oil supplied from the second hydraulic pump 32 to a first special-purpose hydraulic actuator (not shown) that drives the first special attachment, and also controls the flow of pressurized oil discharged from the first special-purpose hydraulic actuator to the hydraulic oil tank 34. The left traveling directional control valve 43 controls the flow of pressure oil supplied from the second hydraulic pump 32 to the left traveling motor 9 (see FIG. 1) of the pair of traveling motors, and also controls the flow of pressure oil discharged from the left traveling motor 9 to the hydraulic oil tank 34. Each of the directional control valves 40 to 43 has pilot ports (41a, 41b for the first arm directional control valve 41 only shown) at both ends to which a command pressure (pilot secondary pressure) from a pilot circuit 110 (described later) is input. The second CB cut valve 62 controls the flow of pressure oil discharged from the second hydraulic pump 32 to the hydraulic oil tank 34 via the second center bypass line 82. The second CB cut valve 62 has a pilot port 62a to which a command pressure PiC2 (pilot secondary pressure) from the pilot circuit 110 (described later) is input.

[0029] The fourth oil line 90 is connected to the first discharge line 71 of the first hydraulic pump 31 via a connection line 80. A merging valve 65 and a check valve 66 are arranged on the connection line 80. The merging valve 65 controls the supply of pressure oil from the first hydraulic pump 31 from the connection line 80 to the fourth oil line 90, and enables the pressure oil from the first hydraulic pump 31 to merge with the pressure oil from the second hydraulic pump 32 and supply it to the left traveling motor 9. The check valve 66 allows the flow of pressure oil from the connection line 80 to the fourth oil line 90, while preventing the flow of pressure oil from the second parallel line 83 and the fourth oil line 90 to the connection line 80.

[0030] A check valve 67 is disposed in a portion of the second parallel line 83 between the connection point with the third oil line 88 and the connection point with the fourth oil line 90. The check valve 67 allows flow from the second parallel line 83 to the fourth oil line 90, while blocking flow from the connection line 80 to the directional control valves 40, 41, 42 other than the left traveling directional control valve 43.

[0031] A third discharge line 91 of the third hydraulic pump 33 is connected to the hydraulic oil tank 34 via a third center bypass line 92, and is also connected to the hydraulic oil tank 34 via a main relief valve 50 to protect the hydraulic circuit from excessive pressure buildup. On the third center bypass line 92, in order from upstream, are arranged a swing directional control valve 44, a third boom directional control valve 45, a second attachment directional control valve 46, and a third center bypass cut valve 63 (hereinafter referred to as the third CB cut valve). The swing directional control valve 44, the third boom directional control valve 45, and the second attachment directional control valve 46 are connected in parallel to a third parallel line 93 connected to the third discharge line 91 via first oil passages 94 and 95, second oil passages 96 and 97, and third oil passages 98 and 99, respectively.

[0032] The swing directional control valve 44 controls the flow of pressurized oil supplied from the third hydraulic pump 33 to the swing motor 6 and controls the flow of pressurized oil discharged from the swing motor 6 to the hydraulic oil tank 34. The third boom directional control valve 45 controls the flow of pressurized oil supplied from the third hydraulic pump 33 to the boom cylinder 25 and controls the flow of pressurized oil discharged from the boom cylinder 25 to the hydraulic oil tank 34. The second attachment directional control valve 46 controls the flow of pressurized oil supplied to a second special hydraulic actuator (not shown) that drives the second special attachment and controls the flow of pressurized oil discharged from the second special hydraulic actuator to the hydraulic oil tank 34 when a second special attachment (not shown) equipped with a second special actuator (not shown) is attached in addition to the first special attachment instead of or in addition to the bucket 23, or when a second special attachment equipped with two special actuators, first and second, is attached instead of the first special actuator. Each of the directional control valves 44 to 46 has a pilot port (not shown) at each end to which a command pressure (pilot secondary pressure) from a pilot circuit 110 (described later) is input. The third CB cut valve 63 controls the flow of pressure oil discharged from the third hydraulic pump 33 to the hydraulic oil tank 34 via the third center bypass line 92. The third CB cut valve 63 has a pilot port 63a to which the command pressure (pilot secondary pressure) from the pilot circuit 110 (described later) is input.

[0033] Furthermore, first oil lines 74, 75, second oil lines 76, 77, and third oil lines 78, 79, which connect the bucket directional control valve 37, the second arm directional control valve 38, and the first boom directional control valve 39 to the first parallel line 73, respectively, are provided with a bucket flow control valve 51, a second arm flow control valve 52, and a first boom flow control valve 53. The bucket flow control valve 51 controls the flow rate of pressure oil supplied from the first hydraulic pump 31 to the bucket cylinder 27 via the bucket directional control valve 37 (pump port). The second arm flow control valve 52 controls the flow rate of pressure oil supplied from the first hydraulic pump 31 to the arm cylinder 26 via the second arm directional control valve 38. The first boom flow control valve 53 controls the flow rate of pressure oil supplied from the first hydraulic pump 31 to the boom cylinder 25 via the first boom directional control valve 39.

[0034] First oil lines 84, 85, second oil lines 86, 87, and third oil lines 88, 89 connect the second boom directional control valve 40, the first arm directional control valve 41, and the first attachment directional control valve 42 to the second parallel line 83, respectively, and are provided with a second boom flow control valve 54, a first arm flow control valve 55, and a first attachment flow control valve 56. The second boom flow control valve 54 controls the flow rate of pressure oil supplied from the second hydraulic pump 32 to the boom cylinder 25 via the second boom directional control valve 40 (pump port). The first arm flow control valve 55 controls the flow rate of pressure oil supplied from the second hydraulic pump 32 to the arm cylinder 26 via the first arm directional control valve 41. The first attachment flow control valve 56 controls the flow rate of pressure oil supplied from the second hydraulic pump 32 to the first special actuator (not shown) via the first attachment directional control valve 42.

[0035] A swing flow control valve 57, a third boom flow control valve 58, and a second attachment flow control valve 59 are provided in first oil lines 94, 95, second oil lines 96, 97, and third oil lines 98, 99, which connect the swing directional control valve 44, the third boom directional control valve 45, and the second attachment directional control valve 46 to the third parallel line 93, respectively. The swing flow control valve 57 controls the flow rate of pressure oil supplied from the third hydraulic pump 33 to the swing motor 6 via the swing directional control valve 44 (pump port). The third boom flow control valve 58 controls the flow rate of pressure oil supplied from the third hydraulic pump 33 to the boom cylinder 25 via the third boom directional control valve 45. The second attachment flow control valve 59 controls the flow rate of pressure oil supplied from the third hydraulic pump 33 to a second special actuator (not shown) via the second attachment directional control valve 46.

[0036] All of the flow control valves 51 to 59 have the same configuration. In Figure 2, only the configuration of the first arm flow control valve 55 is shown, and the configurations of the other flow control valves 51 to 54 and 56 to 59 are omitted. Here, only the configuration of the first arm flow control valve 55 will be described.

[0037] The first arm flow control valve 55 is, for example, a seat-type flow control valve, which has superior responsiveness characteristics to a spool-type flow control valve. The flow control valve 55 has a seat-type valve element 551 that forms a variable throttle between the second oil passage 86 on the primary side and the second oil passage 87 on the secondary side, a control variable throttle 552 that is provided on the valve element 551 so as to communicate with the primary side (second oil passage 86) of the valve element 551, a pilot line 553 that communicates between the downstream side of the control variable throttle 552 and the secondary side (second oil passage 87) of the valve element 551, and a pilot variable throttle 554 that is arranged on the pilot line 553. The housing incorporating the valve element 551 has a first pressure chamber 555 formed at a connection portion with the second oil passage 86, which is the primary side of the valve element 551 (variable throttle), a second pressure chamber 556 formed at a connection portion with the second oil passage 87, which is the secondary side of the valve element 551 (variable throttle), and a third pressure chamber 557 formed to communicate with the first pressure chamber 555 via a control variable throttle 552. The control variable throttle 552 is connected to the first pressure chamber 555 via an oil passage 558 formed inside the valve element 551, and is configured so that the opening area to the third pressure chamber 557 changes depending on the amount of movement of the valve element 551. The pilot variable throttle 554 has a pilot port 554p to which a command pressure PiFAm1 (pilot secondary pressure) generated in response to a command from the control device 200, which will be described later, is input, and the opening amount is adjusted depending on the pilot pressure input to the pilot port 554p.

[0038] In the flow control valve 55, the movement amount of the valve element 551 is determined by the action of the control variable throttle 552 in accordance with the pilot flow rate passing through the pilot line 553. The pilot flow rate in the pilot line 553 is controlled by the opening amount of the pilot variable throttle 554. Therefore, the movement amount of the valve element 551 can be controlled via the opening amount of the pilot variable throttle 554, which can control the pilot flow rate in the pilot line 553. In other words, the flow control valve 55 is configured to control the flow rate of pressure oil supplied to the first arm directional control valve 41 via the second oil passages 86, 87 in accordance with the opening amount of the pilot variable throttle 554.

[0039] 3, the hydraulic system 30 includes a pilot circuit 110 that controls the operation of the hydraulic pilot-type directional control valves 36-46 and the flow control valves 51-59 (see FIG. 2) and also controls the pump capacity of the hydraulic pumps 31-33 (see FIG. 2). The pilot circuit 110 includes a pilot pump 111 that serves as a pilot hydraulic source. The pilot pump 111 is connected to the hydraulic oil tank 34 via a pilot relief valve 112 that generates pilot primary pressure, and is also connected via a pilot line 114 to electromagnetic proportional pressure reducing valves 113a, 113b, 113c, 113d, and 113e that constitute a solenoid valve unit 113.

[0040] The electromagnetic proportional pressure reducing valve 113a is connected to the second command pressure port 32a of the second regulator of the second hydraulic pump 32, and reduces the discharge pressure (pilot primary pressure) of the pilot pump 111 in response to a command from the control device 200 (described later) to generate a pilot secondary pressure PiP2 as a command pressure. The electromagnetic proportional pressure reducing valves 113b, 113c are connected to the pilot ports 41a, 41b of the first-arm directional control valve 41, and reduce the discharge pressure of the pilot pump 111 in response to a command from the control device 200 to generate pilot secondary pressures PiAm1C, PiAm1D as command pressures. The electromagnetic proportional pressure reducing valve 113d is connected to the pilot port 554p of the pilot variable throttle 554 of the first-arm flow control valve 55, and reduces the discharge pressure of the pilot pump 111 in response to a command from the control device 200 to generate a pilot secondary pressure PiFAm1 as a command pressure. The electromagnetic proportional pressure reducing valve 113e is connected to the pilot port 62a of the second CB cut valve 62, and reduces the discharge pressure of the pilot pump 111 in response to a command from the control device 200 to generate a pilot secondary pressure PiC2 as a command pressure.

[0041] To avoid complicating the explanation, the electromagnetic proportional pressure reducing valves for the command pressure ports 31a, 33a of the regulators of the first hydraulic pump 31 and the third hydraulic pump 33 are not shown in the figure. The electromagnetic proportional pressure reducing valves for the directional control valves 36 to 40 and 42 to 46 other than the first arm directional control valve 41 are also not shown in the figure. The electromagnetic proportional pressure reducing valves for the flow control valves 51 to 54 and 56 to 59 other than the first arm flow control valve 55 are also not shown in the figure. The electromagnetic proportional pressure reducing valves for the CB cut valves 61, 63 other than the second CB cut valve 62 are also not shown in the figure.

[0042] 2 and 3 , a first pressure sensor 121, a second pressure sensor 122, and a third pressure sensor 123 are respectively provided in the first discharge line 71 of the first hydraulic pump 31, the second discharge line 81 of the second hydraulic pump 32, and the third discharge line 91 of the third hydraulic pump 33. The first pressure sensor 121, the second pressure sensor 122, and the third pressure sensor 123 detect the discharge pressure of the first hydraulic pump 31 (pressure upstream of the flow control valves 51 to 53), the discharge pressure of the second hydraulic pump 32 (pressure upstream of the flow control valves 54 to 56), and the discharge pressure of the third hydraulic pump 33 (pressure upstream of the flow control valves 57 to 59). The first pressure sensor 121, the second pressure sensor 122, and the third pressure sensor 123 each output a detection signal corresponding to the detected pressure value to a control device 200 described below.

[0043] A pair of actuator lines 101, 101 connecting the first boom directional control valve 39, the second boom directional control valve 40, and the third boom directional control valve 45 to the boom cylinder 25 are each provided with a pressure sensor 124 that detects the pressure (meter-in pressure and meter-out pressure) of the pressure oil supplied to and discharged from the boom cylinder 25. Each pressure sensor 124 also functions as a pressure sensor that detects the pressure downstream of the boom flow control valves 53, 54, 58. Each pressure sensor 124 outputs a detection signal corresponding to the detected pressure value to the control device 200, which will be described later.

[0044] A pair of actuator lines 102, 102 connecting the second arm directional control valve 38 and the first arm directional control valve 41 to the arm cylinder 26 are each provided with a pressure sensor 125 that detects the pressure (meter-in pressure and meter-out pressure) of the pressure oil supplied to and discharged from the arm cylinder 26. Each pressure sensor 125 also functions as a pressure sensor that detects the pressure downstream of the arm flow control valves 52, 55. Each pressure sensor 125 outputs a detection signal corresponding to the detected pressure value to a control device 200, which will be described later.

[0045] A pair of actuator lines 103, 103 connecting the bucket directional control valve 37 and the bucket cylinder 27 are each provided with a pressure sensor 126 that detects the pressure (meter-in pressure and meter-out pressure) of the pressure oil supplied to and discharged from the bucket cylinder 27. Each pressure sensor 126 also functions as a sensor that detects the pressure downstream of the bucket flow control valve 51. Each pressure sensor 126 outputs a detection signal corresponding to the detected pressure value to a control device 200, which will be described later.

[0046] A pair of actuator lines 104, 104 connecting the swing direction control valve 44 and the swing motor 6 are each provided with a pressure sensor 127 that detects the pressure (meter-in pressure and meter-out pressure) of the pressure oil supplied to and discharged from the swing motor 6. Each pressure sensor 127 also functions as a sensor that detects the pressure downstream of the swing flow control valve 57. Each pressure sensor 127 outputs a detection signal corresponding to the detected pressure value to a control device 200, which will be described later.

[0047] The pressure sensors 121 and 124 constitute pressure sensors that detect a front-to-rear differential pressure of the first boom flow control valve 53. The pressure sensors 121 and 125 constitute pressure sensors that detect a front-to-rear differential pressure of the second arm flow control valve 52. The pressure sensors 121 and 126 constitute pressure sensors that detect a front-to-rear differential pressure of the bucket flow control valve 51. The pressure sensors 122 and 124 constitute pressure sensors that detect a front-to-rear differential pressure of the second boom flow control valve 54. The pressure sensors 122 and 125 constitute pressure sensors that detect a front-to-rear differential pressure of the first arm flow control valve 55. The pressure sensors 123 and 124 constitute pressure sensors that detect a front-to-rear differential pressure of the third boom flow control valve 58. The pressure sensors 123 and 127 constitute pressure sensors that detect a front-to-rear differential pressure of the swing flow control valve 57.

[0048] The hydraulic system 30 is equipped with operating devices including a boom operating lever 141 and an arm operating lever 142 that respectively instruct the operation of the boom 21 and arm 22 as driven bodies. The boom operating lever 141 is capable of switching between the first boom directional control valve 39, the second boom directional control valve 40, and the third boom directional control valve 45, and outputs an operating signal (electrical signal) as instruction information instructing the operation of the boom 21 to the control device 200 described below. The arm operating lever 142 is capable of switching between the first arm directional control valve 41 and the second arm directional control valve 38, and outputs an operating signal (electrical signal) as instruction information instructing the operation of the arm 22 to the control device 200 described below.

[0049] In order to avoid complicating the explanation of the operating devices, the right traveling operation lever that switches the right traveling direction control valve 36, the bucket operation lever that switches the bucket direction control valve 37, the first attachment operation lever that switches the first attachment direction control valve 42, the left traveling operation lever that switches the left traveling direction control valve 43, the swing operation lever that switches the swing direction control valve 44, and the second attachment operation lever that switches the second attachment direction control valve 46 are not shown in the figures.

[0050] The control device 200 controls the hydraulic system 30. The control device 200 is electrically connected to an operation device including the boom operation lever 141 and the arm operation lever 142, and operation signals of the operation levers 141, 142 of the operation device are input to the control device 200. The control device 200 is electrically connected to each of the pressure sensors 121 to 127, and detection signals of the pressure sensors 121 to 123, 124 to 127 are input to the control device 200. The control device 200 is electrically connected to each of the IMUs 131 to 135, and detection signals of the IMUs 131 to 135 are input to the control device 200.

[0051] A target surface setting device 151 is electrically connected to the control device 200. The target surface setting device 151 sets a target surface as a work target for excavation work or the like by the work device 4. The target surface setting device 151 is, for example, a display device having a touch panel that functions as an input device, and outputs setting information of the set target surface to the control device 200.

[0052] The control device 200 controls the pump volume of the second hydraulic pump 32 via the second regulator of the second hydraulic pump 32 by controlling the electromagnetic proportional pressure reducing valve 113a of the pilot circuit 110 in accordance with the operation amounts (instruction information) of the operation devices 141, 142. Similarly, the control device 200 also controls the pump volumes of the first hydraulic pump 31 and the third hydraulic pump 33.

[0053] The control device 200 also controls the electromagnetic proportional pressure reducing valves 113b, 113c and 113d of the pilot circuit 110, thereby controlling the hydraulic pilot type first arm directional control valve 41 and the flow control valve 55. The other directional control valves 37 to 40, 42, 44 to 46 and the corresponding flow control valves 51 to 54 and 56 to 59 are also controlled in a similar manner.

[0054] The control device 200 also controls the electromagnetic proportional pressure reducing valve 113e of the pilot circuit 110, thereby controlling the hydraulic pilot type second CB cut valve 62. The other CB cut valves 61 and 63 are controlled in the same manner.

[0055] Next, the hardware and functional configuration of the control device in the construction machine according to the first embodiment will be described with reference to Figures 4 to 6. Figure 4 is a block diagram showing the hardware and functional configuration of the control device in the construction machine according to the first embodiment.

[0056] 4, control device 200 is configured to be able to execute range restriction control (control that restricts the operation of work device 4 to within a restricted range) that controls hydraulic actuators 6, 25 to 27 so as to satisfy the condition that bucket 23 does not move beyond a target surface set as the work target of bucket 23. This range restriction control is performed by controlling the flow direction of pressure oil supplied to each hydraulic actuator 6, 25 to 27 and the flow direction of working oil discharged from each hydraulic actuator 6, 25 to 27 using each directional control valve 36 to 46, and also by controlling the flow rate (meter-in flow rate) of pressure oil supplied to each hydraulic actuator 6, 25 to 27 via control of each flow control valve 51 to 59.

[0057] However, when the control device 200 controls the range of the working implement 4, and one of the hydraulic actuators 6, 25-27 needs to be driven at a low speed, a situation may arise in which the accuracy of the flow control by the flow control valves 51-59 may be reduced. For example, when performing excavation work using the combined movement of the boom 21 and arm 22, the lift amount of the boom 21 may become very small as the arm 22 approaches a vertical position. In this case, the meter-in flow rate of the boom cylinder 25 becomes small, so the opening amount of the flow control valve must be controlled within a very small range. However, control of the opening amount of the flow control valve is subject to error factors such as those shown in FIG. 5 , which may reduce the accuracy of the flow control. If the accuracy of the flow control by the flow control valve is reduced, the boom 21 may move up and down, making it difficult to maintain accurate operation of the working implement 4, and there is a concern that the working implement 4 may move outside the limited range.

[0058] FIG. 5 is a diagram illustrating factors that reduce the accuracy of flow control in a flow control valve, which is a component of the hydraulic system of the construction machine according to the first embodiment shown in FIG. 2 . Flow control by the flow control valve 55 (one example) is performed as follows. First, the electromagnetic proportional pressure reducing valve 113d (see FIG. 3) generates a command pressure in response to a control command from the control device 200. Second, the valve element of the flow control valve 55 is displaced in response to the command pressure generated by the electromagnetic proportional pressure reducing valve 113d. Finally, the flow rate is controlled in response to the opening amount of the opening shape formed by the valve element. The top diagram in FIG. 5 shows the error range of the generated command pressure relative to the target command pressure of the electromagnetic proportional pressure reducing valve (control command from the control device 200). The middle diagram in FIG. 5 shows the error range of the displacement of the flow control valve relative to the generated command pressure of the electromagnetic proportional pressure reducing valve. The bottom diagram in FIG. 5 shows the error range of the opening area of ​​the flow control valve relative to the displacement of the flow control valve (due to machining errors in the opening shape, etc.). These error factors can reduce the accuracy of flow control when the opening amount of the flow control valve is controlled within a small range.

[0059] Therefore, when performing operations involving hydraulic actuators that need to be driven at low speeds, such as performing excavation work by combined operation of the boom 21 and arm 22 described above, the control device 200 according to this embodiment sets target speeds for both the boom cylinder 25 and the arm cylinder 26 that are equal to or greater than the speed limit during forward and backward movements, including when the arm 22 assumes a vertical position, and operates them at the set target speeds. This prevents unstable operation of the work implement 4 due to a low meter-in flow rate of the boom cylinder 25. This embodiment is characterized in that, when the operation of the swing motor 6 and the bucket cylinder 27 is also subject to operation, target speeds are set that are equal to or greater than the speed limit of the hydraulic actuators 6, 25-27, allowing flow control accuracy to be maintained, in order to accurately control the meter-in flow rates of the hydraulic actuators 6, 25-27 that are subject to operation. In this embodiment, controlling the meter-in flow rates of the hydraulic actuators 6, 25-27 that are subject to operation by controlling the flow rates of the flow control valves 51-59 allows stable operation of the work implement 4 to be maintained even under conditions where the meter-in flow rate is low.

[0060] The control device 200 is configured, for example, by a microcomputer including a storage device 201 including RAM, ROM, etc., and a processing device 202 including a CPU, MPU, etc. The storage device 201 pre-stores programs and various information necessary for controlling the plurality of directional control valves 36-46 and the plurality of flow control valves 51-59, which are used to control the drive of the plurality of hydraulic actuators 6, 25-27, as well as the plurality of hydraulic pumps 31-33. The processing device 202 reads the programs and various information from the storage device 201 as appropriate, and executes processing in accordance with the programs to realize various functions. The control device 200 may be configured by one computer or by multiple computers.

[0061] The control device 200 has, as functional units capable of preventing a decrease in the control accuracy of the meter-in flow rate when the hydraulic actuators 6, 25 to 27 are driven at low speeds, an actuator target speed calculation unit 211, an actuator target flow rate calculation unit 212, a pump target flow rate calculation unit 213, a pump control command calculation unit 214, a flow control valve target opening calculation unit 215, a flow control valve control command calculation unit 216, an actuator final target flow rate calculation unit 217, an actuator speed limit calculation unit 218, a directional control valve target opening calculation unit 219, a directional control valve control command calculation unit 220, a CB cut valve target opening calculation unit 221, and a CB cut valve control command calculation unit 222.

[0062] Based on the detection information from the attitude detection devices 131 to 135, the target plane setting information from the target plane setting device 151, and the operation signals (instruction information) from the operation levers 141 and 142 of the operation devices, the actuator target speed calculation unit 211 calculates, as provisional target speeds, speeds of the hydraulic actuators 6, 25 to 27 such that the revolving unit 3 (machine body) and the work device 4 operate in accordance with the operation of the operation devices 141 and 142 under predetermined conditions. For example, the actuator target speed calculation unit 211 calculates a target speed for the tip of the bucket 23 such that the tip of the bucket 23 does not deviate from the target plane, and calculates target speeds for each hydraulic actuator necessary to achieve the calculated tip target speed. The actuator target speed calculation unit 211 also determines whether the calculated provisional target speeds of the hydraulic actuators 6, 25 to 27 are smaller than a speed limit Va_lim of the hydraulic actuators 6, 25 to 27 (described later) which is the result of calculation by the actuator speed limit calculation unit 218. If the provisionally set target speed is equal to or greater than the speed limit, the provisionally set target speed is set as the target speed for each hydraulic actuator 6, 25 to 27. On the other hand, if the provisionally set target speed is lower than the speed limit, the target speed for each hydraulic actuator 6, 25 to 27 is recalculated using the speed limit of the hydraulic actuator 6, 25 to 27. The calculated target speed Va_t for each hydraulic actuator 6, 25 to 27 is output to the actuator target flow rate calculation unit 212.

[0063] The actuator target flow rate calculation unit 212 calculates a target flow rate Qa_t to be supplied to each of the hydraulic actuators 6, 25 to 27 based on the target speed Va_t of each of the hydraulic actuators 6, 25 to 27, which is the calculation result of the actuator target speed calculation unit 211, and the design specifications of each of the hydraulic actuators 6, 25 to 27 stored in advance in the storage device 201. The calculated target flow rates Qa_t of each of the hydraulic actuators 6, 25 to 27 are output to the pump target flow rate calculation unit 213 and the flow control valve target opening calculation unit 215.

[0064] The pump target flow rate calculation unit 213 calculates the flow rate of pressure oil to be discharged from the hydraulic pumps 31 to 33 as a pump target flow rate Qp_t from the target flow rates Qa_t of the hydraulic actuators 6, 25 to 27, which are the calculation results of the actuator target flow rate calculation unit 212. The calculated pump target flow rate Qp_t is output to a pump control command calculation unit 214.

[0065] The pump control command calculation unit 214 calculates a pump flow command from the pump target flow rate Qp_t, which is the calculation result of the pump target flow rate calculation unit 213, generates an electrical signal corresponding to the pump flow command, and outputs it to the pump electromagnetic proportional pressure reducing valve 113a.

[0066] A flow control valve target opening calculation unit 215 calculates a final target opening Af_Ft of each flow control valve 51 to 59 that can ensure the accuracy of flow control, based on the target flow rate Qa_t of each hydraulic actuator 6, 25 to 27, which is the calculation result of the actuator target flow rate calculation unit 212, the detection value of the pressure sensors 121 to 127 that can detect the differential pressure before and after the corresponding flow control valve 51 to 59, and the limit opening area Af_lim, which is a set value. The calculated final target opening Af_Ft of each flow control valve 51 to 59 is output to an actuator final target flow rate calculation unit 217, and is also output to a flow control valve control command calculation unit 216 when the provisionally set target speed of each hydraulic actuator 6, 25 to 27 in the actuator target speed calculation unit 211 or the recalculated target speed is equal to or greater than a speed limit Va_lim of the hydraulic actuators 6, 25 to 27, which will be described later.

[0067] The calculations of the flow control valve target opening calculation unit 215 are specifically performed by the processing shown in Fig. 6. Fig. 6 is a block diagram showing the subdivided processing functions of the flow control valve target opening calculation unit in the control device for a construction machine according to the first embodiment shown in Fig. 4.

[0068] The flow control valve target opening calculation unit 215 calculates the target opening area of ​​each flow control valve 51-59 through processing by a difference processing unit 215a, a square root processing unit 215b, a coefficient processing unit 215c, and a division processing unit 215d based on a flow calculation formula for the orifice restriction. The difference processing unit 215a performs difference processing by subtracting the meter-in pressure of each hydraulic actuator 6, 25-27, which is the detection value Pmi of each pressure sensor 124, 125, 126, 127, from the discharge pressure of each hydraulic pump 31-33, which is the detection value Ppm of each pressure sensor 121, 122, 123. In other words, the difference processing unit 215a corresponds to processing to calculate the pressure difference ΔP (between the upstream and downstream pressures) between the pressure on the upstream side and the pressure on the downstream side of each flow control valve 51-59. The square root processing unit 215b performs processing to take the square root of the before-and-after differential pressure ΔP of each flow control valve 51-59, which is the processing result of the difference processing unit 215a. The coefficient processing unit 215c performs processing to multiply the processing result √ΔP of the square root processing unit 215b by a coefficient α. The coefficient α is a value that includes all constants such as the flow coefficient in the orifice restriction flow rate calculation formula and the density of the working fluid. The division processing unit 215d performs processing to divide the target flow rate Qa_t of each hydraulic actuator 6, 25 to 27, which is the calculation result of the actuator target flow rate calculation unit 212, by the processing result of the coefficient processing unit 215c. The target opening area Af_t of each flow control valve 51 to 59 is calculated using the orifice restriction flow rate calculation formula by the processing of the series of these difference processing unit 215a, square root processing unit 215b, coefficient processing unit 215c, and division processing unit 215d.

[0069] The flow control valve target opening calculation unit 215 further has a maximum value selection processing unit 215e that selects the maximum value from the target opening area Af_t of each flow control valve 51 to 59 calculated by the processing of the series of processing units 215a, 215b, 215c, and 215d, and the limit opening area Af_lim pre-stored in the storage device 201. The maximum value selection processing unit 215e outputs the maximum value from the target opening area Af_t of each flow control valve 51 to 59 obtained as a result of the calculation and the limit opening area Af_lim of the set value to the actuator final target flow rate calculation unit 217 as the final target opening area Af_Ft of each flow control valve 51 to 59.

[0070] The limit opening area Af_lim corresponds to the minimum opening area at which the accuracy of flow control by each of the flow control valves 51 to 59 can maintain an allowable accuracy. The limit opening area Af_lim is determined, for example, as follows. In the range limit control of the working implement 4, an allowable error is set in advance for control of the toe position of the bucket 23. The allowable error in the drive speed of each of the hydraulic actuators 6, 25 to 27 can be specified corresponding to the allowable error in the position of the bucket 23. The allowable error in the meter-in flow rate of each of the hydraulic actuators 6, 25 to 27 can be specified corresponding to the allowable error in the drive speed of each of the hydraulic actuators 6, 25 to 27. Taking into account the errors shown in FIG. 5 , the minimum value of the opening area of ​​each of the flow control valves 51 to 59 that can achieve the allowable error in the meter-in flow rate of each of the hydraulic actuators 6, 25 to 27 is set as the limit opening area.

[0071] The flow control valve control command calculation unit 216 calculates a flow control valve command according to the final target opening amount Af_Ft of each flow control valve 51 to 59, which is the calculation result of the flow control valve target opening calculation unit 215, and generates an electrical signal according to the flow control valve command and outputs it to each electromagnetic proportional pressure reducing valve 113d for the flow control valve.

[0072] An actuator final target flow rate calculation unit 217 calculates a final target flow rate Qa_Ft for each hydraulic actuator 6, 25-27 based on the final target opening amount Af_Ft of each flow control valve 51-59, which is the calculation result of the flow control valve target opening calculation unit 215, and the detection values ​​of pressure sensors 121-127 that can detect the differential pressure before and after each flow control valve 51-59. For this calculation, for example, an orifice throttle flow rate calculation formula or a preset map is used. The calculated final target flow rate Qa_Ft for each hydraulic actuator 6, 25-27 is output to an actuator speed limit calculation unit 218.

[0073] The actuator speed limit calculation unit 218 calculates, as a speed limit Va_lim, the speed of each hydraulic actuator 6, 25 to 27 according to the final target flow rate Qa_Ft of the hydraulic actuators 6, 25 to 27, which is the calculation result of the actuator final target flow rate calculation unit 217. The calculated speed limit Va_lim of the hydraulic actuators 6, 25 to 27 is output to the actuator target speed calculation unit 211.

[0074] The directional control valve target opening calculation unit 219 calculates a target opening Ad_t of each directional control valve 36 to 46 based on thrust information or pressure information of each hydraulic actuator 6, 25 to 27 obtained from detection values ​​of pressure sensors 124 to 127 capable of detecting the meter-in pressure and meter-out pressure of each hydraulic actuator 6, 25 to 27 and the operation amount (instruction information) of each operating lever 141, 142 of the operating device. The target opening is, for example, a target amount of the meter-out opening out of the meter-in opening and the meter-out opening. For example, a map stored in advance in the storage device 201 is used for this calculation. The target opening Ad_t of each directional control valve 36 to 46 calculated as a result is output to a directional control valve control command calculation unit 220.

[0075] The directional control valve control command calculation unit 220 calculates a directional control valve command corresponding to the target opening Ad_t of each directional control valve 36 to 46, which is the calculation result of the directional control valve target opening calculation unit 219, generates an electric signal corresponding to the directional control valve command, and outputs it to each electromagnetic proportional pressure reducing valve 113 b, 113 c for the directional control valve.

[0076] The CB cut valve target opening calculation unit 221 calculates the target opening Ac_t of each of the CB cut valves 61 to 63 based on the operation amount (instruction information) of each of the operation levers 141, 142 of the operation device. For this calculation, for example, a map stored in advance in the storage device 201 is used. The target opening Ac_t of each of the CB cut valves 61 to 63 as a result of the calculation is output to the CB cut valve control command calculation unit 222.

[0077] The CB cut valve control command calculation unit 222 calculates a CB cut valve command according to the target opening amount Ac_t of each CB cut valve 61 to 63, which is the calculation result of the CB cut valve target opening calculation unit 221, and generates an electrical signal according to the CB cut valve command and outputs it to each electromagnetic proportional pressure reducing valve 113e for the CB cut valve.

[0078] Next, the control procedure of the hydraulic system by the control device for the construction machine according to the first embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the control procedure by the control device for the construction machine according to the first embodiment shown in Fig. 4.

[0079] 7, the control device 200 shown in FIG. 4 first determines whether or not an operation signal has been input from the operation devices 141, 142 (step S10). If it is determined in step S10 that an operation signal has not been input (NO), the control device 200 terminates the calculation process related to the control of the hydraulic pumps 31 to 33, the directional control valves 36 to 46, the flow control valves 51 to 59, and the CB cut valves 61 to 63. On the other hand, if it is determined that an operation signal has been input (YES), the process proceeds to steps S20 and S30.

[0080] In step S20, the control device 200 calculates the target opening Ad_t (e.g., meter-out opening) of each of the directional control valves 36-46 based on information about the load pressure or thrust of each of the hydraulic actuators 6, 25-27 obtained from the detection values ​​of the pressure sensors 124-127 and the operation amounts (instruction information) of the operation devices 141, 142. Furthermore, the control device 200 calculates the target opening Ac_t of each of the CB cut valves 61-63 based on the operation amounts (instruction information) of the operation devices 141, 142.

[0081] In parallel with step S20, the control device 200 calculates the target speed Va_t of each hydraulic actuator 6, 25 to 27 based on the detection signals of the attitude detection devices 131 to 135, the target surface setting information of the target surface setting device 151, and the operation signals (instruction information) of each operating lever 141, 142 of the operating device, so that the rotating body 3 (machine body) and the work device 4 operate in accordance with the operation of the operating devices 141, 142 under specified conditions (step S30).

[0082] Next, the control device 200 calculates a target flow rate Qa_t for each of the hydraulic actuators 6, 25 to 27 from the target speed Va_t for each of the hydraulic actuators 6, 25 to 27, which is the calculation result of step S30 (step S40). Furthermore, the control device 200 calculates a pump target flow rate Qp_t for the hydraulic pumps 31 to 33 from the target flow rate Qa_t for each of the hydraulic actuators 6, 25 to 27, which is the calculation result of step S40, and calculates a final target opening Af_Ft for each of the flow control valves 51 to 59 based on the target flow rate Qa_t for each of the hydraulic actuators 6, 25 to 27, which is the calculation result of step S40, and the limit opening area Af_lim detected by the pressure sensors 121 to 127 and the set value (step S50).

[0083] Next, the control device 200 calculates a final target flow rate Qa_Ft for each hydraulic actuator 6, 25-27 based on the final target opening Af_Ft of each flow control valve 51-59, which is the calculation result of step S50, and the detection values ​​of the pressure sensors 121-127 (step S60). Furthermore, the control device 200 calculates the speed of each hydraulic actuator 6, 25-27 corresponding to the final target flow rate Qa_Ft for each hydraulic actuator 6, 25-27, which is the calculation result of step S60, as a speed limit Va_lim (step S70).

[0084] Next, the control device 200 determines whether the target speed Va_t of each hydraulic actuator 6, 25 to 27, which is the calculation result of step S30, is smaller than the speed limit Va_lim of each hydraulic actuator 6, 25 to 27, which is the calculation result of step S70 (Va_t<Va_lim) (step S80). If the determination in step S80 is YES, the process proceeds to step S90, and steps S40 to S80 are repeated again. On the other hand, if the determination is NO, the process proceeds to step S100, and the series of processes ends.

[0085] If it is determined in step S80 that the target speed Va_t is smaller than the speed limit Va_li (YES), the calculation result of step S30 is discarded, and the target speed Va_t of each hydraulic actuator 6, 25 to 27 is recalculated using the speed limit Va_lim of the hydraulic actuators 6, 25 to 27 that is the calculation result of step S70 (step S90). The recalculation of the target speed Va_t of each hydraulic actuator 6, 25 to 27 is based on the speed limit Va_lim of the hydraulic actuator corresponding to the flow control valve whose limit opening area Af_lim is selected as the final target opening Af_Ft, and the target speeds Va_t of the remaining hydraulic actuators necessary to execute range limit control are recalculated.

[0086] In step S90, the target speed Va_t of each hydraulic actuator 6, 25 to 27 is recalculated using the speed limit Va_lim of the hydraulic actuators 6, 25 to 27, and the processing of steps S40 to S80 is then redone using the recalculated target speed Va_t of each hydraulic actuator 6, 25 to 27. As a result, the pump target flow rate Qp_t of the hydraulic pumps 31 to 33 and the final target opening Af_Ft of each flow control valve 51 to 59 are recalculated taking into account the speed limit Va_lim of the hydraulic actuators 6, 25 to 27 (step S50).

[0087] On the other hand, if it is determined in step S80 that the target speed Va_t is equal to or greater than the speed limit Va_li (NO), a pump flow rate command is calculated from the pump target flow rate Qp_t, which is the result of the calculation or recalculation of step S50, and a command signal is output to the pump electromagnetic proportional pressure reducing valve 113a. Also, a flow control valve command is calculated from the final target openings Af_Ft of each flow control valve 51 to 59, which is the result of the calculation or recalculation of step S50, and a command signal is output to the flow control valve electromagnetic proportional pressure reducing valve 113d (step S100). Also, a directional control valve command is calculated from the target openings Ad_t of each directional control valve 36 to 46, which is the result of the calculation of step S20, and a command signal is output to the directional control valve electromagnetic proportional pressure reducing valves 113b, 113c. Also, a CB cut valve command is calculated from the target openings Ac_t of each CB cut valve 61 to 63, and a command signal is output to the CB cut valve electromagnetic proportional pressure reducing valve 113e (step S100).

[0088] Next, the operation and effects of the construction machine according to the first embodiment will be described with reference to Figures 2 to 4 and Figures 6 to 8. Figure 8 is an explanatory diagram showing the operation and effects of the construction machine according to the first embodiment.

[0089] For ease of explanation, the following describes an example of operation when area restriction control is performed to move the tip of the bucket 23 by the combined operation of the boom 21 and arm 22 shown in Figure 8. In Figure 8, the toe of the bucket 23 is moved in a direction that draws it closer to the machine bodies 2 and 3 with respect to a target plane St indicated by a two-dot chain line. The control device 200 shown in Figure 4 executes area restriction control to control the operation of the boom 21 and arm 22 so that the toe of the bucket 23 does not deviate from the target plane St. In this case, as the arm 22 approaches a vertical attitude, the amount of lift of the boom 21 gradually decreases.

[0090] Specifically, the control device 200 (211) calculates a target speed Vt_t(1) for the tip of the bucket 23 that will prevent the tip of the bucket 23 from deviating from the target surface St, based on the operation signals from the operation devices 141, 142, the detection values ​​of the attitude detection devices 131 to 135, and the setting information for the target surface from the target surface setting device 151. Furthermore, the control device 200 (211) calculates a target speed Vbm_t(1) for the boom cylinder 25 and a target speed Vam_t(1) for the arm cylinder 26 that are required to realize the calculated toe target speed Vt_t(1) (step S30 shown in FIG. 7). These target speeds (indicated by thick dashed arrows in FIG. 8) are provisional settings.

[0091] When the arm 22 approaches a vertical position and the amount of lift of the boom 21 is small, in the calculations of the control device 200 (215) shown in FIG. 6 , the target opening area Af_t of the flow control valves 53, 54, 58 for the boom cylinder 25, which is calculated based on the target flow rate obtained from the target speed Vbm_t of the boom cylinder 25, may become smaller than the limit opening area Af_lim at which flow control accuracy can be ensured. In this case, the control device 200 (215) selects the limit opening area Af_lim as the final target opening area Af_Ft of the flow control valves 53, 54, 58. This makes it possible to ensure accuracy in flow control for the boom cylinder 25 by the flow control valves 53, 54, 58.

[0092] The control device 200 (217, 218) shown in FIG. 4 calculates the speed limit Vbm_lim of the boom cylinder 25 using the limit opening area Af_lim, which is the final target opening area Af_Ft of the flow control valves 53, 54, 58 for the boom cylinder 25, and the detection values ​​of the pressure sensors 121 to 124 (the differential pressure before and after the flow control valves 53, 54, 58).

[0093] The control device 200 (211) recalculates the toe target speed Vt_t(2) based on the speed limit Vbm_lim of the boom cylinder 25 under the condition that the direction of the toe target speed Vt_t(1) of the bucket 23 obtained as a result of the previous calculation is maintained. Furthermore, the control device 200 (211) recalculates the target speed Vbm_t(2) of the boom cylinder 25 and the target speed Vam_t(2) of the arm cylinder 26 required to execute the recalculated toe target speed Vt_t(2). In this case, the target speed Vbm_t(2) of the boom cylinder 25 is the speed limit Vbm_lim of the boom cylinder 25. In FIG. 8 , the recalculated target speeds are indicated by thick solid arrows. Furthermore, the control device 200 (215) recalculates the target opening area Af_t of the flow control valves 52, 55 for the arm cylinder 26 corresponding to the recalculated target speed Vam_t(2) of the arm cylinder 26.

[0094] As described above, in the present embodiment, during range limit control of working implement 4, if the target speed of any of the multiple hydraulic actuators falls below the speed limit, the target speed of each hydraulic actuator is recalculated so as to ensure the accuracy of flow rate control by each flow control valve 51 to 59 while maintaining the movement direction of bucket 23 in accordance with the operation of operation devices 141, 142. This ensures the accuracy of flow rate control for the hydraulic actuators by each flow control valve 51 to 59, allowing the movement of bucket 23 to be accurately controlled.

[0095] As described above, the hydraulic excavator 1 (construction machinery) according to the first embodiment includes the working device 4 including the bucket 23 as a working implement, the boom cylinder 25, arm cylinder 26, and bucket cylinder 27 (at least one hydraulic actuator) that drive the working device 4, flow control valves 51 to 59 that serve as hydraulic equipment that can adjust the flow rate of pressurized oil supplied to the hydraulic actuators 25 to 27, a control device 200 that controls the hydraulic actuators 25 to 27 via the flow control valves 51 to 59 (hydraulic equipment) so as to satisfy the condition that the bucket 23 (working implement) does not move beyond a target surface that is set as a work target of the bucket 23 (working implement), and IMUs 131 to 135 that serve as attitude detection devices that detect the attitude of the working implement 4. The control device 200 calculates the speed of the hydraulic actuators 25 to 27 at which the bucket 23 (work implement) satisfies the above conditions as a target speed Va_t based on the detection information of the IMUs 131 to 135 (posture detection devices) and the setting information of the target plane, calculates target values ​​for the flow control valves 51 to 59 (hydraulic equipment) corresponding to the calculated target speeds Va_t of the hydraulic actuators 25 to 27, and determines whether the calculated target values ​​for the flow control valves 51 to 59 (hydraulic equipment) are smaller than a lower limit value that can ensure an allowable accuracy of flow control by the flow control valves 51 to 59 (hydraulic equipment). In this case, the speeds of the hydraulic actuators 25 to 27 obtained from the lower limit value are calculated as the speed limit Va_lim of the hydraulic actuators 25 to 27, and the target speeds Va_t of the hydraulic actuators 25 to 27 are recalculated based on the calculated hydraulic actuator speed limit Va_lim so that the bucket 23 (work implement) satisfies the above condition.The flow control valves 51 to 59 (hydraulic equipment) are controlled using the target values ​​of the flow control valves 51 to 59 (hydraulic equipment) as control targets corresponding to the recalculated target speeds Va_t of the hydraulic actuators 25 to 27.

[0096] According to this configuration, when the target value for controlling the flow control valves 51 to 59 (hydraulic equipment) that adjust the supply flow rate to the hydraulic actuators 25 to 27 falls below the lower limit value at which the accuracy of flow rate control can be ensured, the target value of the flow control valves 51 to 59 (hydraulic equipment) that corresponds to the target speed Va_t of the hydraulic actuators 25 to 27, recalculated based on the speed limit Va_lim of the hydraulic actuators 25 to 27 calculated using this lower limit value, is used as the control target.Therefore, even when the working device 4 is operated by driving the hydraulic actuators 25 to 27 at low speeds during range limit control of the working device 4, it is possible to prevent a decrease in the accuracy of the flow rate control for the hydraulic actuators 25 to 27, and it is possible to accurately control the operation of the working device 4.

[0097] Furthermore, in the present embodiment, at least one hydraulic actuator that drives the working implement 4 is made up of multiple hydraulic actuators: a boom cylinder 25, an arm cylinder 26, and a bucket cylinder 27. The target speeds of the hydraulic actuators 25 to 27 in the control device 200 are calculated based on the detection information of the IMUs 131 to 135 (attitude detection devices), target plane setting information, and the movement direction of the bucket 23 (work implement) obtained from instruction information that instructs the operation of the working implement 4. The recalculation of the target speeds of the hydraulic actuators 25 to 27 in the control device 200 is performed based on the calculated speed limit to calculate the speeds of the multiple hydraulic actuators 25 to 27 that satisfy the above conditions while the bucket 23 (work implement) maintains the above movement direction.

[0098] According to this configuration, the target speeds of the multiple hydraulic actuators 25 to 27 are recalculated so that the bucket 23 (work implement) moves in a direction corresponding to instruction information based on the operation of the operating devices 141, 142 and the automatic control of the control device 200, so that the work implement 4 can be operated in accordance with the instructions of the operating devices 141, 142 and the automatic control of the control device 200.

[0099] In this embodiment, the hydraulic devices are flow control valves 51-59 that can control the flow rate of pressure oil supplied to the hydraulic actuators 25-27, and the control device 200 further includes pressure sensors 121-126 that serve as pressure detection devices that detect differential pressure across the flow control valves 51-59. The target values ​​of the hydraulic devices are target opening areas Af_t of the flow control valves 51-59, which are calculated based on the target flow rates Qa_t of the hydraulic actuators 25-27, which are obtained from the calculated target speeds Va_t of the hydraulic actuators 25-27, and the detection values ​​of the pressure sensors 121-126 (pressure detection devices). The lower limit value is a limit opening area Af_lim that is preset for the flow control valves 51-59 depending on the accuracy of the flow control. The control device 200 calculates the speed limit Va_lim of the hydraulic actuators 25-27 based on the flow rate calculated using the limit opening area Af_lim of the flow control valves 51-59 and the detection values ​​of the pressure sensors 121-126 (pressure detection devices).

[0100] According to this configuration, in the operation restriction control of the working implement 4, the operation of the working implement 4 can be accurately controlled by controlling the flow rates of the flow control valves 51 to 59 for the hydraulic actuators 25 to 27.

[0101] The hydraulic excavator 1 (construction machine) according to this embodiment also includes directional control valves 37-42, 45, and 46 that control the flow direction of pressure oil supplied to the hydraulic actuators 25-27 and can control the flow of pressure oil discharged from the hydraulic actuators 25-27. The flow control valves 51-59 are disposed upstream of the directional control valves 37-42, 45, and 46. The pressure detection device includes pressure sensors 124-126 that detect the meter-in pressure and meter-out pressure of the hydraulic actuators 25-27. The control device 200 controls the meter-out openings of the directional control valves 37-42, 45, and 46 based on thrust information or pressure information of the hydraulic actuators 25-27 obtained from the detection values ​​of the pressure sensors 124-126.

[0102] According to this configuration, by controlling the meter-out openings of the directional control valves 37 to 42, 45, and 46 in the operation restriction control of the working device 4, it is possible to prevent the hydraulic actuators 25 to 27 from running away due to the weight of the working device 4 itself.

[0103] [Second Embodiment] Next, a construction machine according to a second embodiment of the present invention will be described using Figures 9 to 12. In Figures 9 to 12, the same reference numerals as those shown in Figures 1 to 8 indicate similar parts, and detailed description thereof will be omitted. Figure 9 is a block diagram showing the hardware and functional configuration of a control device in a construction machine according to the second embodiment. Figure 10 is a diagram showing factors (error factors) that cause a decrease in accuracy of flow rate control in a hydraulic pump, which is a component of the hydraulic system of a construction machine according to the second embodiment.

[0104] The construction machine according to the second embodiment differs from the first embodiment in that, in the range limit control by the control device, the accuracy of flow control for each hydraulic actuator is ensured by limiting the lower limit of the pump flow rate rather than the lower limit of the flow control valve opening. That is, in the construction machine control device 200A according to the second embodiment shown in FIG. 9, the processing contents of the pump target flow rate calculation unit 213A, the flow control valve target opening calculation unit 215A, and the actuator speed limit calculation unit 218A are different from those of the functional units 213, 215, and 218 of the control device 200 of the first embodiment, and the actuator final target flow rate calculation unit 217 of the control device 200 of the first embodiment is unnecessary. Other configurations of the second embodiment are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0105] In the range limiting control of the control device 200A, for example, when it is necessary to drive any one of the hydraulic actuators 6, 25 to 27 independently at low speed, the discharge flow rate of the hydraulic pumps 31 to 33 may become small. In this case, the discharge flow rate of the hydraulic pumps 31 to 33 must be controlled to a very small amount. However, the control of the discharge flow rate of the hydraulic pumps 31 to 33 is subject to error factors as shown in FIG. 10 , and these error factors may reduce the accuracy of the flow rate control for the hydraulic actuators 6, 25 to 27. If the accuracy of the flow rate control decreases, it becomes difficult to maintain accurate operation of the working device 4, and there is a concern that the working device 4 may move outside the limited range.

[0106] The discharge flow rate of the hydraulic pump 32 (see FIG. 2) is controlled as follows. First, the electromagnetic proportional pressure reducing valve 113a (see FIG. 3) generates a command pressure based on a control command from the control device 200A. Second, when the command pressure generated by the electromagnetic proportional pressure reducing valve 113a is input to the command pressure port 32a (see FIG. 2) of the regulator of the hydraulic pump 32 and the tilt of the swash plate or inclined axis of the hydraulic pump 32 changes, the discharge flow rate is controlled in accordance with the tilt of the hydraulic pump 32. The upper diagram in FIG. 10 shows the error range of the generated command pressure relative to the target command pressure of the electromagnetic proportional pressure reducing valve (control command from the control device). The lower diagram in FIG. 10 shows the error range (due to manufacturing errors, etc.) of the discharge flow rate of the hydraulic pump relative to the generated command pressure of the electromagnetic proportional pressure reducing valve. Due to such error factors, the accuracy of flow rate control may be reduced when controlling the discharge flow rate of the hydraulic pump at a very small amount.

[0107] Therefore, a pump target flow rate calculation unit 213A of a control device 200A according to the second embodiment calculates the flow rate to be discharged by the hydraulic pumps 31 to 33 as a pump final target flow rate Qp_Ft based on the limit flow rate Qp_lim, which is a set value, and the target flow rates Qa_t for the hydraulic actuators 6, 25 to 27, which are the calculation results of the actuator target flow rate calculation unit 212. The calculated pump final target flow rate Qp_Ft is output to a pump control command calculation unit 214 and an actuator speed limit calculation unit 218A.

[0108] The calculation of the pump target flow rate calculation unit 213A is specifically performed by the processing shown in Fig. 11. Fig. 11 is a block diagram showing the detailed processing functions of the pump target flow rate calculation unit in the control device for a construction machine according to the second embodiment shown in Fig. 9.

[0109] The pump target flow rate calculation unit 213A has a pump target flow rate calculation processing unit 213b and a maximum value selection processing unit 213c. The pump target flow rate calculation processing unit 213b calculates the target flow rate Qp_t for the hydraulic pumps 31 to 33 by adding up the target flow rates Qa_t for each hydraulic actuator 6, 25 to 27, which are the calculation results of the actuator target flow rate calculation unit 212. The maximum value selection processing unit 213c selects the maximum value from the target flow rates Qp_t for the hydraulic pumps 31 to 33, which are the processing results of the pump target flow rate calculation processing unit 213b, and the limit flow rate Qp_lim pre-stored in the storage device 201. The maximum value selection processing unit 213c outputs the maximum value from the calculation results of the target flow rates Qp_t for the hydraulic pumps 31 to 33 and the set value limit flow rate Qp_lim as the final target flow rate Qp_Ft for the hydraulic pumps 31 to 33 to the pump control command calculation unit 214 and the actuator speed limit calculation unit 218A.

[0110] The limit flow rate Qp_t corresponds to the minimum discharge flow rate at which the accuracy of flow rate control for each hydraulic actuator 6, 25 to 27 can be maintained within an allowable accuracy. The limit flow rate Qp_t is determined, for example, as follows: In the range limit control of the work implement 4, an allowable error is set in advance for control of the toe position of the bucket 23. An allowable error in the drive speed of each hydraulic actuator 6, 25 to 27 can be specified corresponding to the allowable error in the position of the bucket 23. An allowable error in the meter-in flow rate of each hydraulic actuator 6, 25 to 27 can be specified corresponding to the allowable error in the drive speed of each hydraulic actuator 6, 25 to 27. The minimum value of the discharge flow rate of the hydraulic pumps 31 to 33 that can achieve the allowable error in the meter-in flow rate of each hydraulic actuator 6, 25 to 27 is set as the limit flow rate.

[0111] The actuator speed limit calculation unit 218A calculates the speeds of the hydraulic actuators 6, 25 to 27 corresponding to the final target flow rate Qp_Ft of the hydraulic pumps 31 to 33, which is the calculation result of the pump target flow rate calculation unit 213A, as the speed limit Va_lim of the hydraulic actuators 6, 25 to 27. The calculated speed limit Va_lim of the hydraulic actuators 6, 25 to 27 is output to the actuator target speed calculation unit 211.

[0112] The flow control valve target opening calculation unit 215A calculates the target opening Af_t of each of the flow control valves 51 to 59 based on the operation amount (instruction information) of each of the operation levers 141, 142 of the operation device. For this calculation, for example, a map stored in advance in the storage device 201 is used. The target opening Af_t of each of the flow control valves 51 to 59 as a result of the calculation is output to the flow control valve control command calculation unit 216.

[0113] Next, the control procedure of the hydraulic system by the control device for the construction machine according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is a flowchart showing an example of the control procedure by the control device for the construction machine according to the second embodiment shown in Fig. 9.

[0114] The control procedure of the control device according to the second embodiment shown in FIG. 12 differs from the control procedure of the control device according to the first embodiment (see FIG. 7) in that the processing content of steps S20A and S50A for calculating the pump final target flow rate Qp_Ft and the target openings Af_t of the flow control valves 51 to 59 is different, and the processing content of step S70A for calculating the speed limit Va_lim of the hydraulic actuators 6, 25 to 27 is different. Furthermore, the processing of step S60 in the first embodiment is unnecessary. The processing of the other steps in the second embodiment is the same as the steps in the first embodiment, and therefore a description thereof will be omitted.

[0115] 12, if the control device 200A shown in FIG. 9 determines in step S10 that an operation signal has been input (YES), the control device 200A proceeds to step S20A and step S30. In step S20A, similar to the first embodiment, the control device 200A calculates the target opening Ad_t of each directional control valve 36-46 and calculates the target opening Ac_t of each CB cut valve 61-63. Furthermore, unlike the first embodiment, the control device 200A calculates the target opening Af_t of each flow control valve 51-59 based on the operation amount (instruction information) of the operating devices 141, 142.

[0116] In step S50A, the control device 200A calculates the maximum value of the target flow rates Qa_t of the hydraulic actuators 6, 25 to 27, which are the calculation results of step S40, and the limit flow rate Qp_lim of the set value, as the final target pump flow rate Qp_Ft of the hydraulic pumps 31 to 33. Next, the control device 200A calculates the speed of each hydraulic actuator 6, 25 to 27 corresponding to the final target pump flow rate Qp_Ft of the hydraulic pumps 31 to 33, which is the calculation result of step S50A, as the speed limit Va_lim (step S70A).

[0117] Next, the control device 200A determines whether the target speed Va_t of each hydraulic actuator 6, 25 to 27, which is the calculation result of step S30, is smaller than the speed limit Va_lim of each hydraulic actuator 6, 25 to 27, which is the calculation result of step S70A (Va_t<Va_lim) (step S80).

[0118] If it is determined in step S80 that the target speed Va_t is smaller than the speed limit Va_li (YES), the calculation result of step S30 is discarded, and the target speed Va_t of each hydraulic actuator 6, 25 to 27 is recalculated using the speed limit Va_lim of the hydraulic actuators 6, 25 to 27 that is the calculation result of step S70A (step S90). The recalculation of the target speed Va_t of each hydraulic actuator 6, 25 to 27 is based on the speed limit Va_lim of the hydraulic actuator when the limit flow rate Qp_lim is selected as the pump final target flow rate Qp_Ft, and the target speed Va_lim of each hydraulic actuator that is necessary for executing range limit control is recalculated.

[0119] In step S90, the target speed Va_t of each hydraulic actuator 6, 25 to 27 is recalculated using the speed limit Va_lim of the hydraulic actuators 6, 25 to 27, and the processing of steps S40, S50A, S70A, and S80 is then redone using the recalculated target speed Va_t of each hydraulic actuator 6, 25 to 27. As a result, the final pump target flow rate Qp_Ft of the hydraulic pumps 31 to 33 is recalculated taking into account the speed limit Va_lim of the hydraulic actuators 6, 25 to 27.

[0120] As described above, in the present embodiment, the final target flow rate Qp_Ft of the hydraulic pumps 31 to 33 is set to be equal to or greater than the limit flow rate Qp_lim at which control accuracy can be ensured during range limit control of the working implement 4. Therefore, the accuracy of flow rate control for the hydraulic actuators 25 to 27 can be ensured by the flow rate control of the hydraulic actuators 25 to 27 by the hydraulic pumps 31 to 33.

[0121] If the target speed Va_t of the hydraulic actuators 25 to 27 falls below the speed limit Va_lim, the target speed Va_t of the hydraulic actuators 25 to 27 is recalculated so as to ensure the accuracy of the flow rate control of the hydraulic pumps 31 to 33 while maintaining the movement direction of the bucket 23 according to the operation of the operation devices 141, 142. This ensures the accuracy of the flow rate control by the hydraulic pumps 31 to 33 for the hydraulic actuators 25 to 27, allowing the movement of the bucket 23 to be accurately controlled.

[0122] In the second embodiment described above, if the target value for controlling the hydraulic pumps 31 to 33, which serve as hydraulic devices that adjust the flow rates supplied to the hydraulic actuators 25 to 27, falls below the lower limit value at which the accuracy of flow rate control can be ensured, the target value of the hydraulic pumps 31 to 33 (hydraulic devices) that corresponds to the target speed Va_t of the hydraulic actuators 25 to 27, recalculated based on the speed limit Va_lim of the hydraulic actuators 25 to 27 calculated using this lower limit value, is used as the control target.Therefore, even when the working device 4 is operated by driving the hydraulic actuators 25 to 27 at low speeds during range limit control of the working device 4, it is possible to prevent a decrease in the accuracy of the flow rate control for the hydraulic actuators 25 to 27, and it is possible to accurately control the operation of the working device 4.

[0123] In this embodiment, the hydraulic equipment is hydraulic pumps 31 to 33 that supply pressure oil to the hydraulic actuators 25 to 27, and the target values ​​of the hydraulic equipment are target flow rates of the hydraulic pumps 31 to 33 that are calculated based on the target flow rates of the hydraulic actuators obtained from the calculated target speeds of the hydraulic actuators 25 to 27. The lower limit value is a limit flow rate that is set in advance for the hydraulic pumps 31 to 33 depending on the accuracy of the flow rate control. The speed limits of the hydraulic actuators 25 to 27 in the control device 200A are calculated based on the limit flow rates of the hydraulic pumps 31 to 33.

[0124] According to this configuration, in the operation restriction control of the working implement 4, the operation of the working implement 4 can be accurately controlled by controlling the flow rates of the hydraulic pumps 31 to 33 for the hydraulic actuators 25 to 27.

[0125] [Other Embodiments] The present invention is not limited to the first embodiment described above, and includes various modifications. The above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to an embodiment having all of the described configurations. It is also possible to add, delete, or replace part of the configuration of this embodiment with other configurations.

[0126] For example, in the first and second embodiments described above, an example of a configuration was shown in which the control devices 200, 200A control the openings of the directional control valves 37-42, 44-46 and the flow control valves 51-59 and the flow rates of the hydraulic pumps 31-33 based on instruction information as the operation of the control levers 141, 142 of the operating device that instructs the operation of the revolving unit 3 and the work devices 21, 22, 23. However, the control devices 200, 200A can also be configured to control the openings of the directional control valves 37-42, 44-46 and the flow control valves 51-59 and the flow rates of the hydraulic pumps 31-33 based on instruction information as the operation of a remote control device that remotely instructs the operation of the revolving unit 3 and the work devices 21, 22, 23. In addition, the control devices 200, 200A can also be configured to control the opening of the directional control valves 37-42, 44-46 and the flow control valves 51-59 and the flow rate of the hydraulic pumps 31-33 based on instruction information as operation instructions for the rotating body 3 and the work devices 21, 22, 23 that they themselves generate to automatically control the rotating body 3 and the work devices 21, 22, 23 to perform operations that satisfy specified conditions.

[0127] Furthermore, in the above-described first and second embodiments, an example has been shown in which the flow control valves 51 to 59 are used as control valves that can control the flow rate of pressure oil supplied to the hydraulic actuators 25 to 27 that drive the working device 4. However, it is also possible to use a directional control valve that controls the direction of supply / discharge of pressure oil to / from the hydraulic actuators as a control valve that can control the flow rate of pressure oil supplied to the hydraulic actuators 25 to 27. In this configuration, it is possible to control the flow rate of pressure oil supplied to the hydraulic actuators 25 to 27 by the meter-in opening area of ​​the directional control valve.

[0128] REFERENCE SIGNS LIST 1...hydraulic excavator (construction machinery), 4...working device, 23...bucket (working implement), 25...boom cylinder (hydraulic actuator), 26...arm cylinder (hydraulic actuator), 27...bucket cylinder (hydraulic actuator), 31...first hydraulic pump (hydraulic pump), 32...second hydraulic pump (hydraulic pump), 33...third hydraulic pump (hydraulic pump), 37, 38, 39, 40, 41, 42, 45, 46...directional control valve, 51, 52, 53, 54, 55, 56, 58, 59...flow rate control valve (control valve), 121, 122, 123...pressure sensor (pressure detection device), 124, 125, 126...pressure sensor (pressure detection device), 131, 132, 133, 134, 135...IMU (attitude detection device), 200, 200A...control device

Claims

1. A construction machine comprising: a working device including a working implement; at least one hydraulic actuator for driving the working device; hydraulic equipment capable of adjusting a flow rate of pressurized oil supplied to the hydraulic actuator; a control device for controlling the hydraulic actuator via the hydraulic equipment so as to satisfy a condition that the working implement does not move beyond a target plane set as a work target of the working implement; and a posture detection device for detecting the posture of the working implement, wherein the control device: calculates, based on detection information from the posture detection device and setting information from the target plane, a speed of the hydraulic actuator at which the working implement satisfies the condition as a target speed; calculates a target value of the hydraulic equipment corresponding to the calculated target speed of the hydraulic actuator; if the calculated target value of the hydraulic equipment is smaller than a lower limit value at which an allowable accuracy of flow rate control by the hydraulic equipment can be ensured, calculates the speed of the hydraulic actuator obtained from the lower limit value as a limit speed of the hydraulic actuator; and recalculate the target speed of the hydraulic actuator at which the working implement satisfies the condition based on the calculated limit speed of the hydraulic actuator; a hydraulic actuator for controlling a hydraulic device by setting the target value of the hydraulic device as a control target in accordance with the recalculated target speed of the hydraulic actuator.

2. A construction machine as described in claim 1, wherein the at least one hydraulic actuator that drives the working implement is composed of a plurality of hydraulic actuators, and the calculation of the target speed of the hydraulic actuator in the control device calculates the target speed of each of the plurality of hydraulic actuators based on the detection information of the attitude detection device and the setting information of the target surface, as well as the movement direction of the working implement obtained from instruction information that instructs the operation of the working implement, and the recalculation of the target speed of the hydraulic actuator in the control device calculates, based on the calculated speed limit, the speed of the plurality of hydraulic actuators that satisfies the condition while the working implement maintains the movement direction.

3. A construction machine as claimed in claim 1, characterized in that the hydraulic equipment is a flow control valve capable of controlling the flow rate of pressurised oil supplied to the hydraulic actuator, and further comprising a pressure detection device which detects a pressure difference across the flow control valve, the target value of the hydraulic equipment is a target opening area of ​​the flow control valve calculated based on a target flow rate of the hydraulic actuator obtained from the calculated target speed of the hydraulic actuator and the detection value of the pressure detection device, the lower limit value is a limit opening area which is preset for the flow control valve in accordance with the accuracy of its flow control, and the calculation of the speed limit of the hydraulic actuator in the control device is based on a flow rate calculated using the limit opening area of ​​the flow control valve and the detection value of the pressure detection device.

4. A construction machine as claimed in claim 3, further comprising a directional control valve capable of controlling the flow direction of pressurized oil supplied to the hydraulic actuator and controlling the flow of pressurized oil discharged from the hydraulic actuator, wherein the flow control valve is arranged upstream of the directional control valve, the pressure detection device includes a pressure sensor which detects the meter-in pressure and meter-out pressure of the hydraulic actuator, and the control device controls the meter-out opening of the directional control valve based on thrust information or pressure information of the hydraulic actuator obtained from the detection value of the pressure sensor.

5. A construction machine as described in claim 1, wherein the hydraulic equipment is a hydraulic pump which supplies pressurized oil to the hydraulic actuator, the target value of the hydraulic equipment is a target flow rate of the hydraulic pump calculated based on a target flow rate of the hydraulic actuator obtained from the calculated target speed of the hydraulic actuator, the lower limit value is a limit flow rate which is preset for the hydraulic pump in accordance with the accuracy of its flow control, and the calculation of the speed limit of the hydraulic actuator in the control device is performed based on the limit flow rate of the hydraulic pump.

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