Patent Grant
9284714
The present invention relates to a hydraulic excavator.
As to conventional hydraulic excavators, Japanese Patent Laying-Open No. 7-207697 (PTD 1) discloses such a configuration that an electromagnetic switching valve including an oil passage position with a throttle is provided in a conduit connected to a boom-lowering pilot port of a pilot switching valve for a boom. PTD 1 also discloses such a configuration that a pressure sensor is provided on the boom-lowering pilot port side, and a pressure signal detected by the pressure sensor is inputted to a controller.
PTD 1: Japanese Patent Laying-Open No. 7-207697
In recent years, in work vehicles, there has been known a construction technique of obtaining design surface information from the outside, detecting a position of a work implement and automatically controlling the work implement based on the detected position of the work implement.
In the case of aligning a cutting edge of a bucket with a design surface in a land leveling work with a hydraulic excavator, control for automatically stopping the operation of the work implement at a position where the cutting edge comes into contact with the design surface is executed in order to avoid the cutting edge of the bucket from cutting into the design surface. For precise alignment of the cutting edge of the bucket, it is preferable that an operator operating the hydraulic excavator continues to operate a control lever toward the boom-lowering side until the work implement stops automatically.
When the operator continues to operate the control lever toward the boom-lowering side as described above, a vehicle body shakes after the work implement stops automatically, and at the moment when the cutting edge moves upwardly away from the design surface, boom-lowering is executed. As a result, the cutting edge may invade the design surface.
The present invention has been made in view of the aforementioned problem and an object thereof is to provide a technique that can suppress invasion of the design surface by the work implement.
A hydraulic excavator according to the present invention includes: a boom; a pilot switching valve for the boom; a boom-lowering pilot conduit; a boom-lowering proportional solenoid valve; a control lever; a first pressure sensor; and a controller. The pilot switching valve for the boom has a boom-lowering pilot port and controls operation of the boom. The boom-lowering pilot conduit is connected to the boom-lowering pilot port. The boom-lowering proportional solenoid valve is provided in the boom-lowering pilot conduit. The control lever is operated by an operator. The first pressure sensor detects a pressure generated in the boom-lowering pilot conduit between the control lever and the boom-lowering proportional solenoid valve. The controller controls an opening degree of the boom-lowering proportional solenoid valve based on the pressure detected by the first pressure sensor. The controller gently increases, from zero, a current value outputted to the boom-lowering proportional solenoid valve.
According to the hydraulic excavator of the present invention, by decreasing the response speed of the boom-lowering operation to the operator's operation, it is possible to suppress execution of boom-lowering again when the cutting edge temporarily moves upwardly away from the design surface due to shake of the vehicle body. Therefore, it is possible to prevent a problem that the cutting edge is located lower than the design surface and the design surface is invaded after the shake of the vehicle body stops.
In the hydraulic excavator, an amount of increase in current per unit time when the controller outputs, to the boom-lowering proportional solenoid valve, an instruction signal for instructing an increase in opening degree is smaller than an amount of decrease in current per unit time when the controller outputs, to the boom-lowering proportional solenoid valve, an instruction signal for instructing a decrease in opening degree. Thus, the boom-lowering operation can be immediately stopped when the boom-lowering operation becomes unnecessary.
In the hydraulic excavator, the pilot switching valve for the boom further has a boom-raising pilot port. The hydraulic excavator further includes: a boom-raising pilot conduit; a boom-raising proportional solenoid valve; and a second pressure sensor. The boom-raising pilot conduit is connected to the boom-raising pilot port. The boom-raising proportional solenoid valve is provided in the boom-raising pilot conduit. The second pressure sensor detects a pressure generated in the boom-raising pilot conduit between the control lever and the boom-raising proportional solenoid valve. The controller controls an opening degree of the boom-raising proportional solenoid valve based on the pressure detected by the second pressure sensor. The amount of increase in current per unit time when the controller outputs, to the boom-lowering proportional solenoid valve, the instruction signal for instructing an increase in opening degree is smaller than an amount of increase in current per unit time when the controller outputs, to the boom-raising proportional solenoid valve, an instruction signal for instructing an increase in opening degree. Thus, the response speed of the boom-lowering operation can be decreased while maintaining the response speed of the boom-raising operation.
The hydraulic excavator further includes a bucket having a cutting edge. The controller controls the boom to prevent a position of the cutting edge from becoming lower than construction design data. Thus, the land leveling work can be performed in accordance with the construction design data, and therefore, the quality and efficiency of the land leveling work with the hydraulic excavator can be enhanced.
In the hydraulic excavator, the controller transmits and receives information to and from the outside by satellite communication. Thus, the information-oriented construction based on the information transmitted and received to and from the outside becomes possible, and the highly-efficient and highly-accurate land leveling work with the hydraulic excavator can be realized.
As described above, according to the present invention, even when the vehicle body shakes after the work implement stops automatically, in the case of aligning the cutting edge of the bucket with the design surface, it is possible to suppress execution of boom-lowering again when the cutting edge temporarily moves upwardly away from the design surface. Therefore, it is possible to prevent the problem that the cutting edge is located lower than the design surface and the design surface is invaded after the shake of the vehicle body stops.
An embodiment of the present invention will be described hereinafter with reference to the drawings.
First, a configuration of a hydraulic excavator to which an idea of the present invention is applicable will be described.
Undercarriage 2 has a pair of left and right crawler belts. It is configured to allow hydraulic excavator 1 to be self-propelled by rotation of the pair of crawler belts. Upper revolving unit 3 is disposed to be pivotable with respect to undercarriage 2.
Upper revolving unit 3 includes a cab 4 that is a space for an operator to operate hydraulic excavator 1. Cab 4 is included in the work vehicle main body. On the backward side B, upper revolving unit 3 includes an engine compartment that houses an engine, and a counter weight. In the present embodiment, the frontward side (front side) of the operator when seated in cab 4 will be referred to as frontward side F of upper revolving unit 3, and the side opposite to frontward side F, i.e., the backward side of the operator will be referred to as backward side B of upper revolving unit 3. The left side of the operator when seated will be referred to as left side L of upper revolving unit 3, and the right side of the operator when seated will be referred to as right side R of upper revolving unit 3. In the following description, it is assumed that the frontward-backward and left-right directions of upper revolving unit 3 match the frontward-backward and left-right directions of hydraulic excavator 1.
Work implement 5 that performs works such as soil excavation is pivotably supported by upper revolving unit 3 so as to be operable in the upward-downward direction. Work implement 5 has a boom 6 attached to a substantially central portion on frontward side F of upper revolving unit 3 so as to be operable in the upward-downward direction, an arm 7 attached to a tip of boom 6 so as to be operable in the backward-frontward direction, and a bucket 8 attached to a tip of arm 7 so as to be operable in the backward-frontward direction. Bucket 8 has a cutting edge 8a at a tip thereof. Boom 6, arm 7 and bucket 8 are configured to be driven by a boom cylinder 9, an arm cylinder 10 and a bucket cylinder 11 that are hydraulic cylinders, respectively.
Cab 4 is arranged on frontward side F and on left side L of upper revolving unit 3. With respect to cab 4, work implement 5 is provided on right side R that is one side portion side of cab 4. It should be noted that the arrangement of cab 4 and work implement 5 is not limited to the example shown in
A space surrounded by each pillar and the floor and roof portions of cab 4 forms an interior space of cab 4. Operator's seat 24 is housed in the interior space of cab 4 and is arranged at a substantially center of the floor portion of cab 4. A side surface on left side L of cab 4 is provided with a door for the operator to get in or out of cab 4.
A front window is arranged on frontward side F with respect to operator's seat 24. The front window is made of a transparent material and the operator seated on operator's seat 24 can view the outside of cab 4 through the front window. For example, as shown in
A monitor device 26 is disposed on frontward side F inside cab 4. Monitor device 26 is arranged at a corner on the frontward right side inside cab 4, and is supported by a support extending from the floor portion of cab 4. Monitor device 26 is arranged on the operator's seat 24 side with respect to the front pillar. Monitor device 26 is arranged in front of the front pillar when viewed from the operator seated on operator's seat 24.
For multipurpose use, monitor device 26 includes a planar display surface 26d having various monitor functions, a switch unit 27 having a plurality of switches to which many functions are assigned, and a sound generator 28 that expresses by sound the contents displayed on display surface 26d. This display surface 26d is configured by a graphic indicator such as a liquid crystal indicator and an organic EL indicator. Although switch unit 27 includes a plurality of key switches, the present invention is not limited thereto. Switch unit 27 may include touch panel-type touch switches.
Travel control levers (left and right travel control levers) 22a and 22b for the left and right crawler belts are provided on frontward side F of operator's seat 24. Left and right travel control levers 22a and 22b form a travel control unit 22 for controlling undercarriage 2.
A first control lever 44 for the operator on cab 4 to control driving of boom 6 and bucket 8 of work implement 5 is provided on right side R of operator's seat 24. A switch panel 29 having various switches and the like mounted thereon is also provided on right side R of operator's seat 24. A second control lever 45 for the operator to control driving of arm 7 of work implement 5 and revolving of upper revolving unit 3 is provided on left side L of operator's seat 24.
A monitor 21 is arranged above monitor device 26. Monitor 21 has a planar display surface 21d. Comparing display surface 26d of monitor device 26 and display surface 21d of monitor 21 shown in
Monitor 21 is attached to the front pillar on right side R, which is the side close to work implement 5, of the pair of front pillars. Monitor 21 is arranged in front of the front pillar in the line of sight of the operator seated on operator's seat 24 toward the frontward right direction. By attaching monitor 21 to the front pillar on right side R in hydraulic excavator 1 including work implement 5 on right side R of cab 4, the operator can view both work implement 5 and monitor 21 with a small amount of line-of-sight movement.
Information can be transmitted and received between controller 20 and an external monitoring station 96. In the present embodiment, controller 20 and monitoring station 96 communicate with each other by satellite communication. A communication terminal 91 having a satellite communication antenna 92 is connected to controller 20. As shown in
An example of applying the information-oriented construction system to hydraulic excavator 1 according to the present embodiment will be described. Construction design data created by a three-dimensional CAD (Computer Aided Design) is prestored in controller 20. Monitor 21 updates and displays the externally-received current position of hydraulic excavator 1 on the screen in real time, such that the operator can constantly check the work state of hydraulic excavator 1.
Controller 20 compares the construction design data with the position and posture of work implement 5 in real time, and drives a hydraulic circuit based on the result of comparison, thereby controlling work implement 5. More specifically, controller 20 compares the position for construction based on the construction design data (design surface) with the position of bucket 8, and executes control to prevent cutting edge 8a of bucket 8 from being located lower than the design surface to prevent deeper excavation than the design surface. As a result, the construction efficiency and the construction accuracy can be enhanced, and high-quality construction can be easily performed.
Main operation valve 34 has a pilot switching valve for the arm 36, a pilot switching valve for the boom 37, a pilot switching valve for left travel 38, a pilot switching valve for right travel 39, and a pilot switching valve for the bucket 40. Pilot switching valve for the arm 36 controls supply and discharge of the hydraulic oil to and from arm cylinder 10. Pilot switching valve for the boom 37 controls supply and discharge of the hydraulic oil to and from boom cylinder 9. Pilot switching valve for left travel 38 controls supply and discharge of the hydraulic oil to and from left travel motor 17. Pilot switching valve for right travel 39 controls supply and discharge of the hydraulic oil to and from right travel motor 16. Pilot switching valve for the bucket 40 controls supply and discharge of the hydraulic oil to and from bucket cylinder 11.
Each of pilot switching valve for the arm 36, pilot switching valve for the boom 37, pilot switching valve for left travel 38, pilot switching valve for right travel 39, and pilot switching valve for the bucket 40 has a pair of pilot ports p1 and p2. In accordance with the pressure (pilot pressure) of the oil supplied to each of pilot ports p1 and p2, each of pilot switching valves 36 to 40 is controlled.
The pilot pressures applied to pilot ports p1 and p2 of pilot switching valve for the arm 36, pilot switching valve for the boom 37 and pilot switching valve for the bucket 40 are controlled by operating a first control lever device 41 and a second control lever device 42. The pilot pressures applied to pilot switching valve for left travel 38 and pilot switching valve for right travel 39 are controlled by operating left and right travel control levers 22a and 22b shown in
First control lever device 41 has first control lever 44 operated by the operator, a first pilot pressure control valve 41A, a second pilot pressure control valve 41B, a third pilot pressure control valve 41C, and a fourth pilot pressure control valve 41D. First pilot pressure control valve 41A, second pilot pressure control valve 41B, third pilot pressure control valve 41C, and fourth pilot pressure control valve 41D are provided to correspond to the four directions, i.e., the frontward-backward and left-right directions, of first control lever 44.
Second control lever device 42 has second control lever 45 operated by the operator, a fifth pilot pressure control valve 42A, a sixth pilot pressure control valve 42B, a seventh pilot pressure control valve 42C, and an eighth pilot pressure control valve 42D. Fifth pilot pressure control valve 42A, sixth pilot pressure control valve 42B, seventh pilot pressure control valve 42C, and eighth pilot pressure control valve 42D are provided to correspond to the four directions, i.e., the frontward-backward and left-right directions, of second control lever 45.
Pilot pressure control valves 41A to 41D and 42A to 42D for controlling driving of hydraulic cylinders 9, 10 and 11 for work implement 5 as well as a swing motor are connected to first control lever 44 and second control lever 45, respectively. Pilot pressure control valves for controlling driving of right and left travel motors 16 and 17 are connected to left and right travel control levers 22a and 22b, respectively.
First pilot pressure control valve 41A has a first pump port X1, a first tank port Y1 and a first supply/discharge port Z1. First pump port X1 is connected to a pump flow path 51. First tank port Y1 is connected to a tank flow path 52. Pump flow path 51 and tank flow path 52 are connected to tank 35 that stores the hydraulic oil. A third hydraulic pump 50 is provided in pump flow path 51. Third hydraulic pump 50 is different from first hydraulic pump 31 and second hydraulic pump 32 described above. However, instead of third hydraulic pump 50, first hydraulic pump 31 or second hydraulic pump 32 may be used. First supply/discharge port Z1 is connected to a first pilot conduit 53.
In accordance with the operation of first control lever 44, first pilot pressure control valve 41A is switched between an output state and a discharge state. In the output state, first pilot pressure control valve 41A causes first pump port X1 and first supply/discharge port Z1 to communicate with each other, and outputs the hydraulic oil having a pressure corresponding to an amount of operation of first control lever 44 from first supply/discharge port Z1 to first pilot conduit 53. In the discharge state, first pilot pressure control valve 41A causes first tank port Y1 and first supply/discharge port Z1 to communicate with each other.
Second pilot pressure control valve 41B has a second pump port X2, a second tank port Y2 and a second supply/discharge port Z2. Second pump port X2 is connected to pump flow path 51. Second tank port Y2 is connected to tank flow path 52. Second supply/discharge port Z2 is connected to a second pilot conduit 54.
In accordance with the operation of first control lever 44, second pilot pressure control valve 41B is switched between an output state and a discharge state. In the output state, second pilot pressure control valve 41B causes second pump port X2 and second supply/discharge port Z2 to communicate with each other, and outputs the hydraulic oil having a pressure corresponding to an amount of operation of first control lever 44 from second supply/discharge port Z2 to second pilot conduit 54. In the discharge state, second pilot pressure control valve 41B causes second tank port Y2 and second supply/discharge port Z2 to communicate with each other.
First pilot pressure control valve 41A and second pilot pressure control valve 41B form a pair and correspond to the operation directions of first control lever 44 that are opposite to each other. For example, first pilot pressure control valve 41A corresponds to the operation of first control lever 44 toward the frontward direction, and second pilot pressure control valve 41B corresponds to the operation of first control lever 44 toward the backward direction. Either first pilot pressure control valve 41A or second pilot pressure control valve 41B is selected in accordance with the operation of first control lever 44. When first pilot pressure control valve 41A is in the output state, second pilot pressure control valve 41B is in the discharge state. When first pilot pressure control valve 41A is in the discharge state, second pilot pressure control valve 41B is in the output state.
First pilot pressure control valve 41A controls supply and discharge of the hydraulic oil to and from second pilot port p2 of pilot switching valve for the boom 37. Second pilot pressure control valve 41B controls supply and discharge of the hydraulic oil to and from first pilot port p1 of pilot switching valve for the boom 37. In accordance with the operation of first control lever 44, supply and discharge of the hydraulic oil to and from boom cylinder 9 are controlled, and extension and contraction of boom cylinder 9 are controlled. As a result, the operation for raising or lowering boom 6 is controlled in accordance with the operation of first control lever 44.
First pilot port p1 of pilot switching valve for the boom 37 has a function as a boom-raising pilot port supplied with the hydraulic oil at the time of the operation for raising boom 6. Second pilot port p2 of pilot switching valve for the boom 37 has a function as a boom-lowering pilot port supplied with the hydraulic oil at the time of the operation for lowering boom 6.
The pilot pressure supplied to first pilot conduit 53 via first pilot pressure control valve 41A is detected by a hydraulic pressure sensor 63. Hydraulic pressure sensor 63 outputs, to controller 20, a pressure signal P3 that is an electric detection signal corresponding to the detected pilot pressure. In addition, the pilot pressure supplied to second pilot conduit 54 via second pilot pressure control valve 41B is detected by a hydraulic pressure sensor 64. Hydraulic pressure sensor 64 outputs, to controller 20, a pressure signal P4 that is an electric detection signal corresponding to the detected pilot pressure.
A relay block 70 is provided in a hydraulic pressure path connecting first and second control lever devices 41 and 42 and main operation valve 34. Relay block 70 is configured to include a plurality of proportional solenoid valves 73 to 79. Proportional solenoid valve 73 is provided in first pilot conduit 53. Hydraulic pressure sensor 63 is provided between first pilot pressure control valve 41A and proportional solenoid valve 73 in first pilot conduit 53. Proportional solenoid valve 74 is provided in second pilot conduit 54. Hydraulic pressure sensor 64 is provided between second pilot pressure control valve 41B and proportional solenoid valve 74 in second pilot conduit 54. Proportional solenoid valves 73 and 74 are provided to control the operation for moving boom 6 upwardly and downwardly in accordance with the operation of first control lever 44.
Based on the pilot pressure of first pilot conduit 53 detected by hydraulic pressure sensor 63, controller 20 controls proportional solenoid valve 73. Hydraulic pressure sensor 63 has a function as a first pressure sensor for detecting the hydraulic pressure generated in first pilot conduit 53 between first pilot pressure control valve 41A and proportional solenoid valve 73 in accordance with the operation of first control lever 44. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 63, controller 20 outputs an instruction signal G3 to proportional solenoid valve 73 and adjusts the opening degree thereof, thereby changing a flow rate of the hydraulic oil flowing through first pilot conduit 53, and controlling the hydraulic pressure transmitted to second pilot port p2 of pilot switching valve for the boom 37.
Based on the hydraulic pressure detected by hydraulic pressure sensor 63, controller 20 controls the opening degree of proportional solenoid valve 73 and outputs, to proportional solenoid valve 73, an instruction signal for instructing boom-lowering. In accordance with the degree of the hydraulic pressure transmitted to second pilot port p2, the speed of boom 6 when lowered is adjusted.
In addition, based on the pilot pressure of second pilot conduit 54 detected by hydraulic pressure sensor 64, controller 20 controls proportional solenoid valve 74. Hydraulic pressure sensor 64 has a function as a second pressure sensor for detecting the hydraulic pressure generated in second pilot conduit 54 between second pilot pressure control valve 41B and proportional solenoid valve 74 in accordance with the operation of first control lever 44. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 64, controller 20 outputs an instruction signal. G4 to proportional solenoid valve 74 and adjusts the opening degree thereof, thereby changing a flow rate of the hydraulic oil flowing through second pilot conduit 54, and controlling the hydraulic pressure transmitted to first pilot port p1 of pilot switching valve for the boom 37.
Based on the hydraulic pressure detected by hydraulic pressure sensor 64, controller 20 controls the opening degree of proportional solenoid valve 74 and outputs, to proportional solenoid valve 74, an instruction signal for instructing boom-raising. In accordance with the degree of the hydraulic pressure transmitted to first pilot port p1, the speed of boom 6 when raised is adjusted.
A shuttle valve 80 is provided in second pilot conduit 54. Shuttle valve 80 has two entrance ports and one exit port. The exit port of shuttle valve 80 is connected to first pilot port p1 of pilot switching valve for the boom 37 via second pilot conduit 54. One entrance port of shuttle valve 80 is connected to second pilot pressure control valve 41B via second pilot conduit 54. The other entrance port of shuttle valve 80 is connected to a pump flow path 55.
Pump flow path 55 branches off from pump flow path 51. One end of pump flow path 55 is connected to pump flow path 51 and the other end of pump flow path 55 is connected to shuttle valve 80. The hydraulic oil transported by third hydraulic pump 50 flows to first control lever device 41 and second control lever device 42 via pump flow path 51, and also flows to shuttle valve 80 via pump flow paths 51 and 55.
Shuttle valve 80 is a shuttle valve of higher pressure priority type. Shuttle valve 80 compares the hydraulic pressure in second pilot conduit 54 connected to one entrance port and the hydraulic pressure in pump flow path 55 connected to the other entrance port, and selects the higher pressure. Shuttle valve 80 causes a higher pressure-side flow path of second pilot conduit 54 and pump flow path 55 to communicate with the exit port, and supplies the hydraulic oil flowing through this higher pressure-side flow path to first pilot port p1 of pilot switching valve for the boom 37.
A proportional solenoid valve 75 included in relay block. 70 is provided in pump flow path 55. Proportional solenoid valve 75 is a valve for forcible boom-raising intervention. Proportional solenoid valve 75 receives an instruction signal G5 outputted from controller 20, and adjusts the opening degree thereof. Regardless of the operation of first control lever device 41 by the operator, controller 20 outputs instruction signal G5 to proportional solenoid valve 75 and adjusts the opening degree thereof, thereby changing a flow rate of the hydraulic oil flowing through pump flow path 55, and controlling the hydraulic pressure transmitted to first pilot port p1 of pilot switching valve for the boom 37. By adjustment of the opening degree of proportional solenoid valve 75, controller 20 controls the operation for forcibly raising boom 6.
Third pilot pressure control valve 41C and fourth pilot pressure control valve 41D have configurations similar to those of first pilot pressure control valve 41A and second pilot pressure control valve 41B described above. Similarly to first pilot pressure control valve 41A and second pilot pressure control valve 41B, third pilot pressure control valve 41C and fourth pilot pressure control valve 41D form a pair, and either third pilot pressure control valve 41C or fourth pilot pressure control valve 41D is selected in accordance with the operation of first control lever 44. For example, third pilot pressure control valve 41C corresponds to the operation of first control lever 44 toward the left direction, and fourth pilot pressure control valve 41D corresponds to the operation of first control lever 44 toward the right direction.
Third pilot pressure control valve 41C is connected to pump flow path 51, tank flow path 52 and a third pilot conduit 56. Third pilot pressure control valve 41C controls supply and discharge of the hydraulic oil to and from second pilot port p2 of pilot switching valve for the bucket 40. Fourth pilot pressure control valve 41D is connected to pump flow path 51, tank flow path 52 and a fourth pilot conduit 57. Fourth pilot pressure control valve 41D controls supply and discharge of the hydraulic oil to and from first pilot port p1 of pilot switching valve for the bucket 40. In accordance with the operation of first control lever 44, supply and discharge of the hydraulic oil to and from bucket cylinder 11 are controlled, and extension and contraction of bucket cylinder 11 are controlled. As a result, the operation of bucket 8 toward the excavation direction or the open direction is controlled in accordance with the operation of first control lever 44.
The pressure (pilot pressure) of the hydraulic oil supplied to third pilot conduit 56 via third pilot pressure control valve 41C is detected by a hydraulic pressure sensor 66. Hydraulic pressure sensor 66 outputs, to controller 20, a pressure signal P6 corresponding to the detected pilot pressure of the hydraulic oil. A proportional solenoid valve 76 is provided in third pilot conduit 56 connecting third pilot pressure control valve 41C and second pilot port p2 of pilot switching valve for the bucket 40. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 66, controller 20 outputs an instruction signal G6 to proportional solenoid valve 76, and controls the hydraulic pressure transmitted to second pilot port p2 of pilot switching valve for the bucket 40. In accordance with the degree of the hydraulic pressure transmitted to second pilot port p2, the speed of bucket 8 when moved toward the excavation direction is adjusted.
The pressure (pilot pressure) of the hydraulic oil supplied to fourth pilot conduit 57 via fourth pilot pressure control valve 41D is detected by a hydraulic pressure sensor 67. Hydraulic pressure sensor 67 outputs, to controller 20, a pressure signal P7 corresponding to the detected pilot pressure of the hydraulic oil. A proportional solenoid valve 77 is provided in fourth pilot conduit 57 connecting fourth pilot pressure control valve 41D and first pilot port p1 of pilot switching valve for the bucket 40. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 67, controller 20 outputs an instruction signal G7 to proportional solenoid valve 77, and controls the hydraulic pressure transmitted to first pilot port p1 of pilot switching valve for the bucket 40. In accordance with the degree of the hydraulic pressure transmitted to first pilot port p1, the speed of bucket 8 when moved toward the open direction is adjusted.
Fifth pilot pressure control valve 42A, sixth pilot pressure control valve 42B, seventh pilot pressure control valve 42C, and eighth pilot pressure control valve 42D have configurations similar to those of first pilot pressure control valve 41A, second pilot pressure control valve 41B, third pilot pressure control valve 41C, and fourth pilot pressure control valve 41D described above. Fifth pilot pressure control valve 42A and sixth pilot pressure control valve 42B form a pair, and either fifth pilot pressure control valve 42A or sixth pilot pressure control valve 42B is selected in accordance with the operation of second control lever 45. Seventh pilot pressure control valve 42C and eighth pilot pressure control valve 42D form a pair, and either seventh pilot pressure control valve 42C or eighth pilot pressure control valve 42D is selected in accordance with the operation of second control lever 45.
For example, fifth pilot pressure control valve 42A corresponds to the operation of second control lever 45 toward the frontward direction, and sixth pilot pressure control valve 42B corresponds to the operation of second control lever 45 toward the backward direction. Seventh pilot pressure control valve 42C corresponds to the operation of second control lever 45 toward the left direction, and eighth pilot pressure control valve 42D corresponds to the operation of second control lever 45 toward the right direction.
Fifth pilot pressure control valve 42A is connected to pump flow path 51, tank flow path 52 and a fifth pilot conduit 60. Sixth pilot pressure control valve 42B is connected to pump flow path 51, tank flow path 52 and a sixth pilot conduit 61. A not-shown electric motor for revolving upper revolving unit 3 is controlled based on the pressure of the hydraulic oil supplied to fifth pilot conduit 60 via fifth pilot pressure control valve 42A and the pressure of the hydraulic oil supplied to sixth pilot conduit 61 via sixth pilot pressure control valve 42B. Rotational driving of this electric motor when the hydraulic oil is supplied to fifth pilot conduit 60 is opposite to rotational driving of the electric motor when the hydraulic oil is supplied to sixth pilot conduit 61. In accordance with the direction of operation and the amount of operation of second control lever 45, the revolving direction and the revolving speed of upper revolving unit 3 are controlled.
Seventh pilot pressure control valve 42C is connected to pump flow path 51, tank flow path 52 and a seventh pilot conduit 58. Seventh pilot pressure control valve 42C controls supply and discharge of the hydraulic oil to and from first pilot port p1 of pilot switching valve for the arm 36. Eighth pilot pressure control valve 42D is connected to pump flow path 51, tank flow path 52 and an eighth pilot conduit 59. Eighth pilot pressure control valve 42D controls supply and discharge of the hydraulic oil to and from second pilot port p2 of pilot switching valve for the arm 36. In accordance with the operation of second control lever 45, supply and discharge of the hydraulic oil to and from arm cylinder 10 are controlled, and extension and contraction of arm cylinder 10 are controlled. As a result, the operation for relatively rotating arm 7 with respect to boom 6 is controlled in accordance with the operation of second control lever 45.
The pressure (pilot pressure) of the hydraulic oil supplied to seventh pilot conduit 58 via seventh pilot pressure control valve 42C is detected by a hydraulic pressure sensor 68. Hydraulic pressure sensor 68 outputs, to controller 20, a pressure signal P8 corresponding to the detected pilot pressure of the hydraulic oil. A proportional solenoid valve 78 is provided in seventh pilot conduit 58 connecting seventh pilot pressure control valve 42C and first pilot port p1 of pilot switching valve for the arm 36. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 68, controller 20 outputs an instruction signal G8 to proportional solenoid valve 78, and controls the hydraulic pressure transmitted to first pilot port p1 of pilot switching valve for the arm 36. In accordance with the degree of the hydraulic pressure transmitted to first pilot port p1, the speed of arm 7 when moved toward the direction of extending arm 7, i.e., toward the direction in which arm 7 moves away from upper revolving unit 3, is adjusted.
The pressure (pilot pressure) of the hydraulic oil supplied to eighth pilot conduit 59 via eighth pilot pressure control valve 42D is detected by a hydraulic pressure sensor 69. Hydraulic pressure sensor 69 outputs, to controller 20, a pressure signal P9 corresponding to the detected pilot pressure of the hydraulic oil. A proportional solenoid valve 79 is provided in eighth pilot conduit 59 connecting eighth pilot pressure control valve 42D and second pilot port p2 of pilot switching valve for the arm 36. In accordance with the hydraulic pressure detected by hydraulic pressure sensor 69, controller 20 outputs an instruction signal G9 to proportional solenoid valve 79, and controls the hydraulic pressure transmitted to second pilot port p2 of pilot switching valve for the arm 36. In accordance with the degree of the hydraulic pressure transmitted to second pilot port p2, the speed of arm 7 when moved toward the direction of bending arm 7, i.e., toward the direction in which arm 7 comes closer to upper revolving unit 3, is adjusted.
The setting of a correspondence relationship between the operation directions of first and second control levers 44 and 45 and the operation of work implement 5 and the revolving operation of upper revolving unit 3 may be switchable to desired patterns. For example, first pilot pressure control valve 41A and second pilot pressure control valve 41B may correspond to the operations of first control lever 44 toward the frontward and backward directions, respectively, or may correspond to the operations of first control lever 44 toward the left and right directions, respectively.
The land leveling work with hydraulic excavator 1 having the aforementioned configuration will be described below.
When cutting edge 8a of bucket 8 is aligned with design surface S from the state in which work implement 5 is located above design surface S as shown in
In order to avoid cutting edge 8a of bucket 8 from moving to be lower than design surface S and cutting into design surface S, control for automatically stopping the operation of work implement 5 at a position where cutting edge 8a comes into contact with design surface S is executed. When it is expected that cutting edge 8a of bucket 8 will move to be lower than design surface S, controller 20 executes stop control for automatically stopping boom 6 to prevent cutting edge 8a of bucket 8 from becoming lower than design surface S. At this time, controller 20 outputs instruction signal G3 for decreasing the opening degree of proportional solenoid valve 73. As a result, proportional solenoid valve 73 that has been in the open state enters the fully-closed state. As described above, cutting edge 8a of bucket 8 is aligned with design surface S as shown in
First pilot conduit 53 has a function as a boom-lowering pilot conduit connected to second pilot port p2 of pilot switching valve for the boom 37. Second pilot conduit 54 and pump flow path 55 have a function as a boom-raising pilot conduit connected to first pilot port p1 of pilot switching valve for the boom 37 via shuttle valve 80. Proportional solenoid valve 73 provided in first pilot conduit 53 has a function as a boom-lowering proportional solenoid valve. Proportional solenoid valve 74 provided in second pilot conduit 54 has a function as a boom-raising proportional solenoid valve. Proportional solenoid valve 75 provided in pump flow path 55 has a function as a boom-raising proportional solenoid valve.
Both second pilot conduit 54 and pump flow path 55 have a function as a boom-raising pilot conduit. More specifically, second pilot conduit 54 functions as a normal boom-raising pilot conduit, and pump flow path 55 functions as a forcible boom-raising pilot conduit. In addition, proportional solenoid valve 74 can be expressed as a normal boom-raising proportional solenoid valve, and proportional solenoid valve 75 can be expressed as a forcible boom-raising proportional solenoid valve.
Hydraulic pressure sensor 63 detects the hydraulic pressure generated in first pilot conduit 53 between first pilot pressure control valve 41A and proportional solenoid valve 73 in accordance with the operation of first control lever 44. Based on the hydraulic pressure detected by hydraulic pressure sensor 63, controller 20 outputs instruction signal G3 to proportional solenoid valve 73 and controls the opening degree of proportional solenoid valve 73. Hydraulic pressure sensor 64 detects the hydraulic pressure generated in second pilot conduit 54 between second pilot pressure control valve 41B and proportional solenoid valve 74 in accordance with the operation of first control lever 44. Based on the hydraulic pressure detected by hydraulic pressure sensor 64, controller 20 outputs instruction signal G4 to proportional solenoid valve 74 and controls the opening degree of proportional solenoid valve 74. Controller 20 outputs instruction signal G5 to proportional solenoid valve 75 and controls the opening degree of proportional solenoid valve 75.
As shown in the upper graph in
At this time, the operator operating hydraulic excavator 1 continues to operate first control lever 44 toward the boom-lowering side until work implement 5 stops automatically. In addition, the operator gradually decreases the inclination angle of first control lever 44 and decreases the boom-lowering EPC current such that the movement speed of work implement 5 becomes lower as cutting edge 8a of bucket 8 comes closer to design surface S. As a result, precise alignment of cutting edge 8a of bucket 8 with design surface S becomes possible, and shock when boom 6 stops automatically is absorbed.
When control for automatically stopping boom 6 at design surface S is executed, the relative movement speed of work implement 5 with respect to the work vehicle main body of hydraulic excavator 1 changes suddenly, and thus, the work vehicle main body of hydraulic excavator 1 shakes. Due to this shake, the distance between cutting edge 8a of bucket 8 and design surface S increases again as shown in the upper graph in
Hydraulic excavator 1 according to the present embodiment has been made to solve this phenomenon.
The lower graph in
The graph in
The amount of increase in current per unit time will be described.
From the foregoing, the amount of increase in current per unit time is calculated in accordance with the following equation:
(amount of increase in current per unit time)=(i2−i1)/(t2−t1).
The amount of decrease in current per unit time will be described.
From the foregoing, the amount of decrease in current per unit time is calculated in accordance with the following equation:
(amount of decrease in current per unit time)=(i3−i4)/(t4−t3).
Next, the function and effect of the present embodiment will be described.
According to the present embodiment, as shown in
The graph before the present invention is applied as shown in
Proportional solenoid valve 73 is configured such that the opening operation starts when the current value increases from zero to a prescribed threshold value in the case of increasing the opening degree from the fully-closed state. Proportional solenoid valve 73 may be configured such that the opening operation starts when the boom-lowering EPC current increases to 40% of the rated current. To proportional solenoid valve 73 having such a configuration, controller 20 outputs the gently-increasing current value. As a result, the response speed of the operation for lowering boom 6 with respect to the operator's operation can be decreased.
For example, in the time period during which the boom-lowering EPC current is increasing as shown in
Therefore, even if cutting edge 8a of bucket 8 temporarily moves away from design surface S due to the shake of the work vehicle main body, boom 6 does not move and the relative position of work implement 5 with respect to the work vehicle main body can be maintained. Since it is possible to suppress execution of boom-lowering again when the work vehicle main body shakes, it is possible to prevent cutting edge 8a of bucket 8 from being located lower than design surface S and invading design surface S.
In addition, as shown in
As described above, by reducing the rate of increase in current when proportional solenoid valve 73 is opened, invasion of design surface S by work implement 5 can be prevented. On the other hand, by relatively increasing a rate of decrease in current when proportional solenoid valve 73 is closed as compared with the rate of increase in current when proportional solenoid valve 73 is opened, the valve closing speed of proportional solenoid valve 73 becomes relatively high.
The case of closing proportional solenoid valve 73 during automatic control corresponds to the case in which cutting edge 8a of bucket 8 comes sufficiently close to design surface S and the instruction for lowering boom 6 is no longer necessary. In this case, it is desirable to shorten the time to continue the operation for lowering boom 6 and immediately stop the operation for lowering boom 6. By relatively increasing the valve closing speed of proportional solenoid valve 73, the operation for lowering boom 6 can be stopped immediately, and thus, excessive excavation with respect to design surface S can be avoided more reliably. Therefore, the efficiency and quality during the work for leveling the ground with hydraulic excavator 1 can be enhanced.
In addition, as shown in
As described above, by reducing the rate of increase in current when proportional solenoid valve 73 is opened, invasion of design surface S by work implement 5 can be prevented. On the other hand, by relatively increasing a rate of increase in current when proportional solenoid valve 74 or 75 is opened as compared with the rate of increase in current when proportional solenoid valve 73 is opened, the valve opening speed of proportional solenoid valve 74 or 75 becomes relatively high. By increasing the sensitivity of proportional solenoid valve 74 or 75, boom 6 can be immediately raised when the operator performs the boom-raising operation.
If the rate of increase in current when the opening degree of proportional solenoid valve 73 is increased is reduced excessively, the responsiveness to the operator's operation decreases. Therefore, it takes time from when the operator operates first control lever 44 to when boom 6 operates, and the operator may feel that the operation of boom 6 is slow and may feel stress. Thus, it is desirable to reduce the rate of increase in current when the opening degree of proportional solenoid valve 73 is increased, so as not to affect the responsiveness of the operation of work implement 5 at the time of manual operation. For example, the rate of increase in current when the opening degree of proportional solenoid valve 73 is increased may be set to fall within 1/100 times or more and ½ times or less of a rate of change in current when the opening degree of proportional solenoid valve 73 is decreased or when the opening degree of proportional solenoid valve 74 or 75 is increased.
It should be understood that the embodiment disclosed herein is illustrative and not limitative in any respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
1 hydraulic excavator; 2 undercarriage; 3 upper revolving unit; 4 cab; 5 work implement; 6 boom; 7 arm; 8 bucket; 8a cutting edge; 9 boom cylinder; 20 controller; 34 main operation valve; 35 tank; 37 pilot switching valve for the boom; 41 first control lever device; 41A to 41D, 42A to 42D pilot pressure control valve; 42 second control lever device; 44 first control lever; 45 second control lever; 50 third hydraulic pump; 51, 55 pump flow path; 52 tank flow path; 53, 54, 56 to 61 pilot conduit; 63, 64, 66 to 69 hydraulic pressure sensor; 70 relay block; 73 to 79 proportional solenoid valve; 80 shuttle valve; G3 to G9 instruction signal; P3, P4, P6 to P9 pressure signal; S design surface; p1 first pilot port; p2 second pilot port.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/082825 | Dec 2013 | WO | international |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/061537 | 4/24/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/192473 | 12/4/2014 | WO | A |
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| 20150240446 A1 | Aug 2015 | US |
