Patent Application
20220186459
The present invention relates to a hydraulic excavator including a machine control function.
Some hydraulic excavators include a machine control (hereinafter referred to as “MC” as required) function for assisting an operator in operating a front implement. One typical example of the MC function is an area limiting control in which a boom cylinder, for example, is forcibly controlled for intervening in an operator's excavating operation, for example, to prevent a claw tip of a bucket from entering an area below an excavation target surface.
With regard to the area limiting control, Patent Document 1 discloses a system for correcting for deceleration a target velocity vector of a work implement in a direction toward an excavation target surface when the work implement approaches the excavation target surface. During the area limiting control, however, since a velocity component at which the work implement moves toward the excavation target surface is reduced as the work implement approaches the excavation target surface, the work implement is unable to perform compaction work.
On the other hand, Patent Document 2 discloses a system in which when it is determined that compacting conditions are satisfied on the basis of operator's operation, a velocity limit for a boom lowering action of a work implement in the vicinity of an excavation target surface is eased up, allowing the work implement to compact the excavation target surface even during the area limiting control.
The MC function is realized by reducing, with a solenoid pressure reducing valve, depending on a situation, a pilot pressure applied from a control lever device to a flow control valve that controls an action of a hydraulic actuator of a work implement such as a boom cylinder or the like. Then, according to the MC function, from the standpoint of preventing the work implement from excavating soil beyond the target excavation surface, the solenoid pressure reducing valve has its opening set to a closed side in a standby mode in order to restrain the work implement from operating abruptly. The solenoid pressure reducing valve is opened when the hydraulic actuator is allowed to operate quickly.
According to the system disclosed in Patent Document 2, when compaction work is determined, the velocity limit for the boom lowering operation is eased up. However, compaction work is not performed by only the boom lowering operation, but performed in combination with arm crowding and arm dumping actions for adjusting a compacting position. Since the arm crowding and arm dumping actions are limited in the vicinity of the surface being excavated, the adjustment operation of the compacting position is delayed, making it impossible to perform the compaction work smoothly.
It is an object of the present invention to provide a hydraulic excavator that is capable of performing work such as compaction work involving arm crowding and arm dumping actions with a good response in the vicinity of an excavation target surface even during a machine control.
In order to achieve the above object, there is provided, according to the present invention, a hydraulic excavator including: a multi-joint work implement including a boom and an arm; a plurality of hydraulic actuators that actuate the work implement, the hydraulic actuators including a boom cylinder for actuating the boom; a plurality of posture sensors that detect a posture of the work implement; a hydraulic pump that discharges a hydraulic fluid actuating the plurality of hydraulic actuators; a control valve unit that controls a flow of the hydraulic fluid supplied from the hydraulic pump to the plurality of hydraulic actuators; a plurality of control lever devices that output a pilot pressure actuating the control valve unit, with use of a discharged pressure from a pilot pump as a source pressure; a solenoid valve unit including a plurality of solenoid pressure reducing valves connected between the plurality of control lever devices and the control valve unit; and a controller configured to calculate velocity limits for the plurality of hydraulic actuators on the basis of signals from the plurality of posture sensors and control openings of the solenoid pressure reducing valves to prevent the work implement from excavating soil beyond a target excavation surface on a basis of the velocity limits, in which the controller is configured to control the openings of the solenoid pressure reducing valves included in the solenoid valve unit and corresponding to arm crowding and arm dumping actions to be larger than an opening based on the velocity limits while a boom raising operation signal is being output from the control lever devices.
According to the present invention, it is possible to perform work such as compaction work involving arm crowding and arm dumping actions with a good response in the vicinity of an excavation target surface even during a machine control.
Embodiments of the present invention will be described hereinbelow with reference to the drawings.
The hydraulic excavator 1, illustrated in
The work implement 1A is made up of a plurality of driven members (a boom 8, an arm 9, and a bucket 10) each angularly movable in a vertical plane, coupled together. The boom 8 has a proximal end angularly movably coupled to a front portion of the swing structure 12 by a boom pin. The arm 9 is angularly movably coupled to a distal end of the boom 8. The bucket 10 is angularly movably coupled to a distal end of the arm 9 by a bucket pin. The boom 8 is actuated by a boom cylinder 5, the arm 9 is actuated by an arm cylinder 6, and the bucket 10 is actuated by a bucket cylinder 7.
Also, an angle sensor R1 is attached to the boom pin. An angle sensor R2 is attached to the arm pin. An angle sensor R3 is attached to a bucket link 13. A vehicle body tilt angle sensor (e.g., an IMU) R4 is attached to the swing structure 12. The angle sensors R1, R2, and R3 measure respective angles α,β, and γ (
Note that, according to the present embodiment, the reference point of the work implement 1A will be described as being set to a bucket claw tip, by way of example. However, the reference point can be set to various points appropriately. For example, the reference point may be set to a point on a rear side surface (an outer surface) of the bucket 10 or a point on the bucket link 13 or a point on the bucket 10 that is spaced the shortest distance from a target excavation surface St (in other words, the reference point may be varied depending on a situation).
The swing structure 12 has an engine 18 as a prime mover and also a hydraulic pump 2 and a pilot pump 48 mounted thereon. The engine 18 actuates the hydraulic pump 2 and the pilot pump 48. The hydraulic pump 2 is of variable displacement type whose displacement is controlled by a regulator 2a, and discharges a hydraulic fluid for actuating a plurality of hydraulic actuators (including the boom cylinder 5, the arm cylinder 6, the bucket cylinder 7 and the like). The pilot pump 48 is of fixed displacement type. In the example illustrated in
A pump line 48a as a discharge conduit from the pilot pump 48 extends through a lock valve 39 and branches off into a plurality of lines that are connected to the control lever devices A1 through A6 and a solenoid valve unit 160 for machine control. The lock valve 39 according to the present embodiment is a solenoid selector valve having a solenoid electrically connected to a positional sensor of a gate lock lever (not shown) disposed in the operator's cabin 16 of the swing structure 12. The positional sensor detects the position of the gate lock lever and inputs a signal representing the detected position of the gate lock lever to the lock valve 39. When the gate lock lever is in a lock position, the lock valve 39 is closed, cutting off the pump line 48a. When the gate lock lever is in an unlock position, the lock valve 39 is opened, opening the pump line 48a. When the pump line 48a is in an interruption state, the control lever devices A1 through A6 are disabled, prohibiting the hydraulic excavator 1 from swinging, excavating, and making other operations.
Each of the control lever devices A1 through A6 includes a pair of pressure reducing valves of the pilot-operated type. These control lever devices A1 through A6 generate and emit pilot pressures for actuating a control valve unit 15 depending on operation amounts and directions of the control levers B1 through B4, using a discharged pressure from the pilot pump 48 as a source pressure. The control valve unit 15 includes flow control valves D1 through D6, and controls flows of the hydraulic fluid supplied from the hydraulic pump 2 to the boom cylinder 5, the arm cylinder 6, the bucket cylinder 7, the track motors 3a and 3b, and the swing motor 4. The flow control valve D1 is actuated by pilot pressures applied from the control lever device A1 through pilot lines C1 and C2 to pressure bearing chambers E1 and E2 to control the direction and flow rate of the hydraulic fluid supplied from the hydraulic pump 2 to actuate the boom cylinder 5. The flow control valve D2 is actuated by pilot pressures applied from the control lever device A2 through pilot lines C3 and C4 to pressure bearing chambers E3 and E4 to actuate the arm cylinder 6. The flow control valve D3 is actuated by pilot pressures applied from the control lever device A3 through pilot lines C5 and C6 to pressure bearing chambers E5 and E6 to actuate the bucket cylinder 7. Similarly, the flow control valves D4 through D6 are actuated by pilot pressures applied from the control lever devices A4 through A6 through pilot lines C7 through C12 to pressure bearing chambers E7 through El2 to actuate the corresponding hydraulic actuators.
The solenoid pressure reducing valve V1′ has a primary port connected through the pump line 48a to the pilot pump 48, and reduces the discharged pressure from the pilot pump 48 and emits the reduced pressure as a pilot pressure (second command signal) for boom raising. The shuttle valve SV1 has primary ports connected respectively to the pilot line C1 for boom raising from the control lever device A1 and a secondary port of the solenoid pressure reducing valve V1′, and has a secondary port connected to the pressure bearing chamber E1 of the flow control valve D1. For boom raising action, a higher one of the first command signal (boom raising operation signal) from the pilot line C1 and the second command signal from the solenoid pressure reducing valve V1′ is selected by the shuttle valve SV1 and introduced into the pressure bearing chamber E1 of the flow control valve D1.
The solenoid pressure reducing valve V2 is disposed to the pilot line C2 for boom lowering action from the control lever device A1. For boom lowering action, a pilot pressure from the pilot line C1 that is reduced by the solenoid pressure reducing valve V2 as required is introduced into the pressure bearing chamber E2 of the flow control valve D1.
The solenoid pressure reducing valve V3 is disposed to the pilot line C3 for arm crowding from the control lever device A2. For arm crowding, a pilot pressure from the pilot line C3 that is reduced by the solenoid pressure reducing valve V3 as required is introduced into the pressure bearing chamber E3 of the flow control valve D2.
The solenoid pressure reducing valve V4 is disposed to the pilot line C4 for arm dumping from the control lever device A2. For arm dumping action, a pilot pressure from the pilot line C4 that is reduced by the solenoid pressure reducing valve V4 as required is introduced into the pressure bearing chamber E4 of the flow control valve D2.
The solenoid pressure reducing valve V5 is disposed to the pilot line C5 for bucket crowding from the control lever device A3. The solenoid pressure reducing valve V5′ has a primary port connected through the pump line 48a to the pilot line 48, and reduces the discharged pressure from the pilot pump 48 and emits the reduced pressure as a pilot pressure (second command signal) for bucket crowding. The shuttle valve SV5 has primary ports connected respectively to the pilot line C5 and a secondary port of the solenoid pressure reducing valve V5′, and has a secondary port connected to the pressure bearing chamber E5 of the flow control valve D3. For bucket crowding action, a higher one of the pilot pressure from the pilot line C5 and the pilot pressure from the solenoid pressure reducing valve V5′ is selected by the shuttle valve SV5 and introduced into the pressure bearing chamber E5 of the flow control valve D3.
The solenoid pressure reducing valve V6 is disposed to the pilot line C6 for bucket dumping from the control lever device A3. The solenoid pressure reducing valve V6′ has a primary port connected through the pump line 48a to the pilot line 48, and reduces the discharged pressure from the pilot pump 48 and emits the reduced pressure as a pilot pressure (second command signal) for bucket dumping. The shuttle valve SV6 has primary ports connected respectively to the pilot line C6 and a secondary port of the solenoid pressure reducing valve V6′, and has a secondary port connected to the pressure bearing chamber E6 of the flow control valve D3. For an bucket dumping action, a higher one of the pilot pressure from the pilot line C6 and the pilot pressure from the solenoid pressure reducing valve V6′ is selected by the shuttle valve SV6 and introduced into the pressure bearing chamber E6 of the flow control valve D3.
The solenoid pressure reducing valves V2 through V6 are of normally open type in which their openings are maximum (an open state), when their solenoid is de-energized. In proportion to an increase in command signals (electric signals) from the controller 40, their openings are reduced to a minimum opening (opening 0 according to the present embodiment). On the other hand, the solenoid pressure reducing valves V1′, V5′, and V6′ are of normally closed type in which their openings are minimum (opening 0 according to the present embodiment) when their solenoid is de-energized. In proportion to an increase in command signals (electric signals) from the controller 40, their openings are increased to a maximum opening. When the solenoid pressure reducing valves V2 through V6 are actuated by the command signals from the controller 40, they generate pilot pressures (second command signals) by reducing and correcting the pilot pressures (first command signals) generated by the control lever devices A1 through A3. On the other hand, when the solenoid pressure reducing valves V1′, V5′, and V6′ are actuated by the command signals from the controller 40, they generate pilot pressures (second command signals) for boom raising, bucket crowding, and bucket dumping, regardless of operation of the control lever devices A1 and A3. The second command signals represent pilot pressures controlled by the controller 40 under MC. The controller 40 thus operates the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′ to intervene in operator's operation under certain conditions to correct an action of the work implement 1A in order for the work implement 1A not to excavate soil beyond an excavation target surface St (
Note that the hydraulic excavator 1 includes pressure sensors P1 through P6. The pressure sensors P1 and P2 are disposed to the pilot lines C1 and C2, respectively, that interconnect the control lever device A1 and the flow control valve D1 for the boom. The pressures in the pilot lines C1 and C2, i.e., the pilot pressures (first command signals) upstream of the solenoid pressure reducing valves are detected by the pressure sensors P1 and P2, respectively, as operation amounts of the boom brought about by the control lever B1. The pressure sensors P3 and P4 are disposed to the pilot lines C3 and C4, respectively, that interconnect the control lever device A2 and the flow control valve D2 for the arm. The pressures in the pilot lines C3 and C4, i.e., the pilot pressures (first command signals) upstream of the solenoid pressure reducing valves V3 and V4 are detected by the pressure sensors P3 and P4, respectively, as operation amounts of the arm brought about by the control lever B2. The pressure sensors P5 and P6 are disposed to the pilot lines C5 and C6, respectively, that interconnect the control lever device A3 and the flow control valve D3 for the bucket. The pressures in the pilot lines C5 and C6, i.e., the pilot pressures (first command signals) upstream of the solenoid pressure reducing valves V5 and V6 are detected by the pressure sensors P5 and P6, respectively, as operation amounts of the bucket brought about by the control lever B1. Detected signals from the pressure sensors P1 through P6 are input to the controller 40. Lines interconnecting the pressure sensors P1 through P6 and the controller 40 are omitted from illustration.
The posture of the work implement 1A can be defined by a local coordinate system for excavators illustrated in
At this time, the position (Xbk and Zbk) of the bucket claw tip in the local coordinate system is expressed by the following equations (1) and (2):
Xbk=L1 cos(α)+L2 cos(α+β)+L3 cos(α+β+γ) (1)
Zbk=L1 sin(α)+L2 sin(α+β)+L3 sin(α+β+γ) (2)
where L1 represents a length from the proximal portion of the boom 8 to the portion thereof that is coupled to the arm 9, L2 a length from the portion of the boom 8 that is coupled to the arm 9 to the portion of the arm 9 that is coupled to the bucket 10, and L3 a length from the portion of the arm 9 that is coupled to the bucket 10 to a tip end of the bucket 10.
The controller 40 has an MC function to intervene in operator's operation under certain conditions to limit action of the work implement 1A when at least one of the control lever devices A1 through A3 is operated. MC is performed when the controller 40 controls the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′ depending on the bucket claw tip position and the operated situation. The MC function that can be installed in the controller 40 includes “area limiting control” that is carried out when the operator operates the arm with the control lever device A2 and “stop control” and “compaction control” that are carried out when the operator lowers the boom without operating the arm.
The area limiting control is also referred to as “leveling control.” While the area limiting control is functioning, at least one of the boom cylinder 5, the arm cylinder 6, and the bucket cylinder 7 is controlled such that the work implement 1A will not excavate an area below the target excavation surface St, and the arm is operated to move the bucket claw tip along the target excavation surface St. Specifically, while the arm is moving due to arm operation, fine movement for raising the boom or lowering the boom is commanded in order to make zero the velocity vector of the bucket claw tip in a direction perpendicular to the target excavation surface St. This is to correct the trajectory of the bucket claw tip brought about by an arm action that is a rotary motion into a linear trajectory along the target excavation surface St.
The stop control is a control for stopping a boom lowering action such that the bucket claw tip will not enter an area below the target excavation surface St, and decelerates a boom lowering action as the bucket claw tip approaches the target excavation surface St while the boom lowering is operated.
The compaction control is a control for allowing compaction work. Compaction work refers to a work for compacting a ground surface by pressing a rear side surface of the bucket 10 forcefully against the ground surface. According to the MC, however, since the velocity at which the bucket claw tip approaches the target excavation surface St is basically reduced in the vicinity of the target excavation surface St, even when the operator operates the boom to lower the boom, intending to compact the target excavation surface St that has been shaped, the bucket 10 cannot be pressed forcefully against the target excavation surface St. While the compaction control is functioning, the deceleration of a boom lowering action is suppressed even if the distance between the target excavation surface St and the bucket claw tip is small (as described later).
The controller 40 illustrated in
The input interface 41 is supplied with signals input from a posture sensor R, a target surface setting device Ts, the GNSS antennas G1 and G2, an operation sensor P, and a mode switch SW, and converts the supplied signals into digital signals as required for calculations performed by the CPU 42. Note that the posture sensor R includes a plurality of sensors installed for detecting the posture of the work implement LA, the sensors specifically including the angle sensors R1 through R3 and the vehicle body tilt angle sensor R4. The operation sensor P includes the pressure sensors P1 through P6. The target surface setting device Ts is an interface for entering information regarding the target excavation surface St (the information including positional information and tilt angle information of the target excavation surface). The target surface setting device Ts is connected to an external terminal (not shown) that stores therein three-dimensional data on target excavation surfaces defined in a global coordinate system (absolute coordinate system), and is supplied with three-dimensional data on a target excavation surface input from the external terminal. However, a target excavation surface can also manually be input by the operator to the controller 40 via the target surface setting device Ts. The mode switch SW is an input device for setting a work mode.
The ROM 43 stores therein control programs for performing the MC function including processing sequences to be described subsequently with reference to
The CPU 42 carries out predetermined calculating processing on the basis of signals read from the input interface 41, the ROM 43, and the RAM 44 according to the control programs stored in the ROM 43.
The output interface 45 generates signals to be output on the basis of calculated results from the CPU 42, and outputs the generated signals to the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′ and the display device DS, thereby actuating the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′ and the display device DS. The display device DS is a liquid crystal monitor of touch panel type and is installed in the operator's cabin 16. As illustrated in
As illustrated in
(1) Operation amount calculating section
The operation amount calculating section 42A calculates operation amounts of the control lever devices A1, A2, and A3 (the control levers B1 and B2) on the basis of detected values from the operation sensor P (the pressure sensors P1 through P6). The operation amount calculating section 42A calculates an operation amount for boom raising from the detected value from the pressure sensor P1, calculates an operation amount for boom lowering from the detected value from the pressure sensor P2, calculates an operation amount for arm crowding (arm pulling) from the detected value from the pressure sensor P3, and calculates an operation amount for arm dumping (arm pushing) from the detected value from the pressure sensor P4. The operation amount calculating section 42A calculates an operation amount for bucket crowding from the detected value from the pressure sensor P5, and calculates an operation amount for bucket dumping from the detected value from the pressure sensor P6. The operation amounts converted from the detected values from the pressure sensors P1 through P6 by the operation amount calculating section 42A are output to the velocity limit calculating section 42D.
Note that the calculation of operation amounts on the basis of the detected values from the pressure sensors P1 through P6 is by way of example only. Operation amounts of the control levers may be detected by positional sensors (for example, rotary encoders) that detect angular displacements of the control levers of the control lever devices A1 through A3, for example.
(2) Posture Calculating Section
The posture calculating section 42B calculates a posture of the work implement 1A and a position of the claw tip of the bucket 10 in the local coordinate system on the basis of detected signals from the posture sensor R. The position (Xbk and Zbk) of the claw tip of the bucket 10 can be calculated according to the equations (1) and (2) as described above. When a posture of the work implement 1A and a position of the claw tip of the bucket 10 in the global coordinate system are required, the posture calculating section 42B calculates a position and posture in the global coordinate system of the swing structure 12 from the signals from the GNSS antennas G1 and G2, and converts the local coordinate system into the global coordinate system.
(3) Target Surface Calculating Section
The target surface calculating section 42C calculates positional information of a target excavation surface St on the basis of information entered via the target surface setting device Ts, and the calculated positional information of the target excavation surface St is recorded in the RAM 44. According to the present embodiment, information of a cross section (a two-dimensional target excavation surface illustrated in
Note that, in the example illustrated in
(4) Velocity Limit Calculating Section
The velocity limit calculating section 42D calculates respective velocity limits (limit values for elongation velocities) for the boom cylinder 5, the arm cylinder 6, and the bucket cylinder 7 at a time of MC (at a time of area limiting control) on the basis of the signals from the posture sensor R so that the work implement 1A will not excavate soil beyond the target excavation surface St. According to the present embodiment, first, respective primary target velocities for the boom cylinder 5, the arm cylinder 6, and the bucket cylinder 7 are calculated on the basis of the operation amounts of the control lever devices A1 through A3 that are entered from the operation amount calculating section 42A. Then, a target velocity vector Vc (
At this time, the directional conversion control may be carried out in a combination of boom raising or boom lowering and arm crowding or in a combination of boom raising or boom lowering and arm dumping. Even in either case, when the target velocity vector Vc includes a downward component (Vcy<0) toward the target excavation surface St, the velocity limit calculating section 42D calculates a velocity limit for the boom cylinder 5 in a boom raising direction to cancel out the downward component. Conversely, when the target velocity vector Vc includes an upward component (Vcy>0) away from the target excavation surface St, the velocity limit calculating section 42D calculates a velocity limit for the boom cylinder 5 in a boom lowering direction to cancel out the upward component. Furthermore, taking into account response delays of the solenoid pressure reducing valves V2 and V1′ and the like. for the boom action, a ratio at which a velocity limit for arm crowding increases is limited and output immediately after an arm crowding operation. Similarly, a ratio at which a velocity limit for arm dumping increases is limited and output immediately after an arm dumping operation.
Note that, when no area limiting control is carried out, the velocity limit calculating section 42D calculates and outputs velocity limits (primary target velocities) for the hydraulic cylinders depending on the operation of the control lever devices A1 through A3 as they are as velocity limits.
The velocity limits calculated by the velocity limit calculating section 42D are output to the limiting pilot pressure calculating section 42a.
(5) Limiting Pilot Pressure Calculating Section
The limiting pilot pressure calculating section 42a calculates a limiting pilot pressure Pr1 for the flow control valves D1, D2, and D3 corresponding respectively to the boom cylinder 5, the arm cylinder 6, and the bucket cylinder 7 on the basis of the velocity limits calculated by the velocity limit calculating section 42D. The limiting pilot pressure Pr1 calculated by the limiting pilot pressure calculating section 42a is output to the intervention determining section 42b.
(6) Limiting Pilot Pressure Intervention Determining Section
The intervention determining section 42b determines a final limiting pilot pressure Pr2 on the basis of the limiting pilot pressure Pr1 calculated by the limiting pilot pressure calculating section 42a, with a change added thereto under certain conditions as required. Specifically, in a situation for suppressing limitation on motion velocities under MC for boom lowering, arm dumping, and arm crowding, the limiting pilot pressure Pr2 for the pressure bearing chambers E2 through E4 of the flow control valves D1 and D2 that have been calculated by the limiting pilot pressure calculating section 42a is changed in an increasing direction. Because of the function of the intervention determining section 42b, even in a situation where the actuator speeds are limited under MC, the openings of the solenoid pressure reducing valves V2 through V4 increase from the original openings (openings based on the velocity limits calculated by the velocity limit calculating section 42D) under MD under a certain condition. In this case, limitation under MC on the actions of boom lowering, arm dumping, and arm crowding is eased up. The limiting pilot pressure is changed by the intervention determining section 42b on the basis of the target surface distance H1, the situation of a boom raising operation, and the limiting pilot pressures corresponding respectively to the actions of arm crowding, arm dumping, and boom lowering. When there is no need to change the limiting pilot pressure, the limiting pilot pressure Pr2 determined by the intervention determining section 42b becomes the limiting pilot pressure Pr1 determined by the limiting pilot pressure calculating section 42a (the pilot pressure based on the velocity limits calculated by the velocity limit calculating section 42D). A processing sequence of the intervention determining section 42b will be described later with reference to
(7) Valve Command Calculating Section
The valve command calculating section 42c calculates an electric signal based on the limiting pilot pressure Pr2 determined by the intervention determining section 42b, and outputs the determined electric signal to the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′. The electric signal output from the valve command calculating section 42c energizes the solenoids of the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′, actuating the solenoid pressure reducing valves V2 through V6, V1′, V5′, and V6′, so that the pilot pressure acting on the flow control valves D1 through D3 is limited by the limiting pilot pressure Pr2, depending on a situation. When the operator operates the control lever device A2, intending to excavate soil horizontally with an arm crowding action, for example, the solenoid pressure reducing valves V1′ and V3′ are controlled depending on a situation such that the bucket claw tip will not enter an area below the target excavation surface St. In this case, a decelerating action of arm crowding and a boom raising action are automatically combined with an arm crowding action depending on operator's operation, performing a horizontal excavating operation only with an arm crowding operation while being assisted by the controller 40. On the other hand, while a boom raising operation signal is being output from the control lever device A1, the openings of the solenoid pressure reducing valves V2 through V4 are determined to be larger than an opening based on the velocity limits by the intervention determining section 42b determining to intervene in a target pilot pressure, as described later with reference to
When the processing sequence illustrated in
If H1≥Hth, the intervention determining section 42b determines the limiting pilot pressure Pr2 for the pressure bearing chambers E2 through E4 of the flow control valves D1 and D2 to be the maximum pressure Pmax unconditionally in order to maximize the openings of the solenoid pressure reducing valves V2 through V4 (step S302).
If H1<Hth, then the intervention determining section 42b determines whether a boom raising operation has been made on the basis of the detected signal (pressure) P0 from the pressure sensor P1 (step S303). The intervention determining section 42b here determines whether a boom raising operation has been made by checking if P0≥Pth or not. Pth refers to a preset threshold value stored in the ROM 43 with respect to the detected signal P0 from the pressure sensor P1, and represents a pilot pressure with which the boom 8 starts to be raised. If P0 Pth, then the intervention determining section 42b determines that a boom raising operation has been made, and the sequence goes to step S302. If P0<Pth, then the intervention determining section 42b determines that no boom raising operation has been made, and the sequence goes to step S304. As a result, during the boom raising operation, the solenoid pressure reducing valves V2 through V4 are unconditionally in a standby state with maximum openings, and the MC is canceled irrespective of the target surface distance H1 with respect to arm crowding, arm dumping, and boom lowering operations. Therefore, when an arm crowding operation or an arm dumping operation, for example, is made at the same time as the boom raising operation, the arm 9 can be moved in a crowding direction or a dumping direction at a velocity depending on the operation without being limited by the MC function.
On the other hand, when the bucket claw tip is close to the target excavation surface St and no boom raising operation has been made, the intervention determining section 42b determines whether a non-operation continuation time period Tbm [s] for boom raising is shorter than Tth [s] (step S304). Tth refers to a predetermined time period preset as a threshold value preset with respect to the non-operation continuation time period Tbm and stored in the ROM 43. The intervention determining section 42b here determines whether a time period (=Tbm) that has elapsed from a time period Tbm=0 when the detected signal P0 from the pressure sensor P1 changes from Pth or higher to a value lower than Pth is shorter than Tth. In the intervention determining section 42b, if Tbm<Tth, then the sequence goes to S305, and if Tbm Tth, then the sequence goes to S306.
Until the boom raising operation stops and the predetermined time period Tth is reached (Tbm<Tth), the intervention determining section 42b calculates a transition pressure Ps depending on the non-operation continuation time period Tbm with respect to arm crowding, arm dumping, and boom lowering. Then, the transition pressure Ps is determined as the limiting pilot pressure Pr2 with respect to arm crowding, arm dumping, and boom lowering (step S305). As described later in detail, the transition pressure Ps that is calculated here is a value for returning (for example, monotonously reducing) the openings of the solenoid pressure reducing valves V2 through V4 from the maximum opening (the opening with the MC function canceled) to the opening depending on the limiting pilot pressure Pr1 (the opening with the MC function activated) over the predetermined time period Tth. During a period in which the transition pressure Ps is set as the limiting pilot pressure, the MC function is semi-canceled (MC-based limitation becomes stronger as time elapses) with respect to arm crowding, arm dumping, and boom lowering.
When the non-operation continuation time period Tbm has reached the predetermined time period Tth, the intervention determining section 42b determines whether the limiting pilot pressure Pr1 calculated by the limiting pilot pressure calculating section 42a with respect to arm crowding, arm dumping, and boom lowering is lower than a threshold value Pth2 (step S306). Pth2 refers to a preset threshold value preset for the limiting pilot pressure Pr1 calculated by the limiting pilot pressure calculating section 42a with respect to each of actions of arm crowding, arm dumping, and boom lowering, and represents a pressure at which each of operations of arm crowding, arm dumping, and boom lowering starts, for example. Since the limiting pilot pressure Pr1 can be different for each of actions of arm crowding, arm dumping, and boom lowering, the determined result in step S306 can also be different for each of actions of arm crowding, arm dumping, and boom lowering. The flowchart illustrated in
If the limiting pilot pressure is lower than Pth2, then the intervention determining section 42b determines a minimum pressure Pmin to be the limiting pilot pressure Pr2 (step S307). If the limiting pilot pressure Pr1 is equal to or higher than Pth2, then the intervention determining section 42b determines the limiting pilot pressure Pr1 to be the limiting pilot pressure Pr2 (step S308). MC functions normally in the branch from step S306 to step S308.
When the limiting pilot pressure Pr2 is determined in steps S302, S305, S307, and S309, the intervention determining section 42b outputs the determined limiting pilot pressure Pr2 to the valve command calculating section 42c, whereupon the sequence goes back to step S301 (step S309).
For calculating a transition pressure, the boom raising pilot pressure calculated by the operation amount calculating section 42A is input (S1), and a time (the non-operation continuation time period Tbm) that has elapsed from the time when the boom raising pilot pressure has changed from Pth to a value lower than Pth is calculated (S2). The non-operation continuation time period Tbm is reset to zero each time the boom raising pilot pressure becomes equal to or higher than Pth. The calculated non-operation continuation time period Tbm is input to a pressure ratio table, and a pressure ratio δ (
The present embodiment is characterized in the control of the solenoid pressure reducing valves V2 through V4 with respect to boom lowering, arm crowding, and arm dumping carried out by the solenoid valve unit 160. Action of the solenoid valve unit 160 under certain conditions will be described hereinbelow.
(1) When the bucket claw tip is sufficiently spaced from the target excavation surface St
When the target surface distance H1 calculated by the posture calculating section 42B is equal to or larger than Hth, there is no danger of the work implement 1A interfering with the target excavation surface St, and it is not necessary to intervene in operator's operation to perform deceleration control over boom lowering, arm crowding, and arm dumping. Therefore, irrespectively of the degree of operation, the limiting pilot pressure Pr2 for arm crowding, arm dumping, and boom lowering is set to the maximum pressure Pmax, controlling the solenoid pressure reducing valves V2 through V4 to operate in an opening direction (to be opened according to the present embodiment). Pilot pressures generated by the control lever devices A1 and A2 depending on operator's operation thus act on the pressure bearing chambers E2 through E4 of the flow control valves D2 and D3, so that the boom and the arm are actuated at velocities depending on operator's operation.
(2) When the bucket claw tip is close to the target excavation surface St
Even in a situation where the target surface distance H1 is smaller than Hth, during the boom raising operation, the limiting pilot pressure Pr2 is set to the maximum pressure Pmax irrespectively of the degree of operation with respect to arm crowding, arm dumping, and boom lowering, opening the solenoid pressure reducing valves V2 through V4. According to the present embodiment, the boom raising operation triggers automatic cancelation of MC with respect to arm crowding, arm dumping, and boom lowering, irrespectively of the target surface distance H1 even though the mode switch SW (
Also, according to the present embodiment, when the boom raising operation has stopped, if the target surface distance H1 is smaller than Hth, then the actions of the solenoid pressure reducing valves V2 through V4 do not return immediately to an action under MC. For the predetermined time period Tth from the stopping of the boom raising operation, the limiting pilot pressure Pr2 is set to the transition pressure Ps, irrespectively of the degree of operation with respect to each of actions of arm crowding, arm dumping, and boom lowering. Thus, with respect to the solenoid pressure reducing valves V2 through V4, MC is semi-canceled, making the effect of MC-based action limitation stronger as time elapses from the state in which the boom 8 and the arm 9 are actuated depending on operator's operation. When the predetermined time period Tth elapses without a boom raising operation, the actions of the solenoid pressure reducing valves V2 through V4 return to a normal action under MC.
(1) According to the present embodiment, while a boom raising operation is being made through the control lever device A1, the openings of the solenoid pressure reducing valves V2 and V3 corresponding to arm crowding and arm dumping actions are made larger than an opening based on the velocity limit (a maximum opening according to the present embodiment). Thus, it is possible to intervene in MC and make smooth compaction work and the like including arm crowding and arm dumping actions of the work implement 1A with good response in the vicinity of the target excavation surface St.
In a situation where MC-based assistance is required, mainly an arm operation is made, and a boom raising operation is not generally made. Paying attention to this point, according to the present embodiment, the boom raising operation triggers automatic cancelation of MC with respect to a particular solenoid pressure reducing valve, irrespectively of the target surface distance H1, even though the mode switch SW is not operated, for example. According to the present embodiment, compaction work and the like with no leveling (MC) intended is assumed, and the solenoid pressure reducing valves V2 through V4 strongly related to such work are opened. In this case, when positional alignment is performed by the arm operation after the target excavation surface St and the bucket 10 have been distanced from each other by the boom raising operation in the vicinity of the target excavation surface St, the arm 9 is actuated at a velocity depending on the operation for increased work efficiency even under MC, making the operator less mentally fatigued. The same advantage is achieved also when the bucket 10 is positionally aligned by composite the operations for boom raising and arm crowding (or dumping).
(2) According to the present embodiment, after the boom raising operation has stopped, the openings of the solenoid pressure reducing valves V2 through V4 are monotonously reduced, and returned to an opening based on the limiting pilot pressure Pr1 in the predetermined time period Tth from the stopping of the boom raising operation. MC-based limitation on a boom lowering action after boom raising upon compaction work, for example, is thus suppressed as well, resulting in great advantages of increased work efficiency and reduced operator's mental fatigue.
Furthermore, since the longer the predetermined time period Tth is, the longer the time in which the openings of the solenoid pressure reducing valves V2 through V4 are larger than values under MC is, a long period of time can be secured for improving the responses of arm crowding, arm dumping, and boom lowering after the boom raising operation. Conversely, the shorter the predetermined time period Tth is, the more effective the MC-based original limitation is on the actions of arm crowding, arm dumping, and boom lowering early after the boom raising operation, thereby restraining the work implement from excavating soil beyond the target excavation surface St. The response of the work implement 1A and the protectability of the target excavation surface St can flexibly be adjusted by adjusting the predetermined time period Tth.
The present embodiment is different from the first embodiment with respect to the procedure performed by the intervention determining section 42b for determining a limiting pilot pressure Pr2 for arm crowding, arm dumping, and boom lowering, and specifically with respect to the omission of a procedure for calculating a transition pressure (steps S304 and S305 in
The present embodiment also achieves the basic advantage (1) described in the first embodiment, and is more effective than the first embodiment to reduce the possibility that the work implement may excavate soil beyond the target excavation surface St after the boom raising operation.
For correcting a velocity limit, the boom raising pilot pressure calculated by the operation amount calculating section 42A is input (S11), and a time (the non-operation continuation time period Tbm) that has elapsed from the time when the boom raising pressure has changed from Pth to a value lower than Pth is calculated (S12). The non-operation continuation time period Tbm is reset to zero each time the boom raising pilot pressure becomes equal to or higher than Pth. The calculated non-operation continuation time period Tbm is input to a deceleration ratio table, and a deceleration ratio ε (
At the same time, a velocity limit increasing ratio (=default value>velocity limit increasing ratio to be corrected) after a boom raising operation with respect to arm crowding is input from the ROM 43, for example, (S16), and is multiplied by a ratio (1-ε) (S17). The value of the velocity limit increasing ratio after the boom raising operation that is multiplied by (1-ε) and the value of the velocity limit increasing ratio to be corrected that is multiplied by ε are added to each other, thereby calculating a corrected increasing ratio (S18).
With respect to a velocity limit calculated for arm crowding (S19), the velocity limit to be corrected for arm crowding only immediately after an arm crowding operation (e.g., for the predetermined time period ΔT′ after the stopping of the boom raising operation) is corrected in an increasing direction with the corrected increasing ratio described above (S20). As described above, for a certain period of time after the boom raising operation, the shorter the elapsed time is, the more the velocity limit is corrected to increase because the velocity limit increasing ratio after the boom raising operation that is larger than the velocity limit to be corrected has a strong effect. On the other hand, except immediately after the arm crowding operation (e.g., other than the predetermined time period ΔT′ after the stopping of the boom raising operation) the velocity limit for arm crowding is not corrected. The velocity limit that is thus corrected to increase as required by the velocity limit correcting section 42Da in the velocity limit calculating section 42D is output to the limiting pilot pressure calculating section 42a (S21), and converted into a limiting pilot pressure Pr1 by the limiting pilot pressure calculating section 42a.
As illustrated in
According to the first and second embodiments, arm crowding, arm dumping, and boom lowering are illustrated by way of example as targets for switching control of the limiting pilot pressure Pr2. However, if only arm crowding and arm dumping are targets for improving response delays, then boom lowering may be dropped from the targets for switching control of the limiting pilot pressure Pr2. Conversely, if response delays with respect to bucket dumping and bucket crowding need to be improved, they can also be included as targets. Also with respect to bucket crowding and bucket dumping, a limiting pilot pressure may be calculated, and the degree to which solenoid pressure reducing valves are actuated may be controlled in the same manner as with arm crowding and the like. In this case, the parameters δ, ε, Tth, Pth, and Hth may be shared by or may be set to individual values for arm crowding, arm dumping, boom lowering, bucket crowding, and bucket dumping. Note that, though the solenoid pressure reducing valve V1′ for forced boom raising has not been described in particular, it can be controlled in the same manner as with the solenoid pressure reducing valve V3 and the like. The solenoid of the solenoid pressure reducing valve V1′ can be de-energized (opening 0) when MC is canceled or semi-canceled (e.g., before Tth in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-120376 | Jun 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/024023 | 6/18/2020 | WO | 00 |
