Patent Application
20210332563
The present invention relates to a construction machine having a machine control function.
In association with responding to information-oriented working, among construction machines such as hydraulic excavators, there are ones having a machine control function that controls the position and posture of work mechanisms such as boom, arm, and bucket in such a manner that the work mechanisms move along a target working surface. As representative one thereof, what limits operation of the work mechanisms in such a manner that the bucket tip does not advance in the direction of the target working surface any more when the bucket tip approaches the target working surface is known.
In standards of civil engineering works execution management, a standard value of the acceptable accuracy in the height direction with respect to the target working surface is defined. When the accuracy of the finished shape of the working surface exceeds the acceptable value, redoing of working occurs and thus the work efficiency lowers. Therefore, the machine control function is required to have the control accuracy necessary to meet the acceptable accuracy of the finished shape.
In association with a spread of the machine control function, development of a function of holding or correcting the bucket angle or the tilt angle with respect to the target working surface is being advanced. Due to this, in the case in which the bucket angle or the tilt angle needs to be held or corrected, the number of hydraulic actuators that need to be simultaneously controlled by the machine control function increases compared with a conventional machine control function that merely carries out combined operation of arm and boom, and it is required to control plural hydraulic actuators simultaneously and accurately.
As one of general methods for improving the control accuracy of the hydraulic actuator, there are methods using feedback control in which the flow rate of inflow to the hydraulic actuator is estimated and the error from a target inflow flow rate is corrected. However, in these control methods, control of the flow rate of inflow to a single hydraulic actuator is assumed in many methods, whereas control of the flow rate of inflow to plural hydraulic actuators through flow dividing is assumed in a small number of methods.
A technique in which flow dividing into plural hydraulic actuators is assumed and a hydraulic pump is electronically controlled on the basis of an estimated inflow flow rate is disclosed in patent document 1. In a control system of a hydraulic excavator shown in patent document 1, at the time of flow dividing control of the hydraulic actuators, the inflow flow rate is controlled by the hydraulic pump regarding a high-load-side hydraulic actuator with a high load and the inflow flow rate is controlled by a pressure compensating valve and a meter-in valve regarding a low-load-side hydraulic actuator with a low load. At this time, the target delivery flow rate of the hydraulic pump is corrected on the basis of the estimated inflow flow rate.
The control system of patent document 1 causes the estimation result of the inflow flow rate to be reflected in control of the delivery flow rate of the hydraulic pump. However, the leakage of the inflow flow rate, the influence of flow rate loss due to compression, and characteristics of the mater-in valve differ for each actuator section. Therefore, flow rate errors different for each actuator section are caused. For this reason, it is impossible to correct the flow rate errors of all actuator sections by only correcting the delivery flow rate of the hydraulic pump existing on the most upstream side of the hydraulic circuit. Therefore, for improving the flow rate control accuracy also at the time of flow dividing, the opening amount of the meter-in valve of the hydraulic actuator that operates needs to be directly corrected individually.
In the case of directly correcting the opening amount of the meter-in valve on the basis of the estimated inflow flow rate, interference with the delivery flow rate control of the hydraulic pump needs to be avoided. When both the opening amount of the meter-in valve and the delivery flow rate of the hydraulic pump are corrected on the basis of the estimated inflow flow rate, if the degree of correction is high, there is a possibility that interference of the control of the opening amount and the delivery flow rate occurs and hunting occurs in the inflow flow rate. In contrast, if the degree of correction is low, convergence of the actual inflow flow rate to the hydraulic actuator on the target inflow flow rate is delayed and therefore performance of transient following for the target inflow flow rate lowers.
Furthermore, if the delivery flow rate from the hydraulic pump is insufficient with respect to the target inflow flow rate when the opening amount of the mater-in valve is directly corrected on the basis of the estimated inflow flow rate, an error is generated between the target inflow flow rate and the actual inflow flow rate. In this case, the opening amounts of all meter-in valves become larger than the target value and thus distribution control of the inflow flow rate becomes difficult. Therefore, it is desirable to correct only the opening amount of the mater-in valve with avoidance of the situation in which the delivery flow rate from the hydraulic pump is insufficient.
The present invention is made in view of the above-described problem and an object thereof is to provide a construction machine that can cause each hydraulic actuator to accurately operate according to operation by an operator in combined operation in which a hydraulic fluid delivered from a hydraulic pump is subjected to flow dividing and is supplied to plural hydraulic actuators.
In order to achieve the above-described object, the present invention provides a construction machine including a hydraulic pump, a regulator that adjusts the delivery flow rate of the hydraulic pump, a plurality of hydraulic actuators, a plurality of directional control valves that adjust the flow rate of a hydraulic fluid that is delivered from the hydraulic pump and is distributed to the plurality of hydraulic actuators, and an operation device for operating the plurality of hydraulic actuators. The construction machine includes also a controller configured to decide a target flow rate that is a target value of the inflow flow rate of each of the plurality of hydraulic actuators on the basis of an operation signal inputted from the operation device and control the regulator and the plurality of directional control valves according to the respective target flow rates of the plurality of hydraulic actuators. This construction machine includes velocity sensors that sense the respective operation velocities of the plurality of hydraulic actuators. The controller is configured to calculate the respective inflow flow rates of the plurality of hydraulic actuators on the basis of the respective operation velocities of the plurality of hydraulic actuators sensed by the velocity sensors, determine whether or not combined operation in which two or more hydraulic actuators in the plurality of hydraulic actuators are simultaneously operated is being carried out on the basis of the operation signal inputted from the operation device, and in a case of determining that the combined operation is being carried out, control the regulator in such a manner that the delivery flow rate of the hydraulic pump becomes larger than the total target flow rate of the plurality of hydraulic actuators and control the respective opening amounts of the plurality of directional control valves in such a manner that the difference between the respective target flow rates of the plurality of hydraulic actuators and the respective inflow flow rates of the plurality of hydraulic actuators sensed by the velocity sensors becomes small.
According to the present invention configured as above, when it is determined that the combined operation is being carried out, the delivery flow rate of the hydraulic pump is increased relative to the total target flow rate of the plural hydraulic actuators. In addition, the difference between the respective inflow flow rates and the respective target flow rates of the plural hydraulic actuators is reflected only in control of the respective opening amounts of the plural directional control valves. This can prevent interference between the delivery flow rate control of the hydraulic pump and the opening control of the plural directional control valves with avoidance of the situation in which the delivery flow rate of the hydraulic pump is insufficient. Due to this, the flow rate can be accurately distributed to the plural hydraulic actuators. Therefore, it becomes possible to cause the plural hydraulic actuators to accurately operate according to operation by the operator.
According to the construction machine according to the present invention, it becomes possible to cause each hydraulic actuator to accurately operate according to operation by an operator in combined operation in which a hydraulic fluid of a hydraulic pump is subjected to flow dividing and is supplied to plural hydraulic actuators.
Description will be made below with reference to the drawings by taking a hydraulic excavator as an example as a construction machine according to embodiments of the present invention. In the respective diagrams, equivalent components are given the same numeral and overlapping description is omitted as appropriate.
In
The boom 4, the arm 5, and the bucket 6 operate on a single plane (hereinafter, operation plane). The operation plane is a plane orthogonal to the pivot axes of the boom 4, the arm 5, and the bucket 6 and can be set to pass through the center of the boom 4, the arm 5, and the bucket 6 in the width direction.
In a cab 9 in which an operator rides, an operation lever device (operation device) 9a that outputs an operation signal for operating the hydraulic actuators 2a and 4a to 6a and an operation lever device (operation device) 9b that outputs an operation signal for driving the traveling motors 3a are disposed. The operation lever device 9a is two operation levers that can be inclined forward, rearward, leftward, and rightward and the operation lever device 9b is two operation levers that can be inclined in the front-rear direction. The operation lever devices 9a and 9b include a sensor that electrically senses an operation signal corresponding to the inclination amount of the operation lever (lever operation amount). The lever operation amount sensed by this sensor is outputted to a controller 10 (illustrated in
Operation control of the boom cylinder 4a, the arm cylinder 5a, the bucket cylinder 6a, the swing motor 2a, and the left and right traveling motors 3a is carried out by controlling, by a control valve 8, the direction and the flow rate of a hydraulic operating fluid supplied from a hydraulic pump 7 driven by a prime mover 40 to the respective hydraulic actuators 2a to 6a. Control of the control valve 8 is carried out by a drive signal (pilot pressure) output from a pilot pump 70 to be described later through a solenoid proportional pressure reducing valve to be described later. By controlling the solenoid proportional pressure reducing valve by the controller 10 on the basis of the operation signal from the operation lever devices 9a and 9b, operation of the respective hydraulic actuators 2a to 6a is controlled.
The operation lever devices 9a and 9b may be a hydraulic pilot system different from the above description and may be each configured to supply a pilot pressure according to the operation direction and the operation amount of the operation lever operated by an operator to the control valve 8 as a drive signal. In this case, the configuration may be made in such a manner that the pilot pressure according to the operation amount is sensed by a pressure sensor and the sensed pressure is outputted to the controller 10 as an electrical signal and the respective hydraulic actuators 2a to 6a are driven by the solenoid proportional pressure reducing valve to be described later.
Inertial measurement units 12 to 14 are what measure the angular velocity and the acceleration. The boom inertial measurement unit 12, the arm inertial measurement unit 13, and the bucket inertial measurement unit 14 configure a boom cylinder velocity sensor 12, an arm cylinder velocity sensor 13, and a bucket cylinder velocity sensor 14 that sense the operation velocity of the boom cylinder 4a, the arm cylinder 5a, and the bucket cylinder 6a, respectively, on the basis of the measured angular velocity and acceleration.
The cylinder velocity sensor is not limited to the inertial measurement unit. For example, the configuration may be made in such a manner that a stroke sensor is disposed for each the boom cylinder 4a, the arm cylinder 5a, and the bucket cylinder 6a and the operation velocity of the boom cylinder 4a, the arm cylinder 5a, and the bucket cylinder 6a is computed by carrying out numerical differentiation of the stroke change amount.
The hydraulic actuator control system is composed of the control valve 8 that drives the respective hydraulic actuators 2a to 6a, the hydraulic pump 7 that supplies the hydraulic fluid to the control valve 8, the pilot pump 70 that supplies the pilot pressure that becomes the drive signal of the control valve 8, and the prime mover 40 for driving the hydraulic pump 7. In the present embodiment, a variable displacement type is employed as the hydraulic pump 7, and a solenoid proportional pressure reducing valve 7a for the variable displacement pump operates on the basis of a current command from the controller 10 and thereby the capacity of the hydraulic pump 7 is adjusted and the delivery flow rate of the hydraulic pump 7 is controlled. A configuration may be employed in which a fixed displacement type is employed as the hydraulic pump 7 and the rotation velocity of the prime mover 40 is adjusted by a control command from the controller 10 to control the delivery flow rate of the hydraulic pump 7.
The hydraulic fluid delivered by the hydraulic pump 7 is distributed to the respective hydraulic actuators by a boom directional control valve 8a1, an arm directional control valve 8a3, and a bucket directional control valve 8a5. The boom directional control valve 8a1 servers as an opening (meter-in opening) through which one of a bottom-side fluid chamber 4a1 or a rod-side fluid chamber 4a2 of the boom cylinder 4a communicates with a hydraulic fluid line that leads to the hydraulic pump 7, and serves as an opening (meter-out opening) through which the other communicates with a hydraulic fluid line that leads to a tank 41. Solenoid proportional pressure reducing valves 8a2 for the boom directional control valve operate on the basis of the current command ordered from the controller 10 and thereby the pilot pressure is adjusted, and thus the opening amount when the boom directional control valve 8a1 communicates with the bottom-side fluid chamber 4a1 or the rod-side fluid chamber 4a2 is controlled. When the solenoid proportional pressure reducing valve 8a2a is driven, the hydraulic fluid flows from the bottom-side fluid chamber 4a1 to the rod-side fluid chamber 4a2. On the other hand, when the solenoid proportional pressure reducing valve 8a2b is driven, the hydraulic fluid flows from the rod-side fluid chamber 4a2 to the bottom-side fluid chamber 4a1. The arm directional control valve 8a3 also similarly communicates with a bottom-side fluid chamber 5a1 and a rod-side fluid chamber 5a2 of the arm cylinder 5a and the opening amount thereof is controlled by solenoid proportional pressure reducing valves 8a4 for the arm directional control valve. The bucket directional control valve 8a5 communicates with a bottom-side fluid chamber 6a1 and a rod-side fluid chamber 6a2 of the bucket cylinder 6a and the opening amount thereof is controlled by solenoid proportional pressure reducing valves 8a6 for the bucket directional control valve.
Part of the hydraulic fluid delivered from the hydraulic pump 7 is discharged to the tank 41 by a bleed-off valve 8b1 communicating a hydraulic fluid line to the tank 41. For the bleed-off valve 8b1, a solenoid proportional pressure reducing valve 8b2 for the bleed-off valve operates on the basis of the current command ordered from the controller 10 and thereby the pilot pressure is adjusted, and thus the flow rate of the discharge to the tank 41 is controlled. Instead of installing the bleed-off valve 8b1, a configuration may be employed in which directional control valves of an open center type that allow three-direction control are employed as the directional control valves 8a1, 8a3, and 8a5 and a bleed-off opening is adjusted in conjunction with the meter-in opening and the meter-out opening.
In
The target flow rate deciding section 10a decides target flow rates Qa1, Qa2, and Qa3 of inflow to the respective hydraulic actuators and the target flow rates of the respective hydraulic actuators 4a to 6a are outputted to the boom cylinder meter-in opening control section 10e1, the arm cylinder meter-in opening control section 10e2, and the bucket cylinder meter-in opening control section 10e3.
In the present embodiment, the target flow rates Qa1, Qa2, and Qa3 of inflow to the respective hydraulic actuators 4a to 6a are decided on the basis of the operation amount inputted from the operation lever device 9a. A configuration may be employed in which the target flow rates Qa1, Qa2, and Qa3 are decided on the basis of the posture of the front device 1 of the hydraulic excavator 100 or the relative positional relation between the work equipment 6 of the front device 1 and the target working surface besides the operation amount inputted from the operation lever device 9a.
The combined operation determining section 10b determines whether the present state is the state in which two or more hydraulic actuators are simultaneously operating, i.e. a combined operation state. A determination flag that is a binary signal indicating whether the present state is the combined operation state is outputted to the pump delivery flow rate control section 10c.
In the present embodiment, whether the present state is the combined operation state is determined on the basis of the target flow rates Qa1, Qa2, and Qa3 inputted from the target flow rate deciding section 10a. Whether the present state is the combined operation state may be determined on the basis of the operation amount inputted from the operation lever device 9a.
The pump delivery flow rate control section 10c decides the target delivery flow rate of the hydraulic pump 7 on the basis of a total value Qp of the target flow rates to the respective hydraulic actuators 4a to 6a computed by the target flow rate deciding section 10a and the combined operation determination flag inputted from the combined operation determining section 10b. When it is determined that the combined operation is being carried out, a flow rate obtained by adding an offset flow rate to be described later with
The boom cylinder flow rate estimating section 10d1, the arm cylinder flow rate estimating section 10d2, and the bucket cylinder flow rate estimating section 10d3 compute estimated flow rates Qe1, Qe2, and Qe3 at which inflow to the boom cylinder 4a, the arm cylinder 5a, and the bucket cylinder 6a is estimated to be caused, on the basis of cylinder velocities Ve1, Ve2, and Ve3 sensed by the boom cylinder velocity sensor 12, the arm cylinder velocity sensor 13, and the bucket cylinder velocity sensor 14. In the boom cylinder flow rate estimating section 10d1, the estimated flow rate Qe1 of the boom cylinder 4a is computed from the following expression (1).
[Expression 1]
Q
e1
=S
a1
V
e1 (1)
Here, Sa1 is the sectional area of the boom cylinder 4a. When the hydraulic fluid flows in from the bottom-side fluid chamber 4a1, the sectional area of the bottom side of the boom cylinder 4a is defined as Sa1. When the hydraulic fluid flows in from the rod-side fluid chamber 4a2, the sectional area of the rod side of the boom cylinder 4a is defined as Sa1. Also regarding the arm cylinder flow rate estimating section 10d2 and the bucket cylinder flow rate estimating section 10d3, the estimated flow rates Qe2 and Qe3 are computed by similar calculation with use of expression (1). Thus, detailed description is omitted. The estimated flow rates Qe1, Qe2, and Qe3 are outputted to the boom cylinder meter-in opening control section 10e1, the arm cylinder meter-in opening control section 10e2, and the bucket cylinder meter-in opening control section 10e3, respectively.
The boom cylinder meter-in opening control section 10e1, the arm cylinder meter-in opening control section 10e2, and the bucket cylinder meter-in opening control section 10e3 decide the opening amount of the meter-in valves 8a1, 8a3, and 8a5 in such a manner as to correct the error between the target flow rate and the estimated flow rate, on the basis of the inflow flow rate Qe1 to the boom cylinder estimated by the boom cylinder flow rate estimating section 10d1, the inflow flow rate Qe2 to the arm cylinder estimated by the arm cylinder flow rate estimating section 10d2, the inflow flow rate Qe3 to the bucket cylinder estimated by the bucket cylinder flow rate estimating section 10d3, and the target flow rates Qa1, Qa2, and Qa3 to the respective hydraulic actuators computed by the target flow rate deciding section 10a. Current commands Ia1,ref, Ia2,ref, and Ia3,ref for adjustment to the decided opening amounts are outputted to the solenoid proportional pressure reducing valves 8a2 for the boom directional control valve, the solenoid proportional pressure reducing valves 8a4 for the arm directional control valve, and the solenoid proportional pressure reducing valves 8a6 for the bucket directional control valve.
In the boom cylinder meter-in opening control section 10e1, the current command Ta1,ref to the solenoid proportional pressure reducing valves 8a2 for the boom directional control valve is calculated with the following expressions (2), (3), and (4).
[Expression 2]
Q
a1,new
=Q
a1
+K
1∫(Qa1−Qe1)dt (2)
[Expression 3]
A
a1
=f
1(Qa1,new) (3)
[Expression 4]
I
a1,ref
=g
1(Aa1) (4)
Here, Qa1,new is the target flow rate to the boom cylinder 4a resulting from addition of a correction amount computed on the basis of the estimated flow rate Qe1. Aa1 is the target opening amount of the boom meter-in valve 8a1. KI is the feedback gain of integral control. f1 is a transformation table from the post-correction target flow rate Qa1,new to the target opening amount Aa1. g1 is a transformation table from the target opening amount Aa1 to the current command Ia1,ref. In expression (2), a feed-forward amount to command the target flow rate Qa1 as it is and a feedback amount to correct the error between the target flow rate Qa1 and the estimated flow rate Qe1 are added to each other. By correcting the error between the target flow rate Qa1 and the estimated flow rate Qe1, achievement of robustness against variation in dynamic characteristics of the hydraulic system due to the influence of the fluid temperature and so forth is intended. Furthermore, by integrating the error between the target flow rate Qa1 and the estimated flow rate Qe1 to make the correction amount, a stationary flow rate error that occurs due to an error in the flow rate coefficient and flow rate loss of the hydraulic fluid is eliminated.
Also in the arm cylinder meter-in opening control section 10e2 and the bucket cylinder meter-in opening control section 10e3, the current commands Ia2,ref and Ia3,ref are computed by similar calculation with use of expressions (2) to (4). Thus, detailed description is omitted.
The bleed-off opening control section 10f calculates and outputs a current command Ib,ref to the solenoid proportional pressure reducing valve 8b2 for bleed-off. As one example, the bleed-off valve 8b1 in the present embodiment is controlled to be always in the state in which a constant opening is opened irrespective of the operation amount of the operation levers 9a and 9b. A configuration may be employed in which the opening amount of the bleed-off valve 8b1 is adjusted to be subordinate to the opening amount of the directional control valves 8a1, 8a3, and 8a5.
In the pump delivery flow rate control section 10c, on the basis of the determination flag inputted from the combined operation determining section 10b, a constant flow rate Qconst is selected by a selector SLT1 when the combined operation is being carried out and a zero flow rate Q0=0 is selected by the selector SLT1 when the combined operation is not being carried out. The selected flow rate is transmitted as an offset command Qoffset and is added to a target flow rate Qp to become a post-correction target flow rate Qp,new. Finally, transformation is carried out from the post-correction target flow rate Qp,new to the current command Ip,ref by a transformation table TBL and the current command Ip,ref is outputted to the solenoid proportional pressure reducing valve 7a for the variable displacement pump.
By determining that the combined operation is being carried out and increasing the delivery flow rate of the hydraulic pump 7 with respect to the target flow rate Qp, the situation in which the delivery flow rate of the hydraulic pump 7 is insufficient with respect to the target flow rate Qp can be surely avoided.
In the bleed-off opening control section 10f, a constant opening amount Aconst set in advance is given as a target opening amount Ab and transformation is carried out from the target opening amount Ab to the current command Ib,ref by a transformation table TBL2. The current command Ib,ref is outputted to the solenoid proportional pressure reducing valve 8b2 for bleed-off.
By always opening the bleed-off valve 8b1 by the constant opening amount Aconst, the delivery flow rate of the hydraulic pump 7 as the part that becomes surplus due to the offset command Qoffset can be discharged from the bleed-off valve 8b1 and the situation in which the surplus hydraulic fluid flows in to the hydraulic actuators 4a to 6a can be avoided.
In
In
In the present embodiment, the construction machine 100 includes the hydraulic pump 7, the regulator 7a that adjusts the delivery flow rate of the hydraulic pump 7, the plural hydraulic actuators 4a, 5a, and 6a, the plural directional control valves 8a1, 8a3, and 8a5 that adjust the flow rate of the hydraulic fluid that is delivered from the hydraulic pump 7 and is distributed to the plural hydraulic actuators 4a, 5a, and 6a, and the operation device 9a for operating the plural hydraulic actuators 4a, 5a, and 6a. The construction machine 100 includes also the controller 10 that decides the target flow rate that is the target value of the inflow flow rate of each of the plural hydraulic actuators 4a, 5a, and 6a on the basis of an operation signal inputted from the operation device 9a and controls the regulator 7a and the plural directional control valves 8a1, 8a3, and 8a5 according to the respective target flow rates of the plural hydraulic actuators 4a, 5a, and 6a. This construction machine 100 includes the velocity sensors 12 to 14 that sense the respective operation velocities of the plural hydraulic actuators 4a, 5a, and 6a. The controller 10 calculates the respective inflow flow rates of the plural hydraulic actuators 4a, 5a, and 6a on the basis of the respective operation velocities of the plural hydraulic actuators 4a, 5a, and 6a sensed by the velocity sensors 12 to 14. The controller 10 determines whether or not the combined operation in which two or more hydraulic actuators in the plural hydraulic actuators 4a, 5a, and 6a are simultaneously operated is being carried out on the basis of the operation signal inputted from the operation device 9a. When determining that the combined operation is being carried out, the controller 10 controls the regulator 7a in such a manner that the delivery flow rate of the hydraulic pump 7 becomes larger than the total target flow rate of the plural hydraulic actuators and controls the respective opening amounts of the plural directional control valves 8a1, 8a3, and 8a5 in such a manner that the difference between the respective target flow rates of the plural hydraulic actuators 4a, 5a, and 6a and the respective inflow flow rates of the plural hydraulic actuators 4a, 5a, and 6a sensed by the velocity sensors 12 to 14 becomes small.
According to the present embodiment configured as above, when it is determined that the combined operation is being carried out, the delivery flow rate of the hydraulic pump 7 is increased relative to the total target flow rate of the plural hydraulic actuators 4a, 5a, and 6a. In addition, the difference between the respective inflow flow rates and the respective target flow rates of the plural hydraulic actuators 4a, 5a, and 6a is reflected only in control of the respective opening amounts of the plural directional control valves 8a1, 8a3, and 8a5. This can prevent interference between the delivery flow rate control of the hydraulic pump 7 and the opening control of the plural directional control valves 8a1, 8a3, and 8a5 with avoidance of the situation in which the delivery flow rate of the hydraulic pump 7 is insufficient. Due to this, the flow rate can be accurately distributed to the plural hydraulic actuators 4a, 5a, and 6a. Therefore, it becomes possible to cause the plural hydraulic actuators 4a, 5a, and 6a to accurately operate according to operation by the operator.
A hydraulic excavator according to a second embodiment of the present invention will be described with focus on a difference from the first embodiment.
In the present embodiment, the bleed-off valve 8b1 is driven independently of the directional control valves 8a1, 8a3, and 8a5. The bleed-off opening control section 10f illustrated in
In the bleed-off opening control section 10f, on the basis of the determination flag inputted from the combined operation determining section 10b, the constant opening Aconst is selected by a selector SLT2 when the combined operation is being carried out and zero opening A0=0 is selected by the selector SLT2 when the combined operation is not being carried out. The selected opening amount is transmitted as the target opening Ab of the bleed-off valve 8b1 and transformation is carried out from the target opening Ab to the current command Ib,ref by the transformation table TBL2. The current command Ib,ref is outputted to the solenoid proportional pressure reducing valve 8b2 for the bleed-off valve.
The construction machine 100 according to the present embodiment includes the bleed-off valve 8b1 for discharging the surplus part of the hydraulic fluid delivered by the hydraulic pump 7 in such a manner that the bleed-off valve 8b1 is driven independently of the plural directional control valves 8a1, 8a3, and 8a5. The controller 10 carries out control to open the bleed-off valve 8b1 when determining that the combined operation is being carried out and close the bleed-off valve 8b1 when determining that the combined operation is not being carried out.
According to the present embodiment configured as above, the following effect is obtained in addition to the same effects as the first embodiment.
By fully closing the bleed-off valve 8b1 when the combined operation is not being carried out, wasteful flow rate discharge from the bleed-off valve 8b1 to the tank 41 can be suppressed while the flow rate error at the time of the combined operation is corrected by the boom cylinder meter-in opening control section 10e1, the arm cylinder meter-in opening control section 10e2, and the bucket cylinder meter-in opening control section 10e3. This makes it possible to achieve both the control accuracy of the hydraulic actuator and the energy saving performance.
A hydraulic excavator according to a third embodiment of the present invention will be described with focus on a difference from the first embodiment.
In the hydraulic actuator control system illustrated in
The boom cylinder flow rate sensor 71, the arm cylinder flow rate sensor 72, and the bucket cylinder flow rate sensor 73 output the computed estimated flow rates Qe1, Qe2, and Qe3 to the boom cylinder meter-in opening control section 10e1, the arm cylinder meter-in opening control section 10e2, and the bucket cylinder meter-in opening control section 10e3.
The construction machine 100 according to the present embodiment includes the plural flow rate sensors 71 to 73 each disposed upstream of the plural directional control valves 8a1, 8a3, and 8a5 instead of the velocity sensors 12 to 14.
According to the present embodiment configured as above, the following effect is obtained in addition to the same effects as the first embodiment.
By directly sensing the inflow flow rates to the respective hydraulic actuators 4a to 6a by the boom cylinder flow rate sensor 71, the arm cylinder flow rate sensor 72, and the bucket cylinder flow rate sensor 73, the estimation error of the estimated flow rates Qe1, Qe2, and Qe3 due to the influence of friction and vibration at the time of hydraulic actuator operation can be removed and the estimated flow rates Qe1, Qe2, and Qe3 can be computed more accurately. In addition, by controlling each opening amount of the directional control valves 8a1, 8a3, and 8a5 by using the more accurate estimated flow rates Qe1, Qe2, and Qe3, the inflow flow rates to the hydraulic actuators 4a, 5a, and 6a can be distributed more accurately.
A hydraulic excavator according to a fourth embodiment of the present invention will be described with focus on a difference from the first embodiment.
In the hydraulic actuator control system illustrated in
To the boom cylinder meter-in opening control section 10e1, a pump delivery pressure Pd sensed by the pump delivery pressure sensor 51 and a boom load pressure Pa1 sensed by the boom load pressure sensors 52 and 55 are input in addition to the target flow rate Qa1 computed by the target flow rate deciding section 10a and the estimated flow rate Qe1 estimated by a boom cylinder flow rate estimating section 10f1. The boom cylinder meter-in opening control section 10e1 transforms, by the following expression (5), the post-correction target flow rate Qa1,new computed by expression (2) to the target opening amount Aa1.
Here, k is a positive constant value defined with the influence of the flow rate coefficient, the density of the hydraulic fluid, and so forth being also taken into consideration. As shown in the denominator of the right side of expression (5), the target opening amount Aa1 of the boom meter-in valve 8a1 is decided in consideration of the differential pressure between the pressure on the upstream side of the boom meter-in valve 8a1 (pump delivery pressure Pd) and the pressure on the downstream side (boom load pressure Pa1). This can compensate change in the passing flow rate of the boom meter-in valve 8a1 due to the influence of the differential pressure. The current command Ia1,ref to the solenoid proportional pressure reducing valves 8a2 for the boom directional control valve is computed by using expressions (2), (4), and (5).
The arm cylinder meter-in opening control section 10e2 uses the target flow rate Qa2, the estimated flow rate Qe2, the pump delivery pressure Pd, and the arm load pressure Pa2 to compute the current command Ia2, ref from expressions (2), (4), and (5). The bucket cylinder meter-in opening control section 10e3 uses the target flow rate Qa3, the estimated flow rate Qe3, the pump delivery pressure Pd, and the bucket load pressure Pa3 to compute the current command Ia3,ref from expressions (2), (4), and (5).
The construction machine 100 according to the present embodiment further includes the first pressure sensor 51 disposed on the respective hydraulic fluid lines that couple the hydraulic pump 7 to the plural directional control valves 8a1, 8a3, and 8a5 and the second pressure sensors 52 to 57 disposed on the respective hydraulic fluid lines that couple the plural directional control valves 8a1, 8a3, and 8a5 to the plural hydraulic actuators 4a, 5a, and 6a. The controller 10 controls the plural directional control valves 8a1, 8a3, and 8a5 according to the differential pressures across the plural directional control valves 8a1, 8a3, and 8a5 sensed by the first pressure sensor 51 and the second pressure sensors 52 to 57.
According to the present embodiment configured as above, the following effect is obtained in addition to the same effects as the first embodiment.
By deciding the target opening amount Aa1 of the meter-in valves 8a1, 8a3, and 8a5 in consideration of the differential pressure between the pressure on the upstream side of the meter-in valves 8a1, 8a3, and 8a5 (pump delivery pressure Pd) and the pressure on the downstream side (load pressure Pa1), change in the passing flow rate of the meter-in valve due to the influence of the differential pressure can be compensated. This can improve the velocity responsiveness of the hydraulic actuators 4a to 6a with respect to variation in the load pressure.
A hydraulic excavator according to a fifth embodiment of the present invention will be described with focus on a difference from the fourth embodiment.
The bleed-off opening control section 10f computes the current command Ib,ref to the solenoid proportional pressure reducing valve 8b2 for the bleed-off valve on the basis of the pump delivery pressure Pd inputted from the pump delivery pressure sensor 51 in addition to the determination flag inputted from the combined operation determining section 10b.
When a load is applied to the hydraulic actuator, the pump delivery pressure Pd increases and the discharge flow rate of discharge from the bleed-off valve 8b1 to the tank 41 increases. It is anticipated that, when the discharge flow rate increases, the flow rate of inflow to the hydraulic actuator decreases and the error between the target flow rate and the estimated flow rate increases.
In order to prevent the increase in the flow rate error when a load is applied to the hydraulic actuator, for example, the constant opening Aconst shown in
Here, Qb,const is a target constant discharge flow rate of discharge from the bleed-off valve 8b1. The pump delivery pressure Pd sensed by the pump delivery pressure sensor 51 is used as input and the constant opening Aconst is computed by TBL3 to carry out calculation of expression (6).
By TBL3, the opening amount of the bleed-off valve 8b1 is adjusted to carry out discharge at the constant flow rate Qb,const irrespective of variation in the pump delivery pressure Pd.
The construction machine according to the present embodiment further includes the pressure sensor 51 disposed downstream of the hydraulic pump 7 and the controller 10 corrects the opening amount of the bleed-off valve 8b1 according to the pressure on the downstream side of the hydraulic pump 7 sensed by the pressure sensor 51.
According to the present embodiment configured as above, the following effect is obtained in addition to the same effects as the fourth embodiment.
By carrying out control in such a direction that the opening of the bleed-off valve 8b1 is closed in response to increase in the load on the hydraulic actuators 4a, 5a, and 6a and reducing the discharge flow rate to the tank 41, decrease in the flow rate of inflow to the hydraulic actuators 4a, 5a, and 6a can be prevented.
A hydraulic excavator according to a sixth embodiment of the present invention will be described with focus on a difference from the first embodiment.
In the hydraulic actuator control system illustrated in
The construction machine 100 according to the present embodiment includes each of the pressure compensating valves 61 to 63 for keeping the pressure difference between the upstream side and the downstream side of the plural directional control valves 8a1, 8a3, and 8a5 constant on the respective upstream sides of the plural directional control valves 8a1, 8a3, and 8a5.
According to the present embodiment configured as above, the following effect is obtained in addition to the same effects as the first embodiment.
The pressure compensating valves 61 to 63 cause the differential pressures across the meter-in valves 8a1, 8a3, and 8a5 to be adjusted to be constant. Due to this, without installing the pressure sensors 51 to 57 illustrated in
Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and various modification examples are included therein. For example, the above-described embodiments are what are described in detail for explaining the present invention in an easy-to-understand manner and are not necessarily limited to what include all configurations described. Furthermore, it is also possible to add part of a configuration of a certain embodiment to a configuration of another embodiment, and it is also possible to delete part of a configuration of a certain embodiment or replace the part by part of another embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-025233 | Feb 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/049037 | 12/13/2019 | WO | 00 |
