EP4667665A1

EP4667665A1 - Hydraulic control system for construction machine

Info

Publication number: EP4667665A1
Application number: EP24778672.6A
Authority: EP
Inventors: Shouta ISHIDA; Ryouhei FUKUCHI; Mitsuhiko Kanehama
Original assignee: Hitachi Construction Machinery Co Ltd
Current assignee: Hitachi Construction Machinery Co Ltd
Priority date: 2023-03-31
Filing date: 2024-02-02
Publication date: 2025-12-24
Also published as: JP2024146191A; JP7496910B1; WO2024202526A1; CN120882938A; KR20250148671A

Abstract

The present invention provides a hydraulic control system for construction machine that prevents false detection of travel jerky occurrence during the operation of travel control pedals and achieves good travel operability. Therefore, the controller calculates the target operation pressure according to the operation amount of the travel control lever and travel control pedal based on the operation signal of the travel operation device. Then, the controller inputs the control operation pressure generated by the travel electromagnetic proportional control valve detected by the pressure sensor, calculates the pressure difference between the target operation pressure and the control operation pressure, and determines whether travel jerky has occurred based on the change in the pressure difference.

Description

Technical Field

The present invention relates to a hydraulic control system for construction machine, particularly to a hydraulic control system for construction machine that can suppress the occurrence of jerky phenomena during travel.

Background Art

In construction machine such as crawler cranes and hydraulic excavators, during travel when the operator operates the travel operation device, the vehicle body may vibrate due to the influence of the road surface, causing travel jerky. Travel jerky refers to the phenomenon where, when the vehicle body vibrates due to the influence of the road surface, the operator's sway causes the control lever or control pedal to sway in a phase different from the vehicle body's vibration, resulting in unintended acceleration or deceleration of the vehicle body.
Conventionally, various methods have been proposed to effectively suppress the occurrence of such travel jerky, with Patent Document 1 being one example.
In Patent Document 1, an inertial sensor is used to detect the vibration of the upper swing body or the seat in the operating room, and it is determined whether the increase or decrease in acceleration in the longitudinal direction of the upper swing body or seat has been repeated a predetermined number of times. Alternatively, the travel command value of the travel operation device is detected by an operation pressure sensor, and it is determined whether the increase or decrease in the travel command value has been repeated a predetermined number of times. Then, if the determination result meets the predetermined conditions and it is determined that the travel operation is unstable (travel jerky is occurring), it is proposed to correct the travel command value to suppress the fluctuation of the travel command value.

Prior Art Documents

Patent Documents

Patent Document 1: WO2021/025035

Summary of the Invention

Problems to be Solved by the Invention

Patent Document 1 detects the occurrence of travel jerky by using an inertial sensor to detect the vibration of the upper swing body or seat and the travel command value, and determining whether the increase or decrease in vibration acceleration of the upper swing body or seat and the increase or decrease in travel command value have been repeated a predetermined number of times or more. However, if the occurrence of travel jerky is determined based on the increase or decrease in vibration acceleration of the upper swing body or seat and the increase or decrease in travel command value, there is a possibility of false detection of travel jerky occurrence.
More specifically, the travel operation device of construction machine has left and right travel levers and left and right travel pedals located at the base end of the travel levers, which operate in conjunction with the travel levers. Therefore, the operation mode of travel includes cases where the operator manually operates the travel lever and cases where the operator foot-operates the travel pedal.
When the vehicle body vibrates and sways during travel, the travel lever and travel pedal attached to the floor of the vehicle body sway, and the operator's body also sways. At this time, the operator's upper body tends to sway significantly in response to the vehicle body's sway, but the operator's lower body does not sway as much because it is held by the seat in the operator's seat. Therefore, when the operator manually operates the travel lever, the sway is transmitted to the travel lever, causing the travel lever to sway significantly, and travel jerky is likely to occur due to the difference between the vehicle body's sway and the travel lever's sway. On the other hand, when the operator foot-operates the travel pedal, the sway of the travel pedal is small, and the difference between the vehicle body's sway and the travel pedal's sway is small, making travel jerky less likely to occur. As a result, by using a travel jerky occurrence detection system that detects the increase or decrease in vibration acceleration of the upper swing body or seat and the increase or decrease in travel command value, there is a possibility of false detection of travel jerky occurrence even when the travel pedal is foot-operated and travel jerky has not occurred.
Here, when the occurrence of driving jerky is detected, fluctuation suppression control of the operation signal (command value) is executed using signal smoothing means such as a low-pass filter. However, if fluctuation suppression control is executed when the occurrence of travel jerky is falsely detected, transmission delay of the command value occurs due to the signal smoothing means, and the responsiveness of the travel operation decreases. Therefore, when the operator operates the travel pedal, the movement may differ from the operator's intended operation, potentially reducing travel operability.
The object of the present invention is to provide a hydraulic control system for construction machine that can prevent false detection of travel jerky occurrence during travel control pedal operation and achieve good travel operability.

Means for Solving the Problems

To achieve the above object, the hydraulic control system of the present invention includes multiple actuators driven by pressure oil discharged from a hydraulic pump, multiple switching control valves that control the flow of pressure oil discharged from the hydraulic pump and supplied to the travel motor, and a travel control lever and a travel control pedal located adjacent to the base end of the travel control lever. Additionally, the hydraulic control system includes multiple operation devices that generate operation signals corresponding to the operation amount of the travel control lever and travel control pedal, a controller that calculates a target operation pressure based on the operation signal of the travel operation device, generates command current corresponding to the target operation pressure, and corrects the target operation pressure to limit the change rate of the target operation pressure when it is determined that travel jerky has occurred, and a travel electromagnetic proportional control valve that generates control operation pressure corresponding to the command current and operates the travel switching control valve. Furthermore, the hydraulic control system includes a pressure sensor that detects the control operation pressure generated by the travel electromagnetic proportional control valve. The controller calculates the target operation pressure corresponding to the operation amount of the travel control lever and travel control pedal based on the operation signal of the travel operation device. Additionally, the controller inputs the control operation pressure detected by the pressure sensor, calculates the pressure difference between the target operation pressure and the control operation pressure, and determines whether travel jerky has occurred based on the change in the pressure difference.
Thus, in the present invention, unlike Patent Document 1, the occurrence of travel jerky is determined based on the change in the pressure difference between the target operation pressure and control operation pressure, which are parameters directly related to the sway (vibration) of the travel control pedal rather than the vibration of the vehicle body. Therefore, the present invention can accurately estimate the sway of the travel control pedal, prevent false detection of travel jerky occurrence during travel control pedal operation, and achieve good travel operability.

Advantages of the Invention

According to the present invention, false detection of travel jerky occurrence during travel pedal operation can be prevented, and good travel operability can be achieved.

Brief Description of the Drawings

[Fig. 1] A diagram showing the appearance of a hydraulic excavator, which is an example of construction machine according to the present invention.
[Fig. 2] A diagram showing the operating room inside the cabin viewed from the operator's seat side.
[Fig. 3] A diagram showing the hydraulic drive device of the hydraulic control system according to the first embodiment of the present invention.
[Fig. 4] A diagram showing the controller of the hydraulic control system.
[Fig. 5] A diagram showing the change in target operation pressure and control operation pressure during the occurrence of travel jerky.
[Fig. 6] A functional block diagram showing the processing content of the controller.
[Fig. 7] A diagram showing the relationship between the operation signal and operation amount for calculating the operation amount from the operation signal.
[Fig. 8] A diagram showing the relationship between the operation amount and target operation pressure for calculating the target operation pressure from the operation amount.
[Fig. 9] A flowchart showing the overall flow of controller processing.
[Fig. 10A] A flowchart showing the details of the command current generation processing of the electromagnetic proportional control valve in steps S110, S130, S150, S170 of the flowchart in Fig. 9.
[Fig. 10B] A flowchart showing the details of the command current generation processing of the electromagnetic proportional control valve in steps S110, S130, S150, S170 of the flowchart in Fig. 9.
[Fig. 10C] A flowchart showing the details of the command current generation processing of the electromagnetic proportional control valve in steps S110, S130, S150, S170 of the flowchart in Fig. 9.
[Fig. 11] A diagram showing the basic effects obtained by the travel control of this embodiment. The left side of the diagram shows the change in target operation pressure and control operation pressure before applying the control of this embodiment, and the right side shows the change in target operation pressure and control operation pressure after applying the control of this embodiment.
[Fig. 12] A functional block diagram showing the processing content of the controller in the second embodiment of the present invention.
[Fig. 13] A functional block diagram showing the details of the state determination unit of the controller shown in Fig. 12.
[Fig. 14] A flowchart showing an example of the processing of the pressure difference threshold determination unit shown in Fig. 13.
[Fig. 15] A diagram showing the relationship between the boom angle and the first threshold coefficient K1 used in the processing of the pressure difference threshold determination unit.
[Fig. 16] A diagram showing in tabular form the relationship between the second threshold coefficient when the travel direction is forward and the second threshold coefficient when the travel direction is backward, used in the processing of the pressure difference threshold determination unit.
[Fig. 17] A diagram showing the relationship between the operation torque of the control pedal and the basic threshold when determining the basic threshold based on the operation torque of the control pedal.
[Fig. 18] A functional block diagram showing the details of the state determination unit of the controller in the third embodiment of the present invention.
[Fig. 19] A diagram showing the relationship between the difference in target operation pressure and control operation pressure used to estimate the magnitude of vibration of the control pedal and the magnitude of vibration of the control pedal.
[Fig. 20] A diagram showing the relationship between the magnitude of vibration of the control pedal and the filter time constant τ.

Modes for Carrying the Invention

The embodiments of the present invention will be described below with reference to the drawings.

(Hydraulic Excavator)

Figure 1 is a diagram showing the appearance of a hydraulic excavator, which is an example of construction machine according to the present invention.
In Figure 1, the hydraulic excavator is schematically composed of a crawler-type lower travel body 1, an upper swing body 2 rotatably attached on the lower travel body 1, and a front working machine 3 that is pivotally attached to the front of the upper swing body 2 in the vertical direction to perform operations such as excavation.
The lower travel body 1 includes left and right travel motors 1a, 1b and left and right crawlers 1c, 1d, and travels by driving the left and right crawlers 1c, 1d with the travel motors 1a, 1b.
The upper swing body 2 is equipped with a cabin 4, a prime mover 5, a hydraulic pump 6, and a swing motor 2a, among others, and the upper swing body 2 is swung to the right or left direction relative to the lower travel body 1 by the swing motor 2a.
The front working machine 3 is composed of a boom 3a, an arm 3b, and a bucket 3c, where the boom 3a is moved up and down by a boom cylinder 3d, the arm 3b is operated in the dump direction (opening direction) or the crowd direction (scooping direction) by an arm cylinder 3e, and the bucket 3c is operated in the dump direction or the crowd direction by a bucket cylinder 3f.

(Operator Cab)

Figure 2 is a view of the operator cab inside the cabin 4 from the operator's seat side.
In Figure 2, an operating room 4a is formed inside the cabin 4, and within the operator cab 4a, there is a operator's seat 51 where the operator sits, and left and right control levers 52a, 53a for instructing the operation of the front working machine 3 and the upper swing body 2. Additionally, inside the cabin 4, there are operation devices 52, 53 that generate operation signals according to the operation amount of the control levers 52a, 53a, and left and right control levers 54a, 55a and left and right control pedals 54b, 55b for instructing the operation of the left and right crawlers 1c, 1d of the lower travel body 1. Furthermore, inside the cabin 4, there are lever/pedal type operation devices (hereinafter sometimes referred to as travel operation devices) 54, 55 that generate operation signals according to the operation amount of the control levers 54a, 55a and control pedals 54b, 55b. The left and right control pedals (hereinafter sometimes referred to as travel control pedals or travel pedals) 54b, 55b are positioned adjacent to the base end parts of the left and right control levers (hereinafter sometimes referred to as travel control levers or travel levers) 54a, 55a, respectively.
Additionally, on the side of the operator cab 4a where the entrance and exit are located (left side from the perspective of the operator seated in the operator's seat 17), there is a gate lock lever 8 that is pivotally operated between an unlock position (a lowered position that obstructs the operator's entry and exit) and a lock position (a raised position that allows the operator's entry and exit). At the base end part of the gate lock lever 8, there is a gate lock switch 8a that is in a closed state when the gate lock lever 8 is in the unlock position (lowered position) and in an open state when in the lock position (raised position). The gate lock switch 8a is electrically connected to the gate lock valve 48 of the hydraulic drive device (see Figure 2), and when the gate lock lever 8 is in the lock position, the gate lock valve 48 is in the OFF position, rendering the operation of the control levers 52a, 53a and the travel control levers 54a, 55a and travel control pedals 54b, 55b invalid. When the gate lock lever 8 is switched to the unlock position, the gate lock valve 48 switches to the ON position, enabling the operation of the control levers 52a, 53a and the travel control levers 54a, 55a and travel control pedals 54b, 55b.
Additionally, on the right side as viewed from the operator's seat 51, there is a monitor 58 used for visibility assistance, equipped with an input section 58a for setting thresholds related to control and other vehicle body settings.

(Operation Device)

The operator sits in the operator's seat 51 and operates the control lever 52a of the operation device 52 with the left hand and the control lever 53a of the operation device 53 with the right hand. The operation devices 52, 53 can each be operated in any direction based on the cross directions of left, right, up, and down from the neutral position, and one control lever 52a, 53a can operate two actuators. The operation of the control lever 52a in the right direction R and left direction L instructs the arm cloud and arm dump operations of the arm cylinder 3e, and the operation of the control lever 52a in the forward direction F and rearward direction R instructs the right and left swing operations of the swing motor 2a. The operation of the control lever 53a in the forward direction F and rearward direction R instructs the boom lowering and boom raising operations of the boom cylinder 3d, and the operation of the control lever 53a in the right direction R and left direction L instructs the bucket dump and bucket crowd operations of the bucket cylinder 3f.
Additionally, the operator operates the control lever 54a of the travel operation device 54 with the left hand, the control lever 55a of the travel operation device 55 with the right hand, the control pedal 54b of the travel operation device 54 with the left foot, and the control pedal 55b of the travel operation device 55 with the right foot. The travel control levers 54a, 55a can each be operated in the forward direction F and rearward direction R from the neutral position, and the operation of the travel control lever 54a in the forward direction F and rearward direction R instructs the forward and reverse operations of the left travel motor 1a, while the operation of the travel control lever 55a in the forward direction F and rearward direction R instructs the forward and reverse operations of the right travel motor 1b.
The travel control pedals 54b, 55b can each be tilted in the forward and rearward directions from the neutral position, and the pedal operation of the travel control pedal 54b in the forward direction F and rearward direction R instructs the forward and reverse operations of the left travel motor 1a, similar to the operation of the travel control lever 54a, while the pedal operation of the travel control pedal 55b in the forward direction F and rearward direction R instructs the forward and reverse operations of the right travel motor 1b, similar to the operation of the travel control lever 55a.
Note that in this specification, the forward, rearward, right, and left directions refer to the forward, rearward, right, and left directions of the upper swing body 102, which is the vehicle body.
In this embodiment, the operation devices 52, 53 and the operation devices 54, 55 are electric operation devices, each equipped with signal generation units 52c, 53c, 54c, 55c (see Figure 2) that generate electrical signals as operation signals. Additionally, the control lever 54a and control pedal 54b of the travel operation device 54 each activate the same signal generation unit 54c to generate electrical signals, and similarly, the control lever 55a and control pedal 55b of the travel operation device 55 each activate the same signal generation unit 55c to generate electrical signals.
The operation devices 52, 53 may also be hydraulic pilot types that generate operation pilot pressure as operation signals.

(Hydraulic Control System)

Figure 3 is a diagram showing the hydraulic drive device of the hydraulic control system according to the first embodiment of the present invention, and Figure 4 is a diagram showing the controller of the hydraulic control system. In Figure 4, the configuration of the aforementioned operation devices 52, 53 and operation devices 54, 55 is shown schematically.
In Figure 3, the hydraulic drive device includes a prime mover 5 (e.g., a diesel engine), a hydraulic pump 6 driven by this prime mover 5, and the aforementioned left and right travel motors 1a, 1b driven by the pressure oil discharged from the hydraulic pump 6, among other actuators 1a, 1b, 2a, 3d, 3e, 3f. Additionally, the hydraulic drive device includes a control valve 19 with multiple switching control valves 13, 14, 15, 16, 17, 18, including travel switching control valves 13, 14 that control the flow (flow rate and direction) of pressure oil discharged from the hydraulic pump 6 and supplied to the travel motors 1a, 1b, and a pilot pump 47 that discharges pressure oil held at a constant pressure by a pilot relief valve 49 to generate pilot primary pressure. Furthermore, the hydraulic drive device includes multiple electromagnetic proportional control valves 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, including travel electromagnetic proportional control valves 20, 21, 22, 23 that generate control pressure (hereinafter sometimes referred to as control operation pressure) as pilot secondary pressure according to command current, and operate the travel switching control valves 13, 14, and the aforementioned gate lock valve 48 that selects whether to guide the pilot primary pressure generated by the pilot pump 47 to the electromagnetic proportional control valves 20 to 31.
The control operation pressure generated by the electromagnetic proportional control valves 20 to 31 is directed to the corresponding pair of pressure receiving sections of the switching control valves 13 to 18. The switching control valves 13 to 18 operate based on this control operation pressure, and pressure oil with a flow rate corresponding to the control operation pressure is supplied to multiple actuators 1a to 3f.
The command current to the electromagnetic proportional control valves 20 to 31 that generate the control operation pressure is calculated by the controller 34 shown in Figure 4 based on the operation signals (electrical signals) from the operation devices 52, 53 and operation devices 54, 55. Then, by switching the switching control valves 13 to 18 with the control operation pressure, multiple actuators 1a to 3f corresponding to the operation signals are driven.
If the operation devices 52, 53 are hydraulic pilot types that generate operation pilot pressure as operation signals, the electromagnetic proportional control valves 24 to 31 related to the operation devices 52, 53 can be eliminated, and the operation pilot pressure can be directly guided to the pressure receiving parts of the switching control valves 16 to 18 to switch the switching control valves 16 to 18.
Moreover, the hydraulic control system according to this embodiment includes a controller 34 as shown in FIG. 4, and pressure sensors 35, 36, 37, and 38 that detect the control operation pressure generated by the travel electromagnetic proportional control valves 20 to 23. Additionally, the controller 34 calculates the target operation pressure corresponding to the operation amount based on the operation signals (electrical signals) from the operation devices 52, 53 and the travel operation devices 54, 55, and generates a command current according to the target operation pressure. Then, if the controller determines that travel jerky has occurred, it limits the rate of change of the target operation pressure by correcting the target operation pressure of the travel operation devices 54, 55.
In FIG. 4, the operation devices 52, 53 and the operation devices 54, 55 are provided with signal generating units 52c, 53c, 54c, 55c (see FIG. 2) that generate electric signals as operation signals, as described above. Moreover, the control pedals 54b, 55b of the travel operation devices 54, 55 are positioned at the base ends of the control levers 54a, 55a, respectively, and operate in conjunction with the control levers 54a, 55a.

(Detection Principle of Travel Jerky)

The principle of detecting travel jerky according to the present invention will be explained.
It is assumed that when decelerating during off-road driving by operating the travel control pedals 54b, 55b, travel jerky occurs. Travel jerky refers to the phenomenon where, during travel operation by the operator using the travel operation devices 54, 55, the vehicle body (upper swing body 2) vibrates due to the influence of the road surface, causing the control levers 54a, 55a or control pedals 54b, 55b to oscillate in a phase different from the vehicle body's vibration due to the operator's sway, resulting in unintended acceleration or deceleration by the operator.
FIG. 5 is a graph showing the changes in the target control pressure (pressure generated by the electromagnetic proportional control valves 20 to 23 operating by command current) and the control operation pressure when such a travel jerky occurs. Moreover, the controller 34 calculates the target operation pressure according to the operation amount based on the operation signals (electric signals) from the operation devices 52, 53 and the travel operation devices 54, 55, generates a command current corresponding to the target operation pressure, and limits the rate of change of the target operation pressure by correcting the target operation pressure of the travel operation devices 54, 55 when it is determined that a travel jerky has occurred. In the figure, the dotted line indicates the target operation pressure, and the solid line indicates the control operation pressure.
There is a delay in tracking performance caused by the delay in the operation of electromagnetic proportional control valves 20 to 23 between the time when controller 34 calculates the target operation pressure based on the operating signals from the operation of travel levers 54a, 55a or travel pedals 54b, 55b and the time when the electromagnetic proportional control valves 20 to 23 operate based on the command current to generate the control operation pressure, and as shown by the dotted and solid lines in Figure 5, a pressure difference occurs between the target operation pressure and the control operation pressure.
In FIG. 5, time t1 is the point in the process where the target operation pressure decreases during deceleration, and the pressure difference becomes smaller than the preset threshold value "-X" (the absolute value of the pressure difference becomes larger than the threshold value "X"). Also, time t2 is the point at which the operation amount turns from a decrease to an increase, and during the process of increasing the target operation pressure, the pressure difference becomes greater than the preset threshold value "X". In other words, time t2 is the point at which the switching between the travel state where the pressure difference is greater than the threshold value "X" and the travel state where the pressure difference is smaller than the threshold value "-X" occurs. The same applies to times t3 and t4.
In this specification, the threshold value "X" may be referred to as the first threshold value, and the threshold value "-X" may be referred to as the second threshold value. Also, the travel state where the pressure difference becomes greater than the first threshold value "X" may be referred to as "state 1" or "first travel state," and the travel state where the pressure difference becomes smaller than the second threshold value "-X" may be referred to as "state 2" or "second travel state".
The present invention focuses on the change in pressure difference during the occurrence of a travel jerky as shown in FIG. 5, and determines whether a travel jerky has occurred.
Here, FIG. 5 was explained as the occurrence of a travel jerky when the travel pedals 54b, 55b are operated, but a pressure difference similarly occurs when the travel levers 54a, 55a are operated, so the occurrence of a travel jerky can also be detected. However, even if the vibration of the vehicle body is the same, the sway of the travel pedals 54b, 55b operated by the operator's feet is smaller than the sway of the travel levers 54a, 55a operated by the operator's hands. For this reason, as in the conventional method, when the occurrence of a travel jerky is detected by detecting the vibration of the vehicle body, there is a possibility of false detection of a travel jerky occurring even when the vehicle is traveling with the travel pedal being operated by the operator's foot, despite the travel jerky not actually occurring.
In contrast, the present invention determines whether a travel jerky has occurred based on the change in the pressure difference between the target operation pressure and the control operation pressure directly related to the oscillation (vibration) of the travel pedals 54b, 55b, rather than the vibration of the vehicle body. More specifically, the present invention sets a first threshold when the pressure difference is a positive value and a second threshold when the pressure difference is a negative value, and determines whether the number of state transitions between the first travel state where the pressure difference is greater than the first threshold and the second travel state where the pressure difference is smaller than the second threshold has reached a predetermined number of times. Then, when the number of state transitions reaches the predetermined number of times, it is determined that a travel jerky has occurred. Therefore, it is possible to accurately estimate the sway of the travel pedals 54b, 55b, prevent false detection of travel jerky occurrence during the operation of the travel pedals 54b, 55b, and achieve good operability.

(Controller)

FIG. 6 is a functional block diagram showing the processing content of the controller 34.
The controller 34 includes a target operation pressure calculation section 34a, a state determination section 34b, a target pressure correction section 34c, and a solenoid valve control section 34d.
The controller 34 calculates a target operation pressure corresponding to the operation amount based on the operation signals from the operation devices 52, 53 and the travel operation devices 54, 55 in the target operation pressure calculation section 34a.
FIG. 7 is a diagram showing the relationship between the operation signal and the operation amount for calculating the operation amount from the operation signal, and FIG. 8 is a diagram showing the relationship between the operation amount and the target operation pressure for calculating the target operation pressure from the operation amount.
The controller 34 stores the relationship between the operation signal and the operation amount as shown in FIG. 7 for each of the control levers of the operation devices 52, 53 and the control levers and control pedals of the travel operation devices 54, 55. Then, the controller 34, in the target operation pressure calculation section 34a, refers the operation signals of the control levers of the operation devices 52, 53 and the travel operation devices 54, 55 to the relationship between the operation signal and the operation amount shown in FIG. 7 to calculate the corresponding operation amount, and refers the calculated operation amount to FIG. 8 (the relationship between the operation amount and the target operation pressure) to calculate the corresponding target operation pressure.
Next, the controller 34 performs the following processing in the state determination section 34b.

1. The controller 34 obtains the control operation pressure detected by the pressure sensors 35 to 38 and calculates the pressure difference between the calculated target operation pressure and the control operation pressure in the target operation pressure calculation section 34a. Then, the controller 34 determines whether a travel jerky has occurred based on the change in the pressure difference.
2. More specifically, the controller 34 sets a first threshold value "X" when the pressure difference is a positive value and a second threshold value "-X" when the pressure difference is a negative value, and determines whether the number of state transitions between the first travel state where the pressure difference is greater than the first threshold "X" and the second travel state where the pressure difference is smaller than the second threshold "-X" has reached the first predetermined number of times. Then, the controller 34 determines that a travel jerky has occurred when the number of state transitions between the first travel state and the second travel state reaches the first predetermined number of times.
3. In that case, the controller 34 determines whether the number of state transitions has reached the first predetermined number of times within the first predetermined time. Then, the controller 34 determines that a travel jerky has occurred when the number of state transitions reaches the first predetermined number of times within the first predetermined time.
4. The first predetermined number of times is preferably 1 to 3 times.
5. After the controller 34 determines that the number of state transitions has reached the first predetermined number of times and a travel jerky has occurred, it further determines whether the number of state transitions has reached the second predetermined number of times. Then, the controller 34 determines that the travel jerky is continuing when the number of state transitions reaches the second predetermined number of times.
6. In that case, the controller 34 determines whether the number of state transitions has reached the second predetermined number of times within the second predetermined time. Then, the controller 34 determines that the travel jerky is continuing if the number of state transitions reaches the second predetermined number of times within the second predetermined time, and determines that the travel jerky has ended if the number of state transitions does not reach the second predetermined number of times within the second predetermined time.
7. The second predetermined number of times is preferably 1 to 2 times.

Then, when the controller 34 determines that a travel jerky has occurred in the state determination section 34b, it corrects the target operation pressure in the target pressure correction section 34c to limit the rate of change of the target operation pressure. Then, the controller 34 generates a command current corresponding to the corrected target operation pressure in the solenoid valve control section 34d and outputs it to the electromagnetic proportional control valves 20 to 23.
On the other hand, the controller 34 calculates the target operation pressure other than travel using the operation signal and operation amount relationship shown in FIG. 7 and the operation amount and target operation pressure relationship shown in FIG. 8, for the operation signals of the control levers of the operation devices 52, 53, similar to the operation signals of the control levers and control pedals of the travel operation devices 54, 55. Then, the controller 34 directly sends the target operation pressure to the solenoid valve control section 34d, generates a command current corresponding to the target operation pressure, and outputs it to the electromagnetic proportional control valves 24 to 31.

(Control Flow of the Controller)

Next, using FIG. 9, FIG. 10A, FIG. 10B, and FIG. 10C, the part of the processing of the controller 34 related to the operation signals of the control levers and control pedals of the travel operation devices 54, 55 will be explained in detail using a flowchart.
FIG. 9 is a flowchart showing the overall flow of processing of the controller 34. FIG. 10A, FIG. 10B, and FIG. 10C are flowcharts showing the details of the command current generation processing for the electromagnetic proportional control valves 20 to 23 in steps S110, S130, S150, and S170 of the flowchart in FIG. 9.
In FIG. 9, the controller 34 determines whether the left travel lever 54a or travel pedal 54b (left travel lever/pedal) is operated in the forward direction and whether the left forward direction operation signal generated by the signal generation unit 54c has been inputted (step S100), and if the determination is YES, it performs the processing to generate and output the command current for the electromagnetic proportional control valve 20 for the left forward direction (step S110). If the determination in step S100 is NO, the controller 34 determines whether the right travel lever 55a or travel pedal 55b (right travel lever/pedal) is operated in the forward direction and whether the right forward direction operation signal generated by the signal generation unit 55c has been inputted (step S120), and if the determination is YES, it performs the processing to generate and output the command current for the electromagnetic proportional control valve 22 for the right forward direction (step S130).
If the determination in step S120 is NO, the controller 34 determines whether the left travel lever 54a or travel pedal 54b (left travel lever/pedal) is operated in the backward direction and whether the left backward direction operation signal generated by the signal generation unit 54c has been inputted (step S140), and if the determination is YES, it performs the processing to generate and output the command current for the electromagnetic proportional control valve 21 for the left backward direction (step S150). If the determination in step S140 is NO, the controller 34 determines whether the right travel lever 55a or travel pedal 55b (right travel lever/pedal) is operated in the backward direction and whether the right backward direction operation signal generated by the signal generation unit 55c has been inputted (step S160), and if the determination is YES, it performs the processing to generate and output the command current for the electromagnetic proportional control valve 23 for the right backward direction (step S170).
In this way, the controller 34 generates control operation pressure by operating the electromagnetic proportional control valves 20 to 23 for travel through the operation of the travel levers 54a, 55a and travel pedals 54b, 55b.
Furthermore, the controller 34 independently performs travel control for left forward travel operation, right forward travel operation, left backward travel operation, and right backward travel operation.
Next, using the flowcharts shown in FIG. 10A, FIG. 10B, and FIG. 10C, the details of the command current generation processing in steps S110, S130, S150, and S170 of the flowchart in FIG. 9 will be explained.
The processing in steps S110, S130, S150, and S170 is the same except for whether the travel lever/pedal is left or right and whether the operation direction is forward or backward, so it will be explained representatively with the processing of step S110 when the travel lever/pedal is the left travel lever 54a and travel pedal 54b and the operation direction is forward.
In FIG. 10A, the controller 34 first inputs the operation signal of the travel lever 54a or travel pedal 54b (left travel lever/pedal) and calculates the operation amount (step S1). The calculation of this operation amount is performed using the relationship between the operation signal and operation amount shown in FIG. 7, as previously described. Next, the controller 34 inputs the detection signal of the pressure sensor 35 and inputs the control operation pressure generated by the electromagnetic proportional control valve 20 for the left forward direction (step S2).
The controller 34 calculates the target operation pressure corresponding to the operation amount of the travel lever/pedal calculated in step S1 (step S3). The calculation of this target operation pressure is performed using the relationship between the operation amount and target operation pressure shown in FIG. 8, as previously described. Next, the controller 34 calculates the difference (pressure difference) D between the target operation pressure calculated in step S3 and the control operation pressure inputted in step S2 using the following equation (step S4). D = Target Operation Pressure - Control Operation Pressure
Thereafter, the controller 34 determines whether the pressure difference D is greater than the first threshold value "X" (positive value) of the travel operation pressure difference (step S5), and if the determination is YES, it stores the travel state as "state 1" (step S6). "State 1" corresponds to state 1 at time t2 in FIG. 5.
Next, the controller 34 determines whether the pressure difference D is less than the second threshold value "-X" (negative value) of the travel operation pressure difference (step S7), and if the determination is YES, it stores the travel state as "state 2" (step S8). "State 2" corresponds to state 2 at time t1 in FIG. 5. Even if the determination in step S5 is NO, the process proceeds to step S7 to make a similar determination, and if the determination is YES, it proceeds to step S8 and stores the travel state as "state 2" (step S8).
Here, the first threshold value "X" and the second threshold value "-X" of the pressure difference are determined based on the magnitude of the impact of the vibration of the travel pedals 54b, 55b on the vibration of the vehicle body (upper swing body 2) when the travel pedals 54b, 55b are foot-operated for travel. Furthermore, the thresholds "X" and "-X" are determined based on the operation torque of the travel pedals 54b, 55b and the responsiveness of the control operation pressure to the target operation pressure.
When the pilot primary pressure generated by the pilot pump 47 is, for example, 4 MPa, the first threshold value "X" is, for example, 0.1 MPa, and the second threshold value "-X" is, for example, -0.1 MPa.
Also, as will be described in the second embodiment below, by changing the first threshold value "X" and the second threshold value "-X" according to the posture of the front working machine 3 and the travel direction of the vehicle body (forward or backward), it is possible to reduce false detection of travel jerky.
Next, the controller 34 determines whether the previously stored travel state is "state 1" and the currently stored travel state is "state 2" (whether the travel state has switched from state 1 to state 2), or whether the previously stored travel state is "state 2" and the currently stored travel state is "state 1" (whether the travel state has switched from state 2 to state 1) (step S9), and if the determination is YES, it adds 1 to the count value JC of the travel jerky determination (step S10). The initial setting of the count value JC for travel jerky determination is 0.
The YES determination in step S9 corresponds to the case where "state 2" occurs at time t1 and switches to "state 1" at time t2 in FIG. 5, corresponding to one occurrence of the switch between "state 1" (first travel state) and "state 2" (second travel state).
After step S10, proceed to step S11 in FIG. 10B.
If the determination in step S7 is NO, proceed to step S9 to make a similar determination, and if the determination is YES, perform the processing of step S10 and then proceed to step S11 in FIG. 10B.
In step S11 of FIG. 10B, the controller 34 determines whether the previous travel jerky determination is initially set to invalid. If the determination in step S11 is YES, it further determines whether the count value JC of the travel jerky determination is greater than 0 (JC>0) (step S12), and if the determination is YES, it adds 1 to the count value TC of the travel determination time (step S13). The initial setting of the count value TC for travel determination time is 0. Also, if the control cycle of the flowchart is set to 0.01 seconds, "1" of the count value TC for travel determination time corresponds to 0.01 seconds. If the determination in step S12 is NO, proceed to step S18.
The processing when the determination in step S11 is NO will be described later.
After the processing of step S13, the controller 34 determines whether the count value TC of the travel determination time is less than the threshold value Y1 (first predetermined time) of the travel determination time (TC<Y1) (step S14), and if the determination is YES, it further determines whether the count value JC of the travel jerky determination is equal to or greater than the threshold value Z1 (first predetermined number) of the travel jerky determination (JC≧Z1) (step S15).
In this embodiment, the time conversion value of the threshold Y1 (first predetermined time) is, for example, 3 seconds, and if the control cycle of the flowchart is 0.01 seconds, the threshold Y1 is, for example, "300". The threshold Z1 (first predetermined number) is, for example, "1 time".
The threshold Y1 (first predetermined time) for the travel determination time in step S14 and the threshold Z1 (first predetermined number) for the travel jerky determination in step S15 are thresholds for determining whether the frequency of occurrence of the count value JC of the travel jerky determination (i.e., the number of occurrences of the determination YES in step S9 within a predetermined time (in this embodiment, the frequency of state switching between state 1 and state 2)) has reached a number that can be considered as the occurrence of travel jerky. Setting the thresholds Y1 and Z1 as described above, if the determinations in step S14 and step S15 are both YES, the controller 34 determines that a YES determination in step S9 appeared once within 3 seconds (300 control cycles) (in the operating state of Figure 5, a switch from state 2 at time t1 to state 1 at time t2 occurred once) and determines that travel jerky has occurred.
Here, the period at which the travel pedals 54b, 55b vibrate when travel jerky occurs varies depending on the specifications of the hydraulic excavator. The threshold Y1 for the travel determination time in step S14 is set based on the vibration period of the travel pedals 54b, 55b.
Also, the threshold Z1 (first predetermined number) for the travel jerky determination in step S15 is determined based on the frequency at which the state intended by the operator during travel switches between "state 1" and "state 2", rather than during travel vibration. If the number of the threshold Z1 for the travel jerky determination is set smaller, the time until the travel control takes effect when travel jerky starts is shortened, allowing the impact of travel jerky to be quickly resolved. However, this increases the possibility of false detection of travel jerky. If the threshold Z1 for the travel jerky determination is set larger, the possibility of false detection of travel jerky is reduced. However, this increases the time until the travel control takes effect when travel jerky starts, making it more susceptible to the impact of travel jerky. Therefore, the threshold Z1 for the travel jerky determination is determined by balancing the speed of resolving the impact of travel jerky and the prevention of false detection of travel jerky.
In this embodiment, the threshold Z1 (first predetermined number) is set to 1 time, but it may be set to 2 or 3 times to reduce the possibility of false detection. This change in threshold can be made by operating the input section 58a of the monitor 58 shown in Figure 2 to select the desired threshold and transmitting the selected threshold information to the controller 34.
If the threshold Z1 for the travel jerky determination in step S15 is set to "2 times" or more, and the number of occurrences of the determination YES in step S9 in Figure 10B is 1 time, the determination in step S15 becomes NO, and it proceeds to step S18.
Then, if the determination in step S15 is YES, the controller 34 enables the travel jerky determination. Then, the controller 34 resets the count value JC of the travel jerky determination and the count value TC of the travel determination time to 0 (step S16) to determine the continuation of the travel jerky, and proceeds to step S18.
On the other hand, if the determination in step S14 is NO, it is determined that travel jerky did not occur within the threshold Y1 of the travel determination time. Then, the controller 34 resets the count value JC of the travel jerky determination and the count value TC of the travel determination time to 0 (step S17) to continue determining the occurrence of travel jerky, and proceeds to step S18.
In step S18, the controller 34 determines whether the travel jerky determination is valid, and if the determination is YES, applies a first-order low-pass filter to the target operation pressure to correct the target operation pressure (step S19).
Here, the filter time constant τ of the first-order low-pass filter applied to the target operation pressure is determined based on the degree of influence on travel acceleration and deceleration due to the travel lever/pedal vibration of the actual vehicle body (upper swing body 2). Also, as described in the third embodiment mentioned later, the filter time constant τ may be changed based on the magnitude of the pressure difference D between the target operation pressure and the control operation pressure. This allows the effect of the filter to be corrected according to the vibration amplitude of the pedal.
Next, the controller 34 controls the electromagnetic proportional control valves 20 to 23 for travel according to the target operation pressure (step S20).
If the determination in step S18 is NO, it proceeds directly to step S20, and the controller 34 controls the electromagnetic proportional control valves 20 to 23 for travel according to the target operation pressure.
Next, the case where the determination in step S11 is NO will be described.
If the determination in step S11 is NO, it is determined that the travel jerky determination was enabled (travel jerky occurred) in step S16. Then, the controller 34 performs the same processing as steps S13 to S17 to determine the continuation of the subsequent travel jerky.
That is, if the determination in step S11 is NO, the controller 34 adds 1 to the count value TC of the travel determination time (step S21). Then, in step S16 or S17, it is determined whether the count value TC of the travel determination time after resetting the count value TC of the travel determination time to 0 is less than the threshold Y2 (second predetermined time) for the continuation of the travel determination time (TC<Y2) (step S22). If the determination is YES, it is further determined whether the count value JC of the travel jerky determination is equal to or greater than the threshold Z2 (second predetermined number) for the continuation determination of the travel jerky (JC≧Z2) (step S23) .
The threshold Y2 (second predetermined time) for the continuation of the travel determination time takes into account the attenuation of vibration by the filter control in step S19 of Figure 10B. And it is set to "150", equivalent to 1.5 seconds, which is shorter than the threshold Y1 (first predetermined time) for the travel determination time in step S14 of Figure 10B. Also, the threshold Z2 (second predetermined number) for the continuation determination of the travel jerky is set to "1 time", the same as the threshold Z1 (first predetermined number) for the travel jerky determination in step S15 of Figure 10B.
If the determination in step S23 is YES, it is the case where the determination in step S9 was YES. Then, the controller 34 determines that the travel jerky is continuing and resets the count value JC of the travel jerky determination and the count value TC of the travel determination time to 0 (step S24) to continue monitoring the continuation of the travel jerky.
In step S23, if the determination is NO, the determination in step S9 is NO. This is the case where 1 was not added to the count value JC of the travel jerky determination in step S10, and it proceeds to the aforementioned step S18 to perform the processing of steps S18, S19, S20, and step S11.
In step S22, if the determination is NO, it is the case where the travel jerky ended within the threshold Y2 for the continuation of the travel determination time. Then, the controller 34 resets the count value JC of the travel jerky determination and the count value TC of the travel determination time to 0 and invalidates the travel jerky determination (step S25).
If the determination in step S23 is NO, it proceeds to the aforementioned step S18.

(Operation Example)

The flowcharts shown in Figures 10A, 10B, and 10C will be further explained using an operation example. The operation example is for the case where the threshold Z1 for the travel jerky determination is 1 time.

~Operation Example 1~

During normal travel

During normal travel, the pressure difference between the target operation pressure and the control operation pressure does not exceed the first threshold "X" and the second threshold "-X", and the determinations in steps S5, S7, and S9 are NO. Therefore, the travel jerky determination remains invalid as initially set, and in step S20, the electromagnetic proportional control valves 20 to 23 for travel are controlled according to the target operation pressure.
The control flow at this time is as follows.
S1~S4 → S5(NO) → S7(NO) → S9(NO) → S11(YES) → S12(NO) → S18(NO) → S20(No correction of target operation pressure)

~Operation Example 2~

During normal travel, the vehicle body vibrated and state 2 shown in Figure 5 occurred, but the switch from state 2 to state 1 did not occur, and the determination result of travel jerky occurrence was not reached.
In this case, the determination in step S9 is NO, and the count value JC of the travel jerky determination remains at the initial setting of 0. Therefore, the determination in step S12 is also NO, and the travel jerky determination remains invalid, and in step S20, the electromagnetic proportional control valves 20 to 23 for travel are controlled according to the target operation pressure.
The control flow at this time is as follows.
S1 to S4 → S5(NO) → S7(YES) → S8 → S9(NO) → S11(YES) → S12(NO) → S18(NO) → S20(No target operation pressure correction)

~Operation Example 3~

The transition from state 2 to state 1 shown in Figure 5 occurs once, and after it is determined that driving jerky has occurred, if the driving jerky ends within the threshold time Y2 for the continuation of the driving determination time

(3-1) <Operation until the switch from state 2 to state 1 occurs once and it is determined that a travel jerky has occurred>

If it is determined as YES in step S5 or step S7 and NO in step S9, and then determined as YES in step S7 or step S5 and YES in step S9 (when the switch between state 1 and state 2 occurs), the count value JC of the travel jerky determination becomes 1 in step S10 (it is determined that a travel jerky has occurred). Therefore, the determination in step S12 becomes YES, and in step S13, 1 is added to the count value TC of the travel determination time. At this time, the count value TC of the travel determination time is within the threshold Y1 of the travel determination time, and it is determined as YES in step S14. Also, as mentioned above, in this operation example, the threshold Z1 for travel jerky determination is 1 (once), and the determination in step S15 becomes YES, and in step S16, the travel jerky determination becomes effective. As a result, the determination in step S18 becomes YES, and in step S19, a correction is made by applying a first-order low-pass filter to the target operation pressure. Then, in step S20, according to the corrected target operation pressure, the travel electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.
The control flow at this time is as follows.

(1) If the previously stored travel state was "state 1"
S1 to S4 → S5 (NO) → S7 (YES) → S8 → S9 (YES) → S10 → S11(YES) → S12(YES) → S13 → S14 (YES) → S15(YES) → S16 → S18 (YES) → S19 → S20 (Target operation pressure correction present)
(2) If the previously stored travel state was "state 2"
S1 to S4 → S5 (YES) → S6 → S7 (NO) → S9 (YES) → S10 → S11(YES) → S12(YES) → S13 → S14 (YES) → S15(YES) → S16 → S18 (YES) → S19 → S20 (Target operation pressure correction present)

(3-2) <Operation after it is determined that a travel jerky has occurred>

After that, if the switch between state 1 and state 2 does not occur, step S9 is NO. And, since the travel jerky determination is effective due to the processing in step S16, the determination in step S11 is also NO. Also, within the threshold Y2 time of the travel determination time continuation in step S22, the determination in step S22 is YES, and the determination in step S23 is NO. Therefore, the process proceeds to steps S18, S19, S20, where the target operation pressure is corrected, and based on the corrected target operation pressure, the electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.
The control flow at this time is as follows.
S1 to S4 → S5 (YES) → S6 → S7(NO) → S9(NO) → S11 (NO) → S21 → S22 (YES) → S23(NO) → S18(YES) → S19 → S20 (Target operation pressure correction present)
In this way, after it is determined that a travel jerky has occurred, the target operation pressure is corrected, and based on the corrected target operation pressure, the electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.

(3-3) <Operation at the end of travel jerky>

After that, the travel jerky ends within the threshold Y2 time of the travel determination time continuation in step S22. Then, the determination in step S22 becomes NO, and in step S25, the count value JC of the travel jerky determination and the count value TC of the travel determination time are reset to 0, and the travel jerky determination becomes invalid. As a result, the determination in step S18 becomes NO, and the correction process of the target operation pressure in step S19 ends. Then, in step S20, according to the target operation pressure, the travel electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.
The control flow at this time is as follows.
S1 to S4 → S5 (YES) → S6 → S7(NO) → S9(NO) → S11 (NO) → S21 → S22(NO) → S25 → S18(NO) → S20(No target operation pressure correction)

~Operation Example 4~

After the operation of (3-2) in Operation Example 3, if the switch between state 1 and state 2 occurs again within the threshold Y2 time of the travel determination time continuation, it is determined as YES in step S5 or step S7 after the operation of (3-2) in Operation Example 3. Then, when the determination in step S9 becomes YES, the count value JC of the travel jerky determination becomes 1 in step S10. Also, due to the processing in step S16, the travel jerky determination is effective, so the determination in step S11 is NO, and the process proceeds to steps S21, S22, S23. Then, the determination in step S23 becomes YES (it is determined that the travel jerky is continuing), and in step S24, the count value JC of the travel jerky determination and the count value TC of the travel determination time are reset to 0. After this, the process proceeds to steps S18, S19, S20, where the target operation pressure is corrected, and based on the corrected target operation pressure, the electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.
The control flow at this time is as follows.

(1) If the previously stored travel state was "state 1"
S1 to S4 → S5(NO) → S7(YES) → S8 → S9(YES) → S11(NO) - S21 → S22 (YES) → S23(YES) → S24 → S18(YES) → S19 → S20(Target operation pressure correction present)
(2) If the previously stored travel state was "state 2"
S1 to S4 → S5(YES) → S6 → S7(NO) → S9(YES) → S11(NO) → S21 → S22 (YES) → S23(YES) → S24 → S18(YES) → S19 → S20(Target operation pressure correction present)

After that, when the travel jerky ends within the threshold Y2 time of the travel determination time continuation in step S22, the correction process of the target operation pressure in step S19 ends as in (3-3) of Operation Example 3, and in step S20, according to the target operation pressure, the travel electromagnetic proportional control valves 20 to 23 are controlled, thereby controlling the travel motors 1a, 1b.

(Effect)

According to this embodiment configured as described above, the following effects can be obtained.

1. Figure 11 is a diagram showing the basic effects obtained by the travel control of this embodiment. The left side of the figure shows the changes in target operation pressure and control operation pressure before the application of control in this embodiment, and the right side of the figure shows the changes in target operation pressure and control operation pressure after the application of control in this embodiment.
By performing the travel control of this embodiment, the target operation pressure is corrected as shown by the dotted line on the right side of Figure 11, and the travel electromagnetic proportional control valves 20 to 23 are controlled by the command current generated based on the corrected target operation pressure. As a result, the control operation pressure output from the electromagnetic proportional control valves 20 to 23 is corrected as shown by the solid line on the right side of Figure 11, allowing the influence of the travel jerky to be terminated early.
2. In this embodiment, instead of the vibration of the vehicle body, the occurrence of driving jerky is determined based on the number of state switching when the change in the pressure difference between the target operation pressure and the control operation pressure, which directly relates to the vibration (oscillation) of the driving control pedals 54b, 55b, exceeds the threshold "X" or "-X" (when the number of state switches between the first travel state with a pressure difference greater than the first threshold "X" and the second travel state with a pressure difference less than the second threshold "-X" reaches the first predetermined number, it is determined that a travel jerky has occurred). Therefore, the sway of the travel pedals 54b, 55b can be accurately estimated, preventing false detection of travel jerky occurrence during the operation of the travel control pedals 54b, 55b. As a result, the decrease in responsiveness of travel operation due to the first-order low-pass filter (signal smoothing means) that occurs when a travel jerky occurrence is falsely detected can be prevented, achieving good operability.
3. Additionally, the controller 34 determines whether the number of state switches has reached the first predetermined number Z1 within the first predetermined time Y1. Then, when the number of state switches reaches the first predetermined number Z1 within the first predetermined time Y1, it is determined that a travel jerky has occurred, allowing the occurrence of a travel jerky to be determined based on the frequency of state switches. As a result, the sway of the travel pedals 54b, 55b can be estimated more accurately, further reducing false detection of travel jerky occurrence.
4. Furthermore, the controller 34 determines whether the number of state transitions has reached a first predetermined number 21, and after determining that travel jerky has occurred, it further determines whether the number of state transitions has reached a second predetermined number Z2. Then, if the number of state transitions reaches the second predetermined number Z2, it is determined that the travel jerky is continuing. This allows for accurate estimation of the continuation of travel jerky after its occurrence.
5. Additionally, the controller 34 determines whether the number of state transitions has reached the second predetermined number Z2 within a second predetermined time Y2. Then, if the number of state transitions reaches the second predetermined number Z2 within the second predetermined time Y2, it is determined that the travel jerky is continuing, and if it does not reach the second predetermined number Z2 within the second predetermined time Y2, it is determined that the travel jerky has ended. This allows for the determination of the continuation of travel jerky based on the frequency of state transitions, enabling more accurate estimation of travel jerky continuation.

The second embodiment of the present invention will be described with reference to FIGS. 1, 2, 12, and 14 to 17.
In FIG. 1, the hydraulic control system of this embodiment includes an angle sensor 60 that detects the posture of the front working machine 3 of the hydraulic excavator. The angle sensor 60 is provided on the boom 3a and is an angle sensor such as an inertial sensor that detects the angle (boom angle) of the boom 3a relative to the horizontal direction.
FIG. 12 is a functional block diagram showing the processing content of the controller in the second embodiment of the present invention, and FIG. 13 is a functional block diagram showing the details of the state determination section 34b of the controller 34.
In FIG. 12, the controller 34 of this embodiment inputs the operation signals from the operation devices 52, 53 and travel operation devices 54, 55, as well as the detection signals from pressure sensors 35 to 38, in addition to the detection signal from the angle sensor 60.
In FIG. 13, the state determination section 34b of the controller includes a state determination processing section 34bA and a pressure difference threshold determination section 34bB. Then, the state determination processing section 34bA inputs the operation signals from the operation devices 52, 53 and travel operation devices 54, 55, as well as the detection signals from pressure sensors 35 to 38, and performs the aforementioned processing described using the flowcharts shown in FIGS. 9 and 10A to 10C.
The pressure difference threshold determination section 34bB inputs the posture information (boom angle) of the front working machine 3 based on the detection signal from the angle sensor 60. Then, the pressure difference threshold determination section 34bB determines the first threshold "X" and the second threshold "-X" for the pressure difference such that the absolute value increases as the front working machine 3 rotates downward and its posture approaches horizontal.
The pressure difference threshold determination section 34bB determines whether the travel direction indicated by the operation signal from the travel operation devices 54, 55 is forward or reverse. Then, the pressure difference threshold determination section 34bB determines the first threshold "X" and the second threshold "-X" for the pressure difference such that the absolute value is larger when the travel direction is forward than when it is reverse.
FIG. 14 is a flowchart showing an example of the processing by the pressure difference threshold determination section 34bB. FIG. 15 is a diagram showing the relationship between the boom angle and the first threshold coefficient K1 used in the processing by the pressure difference threshold determination section 34bB. FIG. 16 is a diagram showing in tabular form the relationship between the second threshold coefficient when the travel direction is forward and when it is reverse.
In FIG. 15, the pressure difference threshold determination section 34bB inputs the boom angle as posture information of the boom 3a from the detection signal of the angle sensor 60. Then, the pressure difference threshold determination section 34bB refers to the relationship between the boom angle and the first threshold coefficient K1 shown in FIG. 15 to calculate the corresponding first threshold coefficient K1 (step S210). The relationship between the boom angle and the first threshold coefficient K1 in FIG. 15 is set such that the first threshold coefficient K1 increases as the boom angle decreases (as the front working machine 3 approaches a horizontal posture), and is stored in the controller 34.
Next, the pressure difference threshold determination section 34bB determines whether the travel direction indicated by the operation signal from the travel operation devices 54, 55 is forward or reverse. Then, the pressure difference threshold determination section 34bB refers to the relationship between the determined travel direction and the second threshold coefficient K2 shown in FIG. 16, and determines the second threshold coefficient K2 corresponding to the travel direction (step S220). The table in Figure 16 states that when the travel direction is forward, the second threshold coefficient K2 is less than 1, for example, 0.8, and when the travel direction is reverse, the second threshold coefficient K2 is greater than 1, for example, 1.2. Then, the relationship between these travel directions and the second threshold coefficient K2 is set and stored in the controller 34.
Next, the pressure difference threshold determination section 34bB calculates the first threshold "X" and the second threshold "-X" for the pressure difference from the following formula (step S230).
First threshold "X" = Basic threshold "X0" × K1 × K2 Second threshold "-X" = Basic threshold "-X0" × K1 × K2
The basic threshold "X0" is a predetermined value based on the operation torque of the travel pedals 54b, 55b, and is stored in the controller 34.
FIG. 17 is a diagram showing the relationship between the operation torque of the travel pedals 54b, 55b and the basic threshold "X0" when determining the basic threshold "X0" based on the operation torque of the travel pedals. As shown in this figure, the basic threshold "X0" is set at the time of machine shipment to increase as the operation torque of the travel pedals 54b, 55b decreases.
The operation torque of the travel pedals 54b, 55b affects the ease of stepping (stepping force) when the operator steps with their foot. Then, when the operation torque of the travel pedals 54b, 55b is small, the vibration (sway) of the travel pedals 54b, 55b due to foot operation becomes large in response to vehicle body vibration, so it is necessary to increase the absolute values of the first threshold "X" and the second threshold "-X" accordingly. On the other hand, there is some variation in the operation torque of the travel pedals 54b, 55b at the time of machine shipment, and the first threshold "X" and the second threshold "-X" need to be set considering this variation.
As shown in FIG. 17, the basic threshold "X0" is set to increase as the operation torque of the travel pedals 54b, 55b decreases. This absorbs the variation in the operation torque of the travel pedals 54b, 55b at the time of machine shipment, resulting in appropriate values for the first threshold "X" and the second threshold "-X".
In this embodiment, by determining the first threshold "X" and the second threshold "-X" for the pressure difference as described above, the first threshold "X" and the second threshold "-X" for the pressure difference are determined to increase in absolute value as the front working machine 3 rotates downward and its posture approaches horizontal. Additionally, the first threshold "X" and the second threshold "-X" for the pressure difference are determined to have larger absolute values when the travel direction indicated by the operation signal from the travel operation devices 54, 55 is forward rather than reverse.
According to this embodiment, the following effects are obtained.
The magnitude (amplitude) of vehicle body vibration when a hydraulic excavator travels on uneven ground varies depending on the posture of the front working machine 3 and the travel direction, and the ease of occurrence of travel jerky also varies.
That is, when the boom angle is small and the posture of the front working machine 3 is close to horizontal, the vehicle body is prone to sway, resulting in large vehicle body vibration and easy occurrence of travel jerky. On the other hand, when the boom angle is large and the posture of the front working machine 3 is close to vertical, the vehicle body is less prone to sway, resulting in small vehicle body vibration and less likelihood of travel jerky occurrence.
Additionally, when the vehicle body is driven in the forward direction, the operator pushes the control pedal forward F (see FIG. 2), causing the operator's upper body to move away from the seat backrest, making the operator's upper body prone to sway and travel jerky likely to occur. On the other hand, when the vehicle body is driven in the reverse direction, the operator pushes the control pedal backward R (see FIG. 2), causing the operator's upper body to be held against the seat backrest, making the operator's upper body less prone to sway and travel jerky less likely to occur.
Therefore, regardless of the posture of the front working machine 3 or the travel direction, using the same values for the first threshold "X" and the second threshold "-X" may result in false detection of travel jerky occurrence.
In this embodiment, as described above, the first threshold "X" and the second threshold "-X" are corrected according to the posture of the front working machine 3 and the travel direction, reducing false detection of travel jerky occurrence.
In this embodiment, an angle sensor 60 is used to detect the posture of the front working machine 3 by detecting the angle (boom angle) of the boom 3a, but in addition to the boom angle, an angle sensor for detecting the angle (arm angle) of the arm 3b may be further provided, and the posture of the front working machine 3 may be detected by the combination of the boom angle and the arm angle. This allows for more accurate detection of the posture of the front working machine 3, further reducing false detection of travel jerky occurrence.

The third embodiment of the present invention will be described with reference to FIGS. 18 to 20.
FIG. 18 is a functional block diagram showing details of the state determination section 34b of the controller 34 in the third embodiment of the present invention.
In FIG. 18, the state determination section 34b of the controller includes a state determination processing section 34bA and a filter time constant calculation section 34bC. The state determination processing section 34bA inputs operation signals from the operation devices 52, 53 and the travel operation devices 54, 55, as well as detection signals from the pressure sensors 35 to 38, and performs the aforementioned processing described using the flowcharts shown in FIGS. 9 and 10A to 10C.
The filter time constant calculation section 34bC estimates the magnitude (amplitude) of the vibration of the travel pedals 54b, 55b based on the pressure difference D calculated in step S4 of FIG. 10A, and determines the degree of limitation of the rate of change of the target operation pressure according to the magnitude (amplitude) of the vibration of the travel pedals 54b, 55b.
FIG. 19 is a diagram showing the relationship between the pressure difference D of the target operation pressure and the control operation pressure used for estimating the magnitude of the vibration of the travel pedals 54b, 55b and the magnitude of the vibration of the travel pedals 54b, 55b. FIG. 20 is a diagram showing the relationship between the magnitude of the vibration of the travel pedals 54b, 55b and the filter time constant τ.
The filter time constant calculation section 34bC refers to the relationship between the pressure difference D of the target operation pressure and the control operation pressure calculated in step S4 of FIG. 10A, as shown in FIG. 19, and the magnitude of the vibration of the travel pedals 54b, 55b, and calculates the corresponding magnitude of the vibration of the travel pedals 54b, 55b. The relationship between the pressure difference D and the magnitude of the vibration of the travel pedals 54b, 55b shown in FIG. 20 is set such that the magnitude of the vibration of the travel pedals 54b, 55b increases as the pressure difference D increases, and is stored in the controller 34.
The filter time constant calculation section 34bC also refers to the relationship between the magnitude of the vibration of the travel pedals 54b, 55b shown in FIG. 20 and the filter time constant τ, and calculates the corresponding filter time constant τ. The relationship between the magnitude of the vibration of the travel pedals 54b, 55b and the filter time constant τ shown in FIG. 21 is set such that the filter time constant τ increases as the magnitude of the vibration of the travel pedals 54b, 55b increases, and is stored in the controller 34.
The filter time constant τ calculated using FIG. 20 is used in the filter processing of step S19 of FIG. 10B, and the degree of limitation of the rate of change of the target operation pressure is determined according to the magnitude of the vibration of the travel pedals 54b, 55b.
By determining the filter time constant τ based on the magnitude of the pressure difference D between the target operation pressure and the control operation pressure, the action of the low-pass filter can be corrected according to the magnitude (amplitude) of the vibration of the travel pedals 54b, 55b, thereby improving the attenuation performance of the low-pass filter. As a result, the limiting action on the rate of change of the target operation pressure is improved, and the travel jerky can be quickly suppressed.
In the second embodiment, the state determination section 34b of the controller 34 is configured to include a pressure difference threshold determination section 34bB, and in the third embodiment, the state determination section 34b of the controller 34 is configured to include a filter time constant calculation section 34bC. However, by combining the second and third embodiments, the state determination section 34b may be configured to include both the pressure difference threshold determination section 34bB and the filter time constant calculation section 34bC.

(Others)

In the above embodiments, the travel operation devices 54, 55 are electric types that generate electric signals as operation signals, but they may also be hydraulic pilot types that generate operation pilot pressure as operation signals. In that case, the operation amount of the control lever is detected by the IMU sensor, and the target operation pressure is calculated within the controller 34, while similarly to the above-described embodiments, the control operation pressure guided to the travel switching control valves 13, 14 is detected by the pressure sensors 35 to 38, and the control operation pressure is calculated within the controller 34, and similar processing to the operation signals of the electric travel operation devices 54, 55 is performed based on the target operation pressure and the control operation pressure. Additionally, travel electromagnetic proportional control valves 20 to 23 are arranged in the oil passage leading the operation pilot pressure to the travel switching control valves 13, 14, and when the occurrence of travel jerky is not detected, the travel electromagnetic proportional control valves 20 to 23 are fully opened, and when the occurrence of travel jerky is detected, the electromagnetic proportional control valves 20 to 23 are controlled as in the above-described embodiments.

Description of Reference Characters

1: lower travel body
2: upper swing body
3: front working machine
1a,1b: travel motor
1a,1b,2a,3d,3e,3f: multiple actuators
3a: boom
3b: arm
3c: bucket
4: cabin
6: hydraulic pump
13-18: switching control valve
13,14: travel switching control valve
20-31: electromagnetic proportional control valve
20-23: travel electromagnetic proportional control valve
34: controller
35,36,37,38: pressure sensor
52,53: operation device
52a,53a: control lever
54,55: operation device (travel operation device)
54a,55a: control lever (travel control lever, travel lever)
54b,55b: control pedal (travel control pedal, travel pedal)
52c,53c,54c,55c: signal generation unit
X: first threshold
-X: second threshold
Y1: travel determination time threshold (first predetermined time)
Y2: travel determination time continuation threshold (second predetermined time)
Z1: travel jerky determination threshold (first predetermined number of times)
Z2: travel jerky continuation determination threshold (second predetermined number of times)

Claims

A hydraulic control system for construction machine comprising:
multiple actuators driven by pressure oil discharged from a hydraulic pump, including a travel motor;

multiple switching control valves including a travel switching control valve that controls the flow of pressure oil discharged from the hydraulic pump and supplied to the travel motor;

multiple operation devices including a travel control lever and a travel control pedal positioned adjacent to the base end of the travel control lever, which generate operation signals according to the operation amount of the travel control lever and travel control pedal;

a controller that calculates a target operation pressure based on the operation signal of the travel operation device according to the operation amount, and generates a command current according to the target operation pressure, and limits the rate of change of the target operation pressure by correcting the target operation pressure when it is determined that travel jerky has occurred; and

a travel electromagnetic proportional control valve that generates a control operation pressure according to the command current and operates the travel switching control valve;

wherein the hydraulic control system further comprises a pressure sensor that detects the control operation pressure generated by the travel electromagnetic proportional control valve; and

wherein the controller calculates the target operation pressure based on the operation signal of the travel operation device according to the operation amount of the travel control lever and travel control pedal; and

inputs the control operation pressure detected by the pressure sensor, calculates the pressure difference between the target operation pressure and the control operation pressure, and determines whether travel jerky has occurred based on the change in the pressure difference.
The hydraulic control system for construction machine according to claim 1;
wherein the controller sets a first threshold when the pressure difference is a positive value and a second threshold when the pressure difference is a negative value; and

determines whether the number of state switching between a first driving state, where the pressure difference is greater than the first threshold, and a second driving state, where the pressure difference is less than the second threshold, has reached a first predetermined number, then if the number of state switching has reached the first predetermined number, the controller determines that driving jerky has occurred.
The hydraulic control system for construction machine according to claim 2;
wherein the controller determines whether the number of state switching has reached the first predetermined number of times within the first predetermined time, and determines that travel jerky has occurred when the number of state switching reaches the first predetermined number of times within the first predetermined time.
The hydraulic control system for construction machine according to claim 2;
wherein the first predetermined number of times is 1 to 3 times.
The hydraulic control system for construction machine according to claim 2;
wherein the controller, after determining that the number of state switching has reached the first predetermined number of times and that travel jerky has occurred, further determines whether the number of state switching has reached the second predetermined number of times, and determines that travel jerky is continuing when the number of state switching reaches the second predetermined number of times.
The hydraulic control system for construction machine according to claim 5;
wherein the controller determines whether the number of state switching has reached the second predetermined number of times within the second predetermined time, and determines that travel jerky is continuing when the number of state switching reaches the second predetermined number of times within the second predetermined time, and determines that travel jerky has ended when the number of state switching does not reach the second predetermined number of times within the second predetermined time.
The hydraulic control system for construction machine according to claim 5;
wherein the second predetermined number of times is 1 to 2 times.
The hydraulic control system for construction machine according to claim 2;
wherein the construction machine includes an upper swing body and a front working machine mounted on the front of the upper swing body to be rotatable in the vertical direction for performing work;

wherein the hydraulic control system further comprises an angle sensor that detects the posture of the front working machine; and

wherein the controller inputs posture information of the front working machine based on the detection signal of the angle sensor and determines the first threshold and the second threshold of the pressure difference such that the absolute value increases as the front working machine rotates downward and its posture approaches horizontal.
The hydraulic control system for construction machine according to claim 2;
wherein the controller determines whether the travel direction indicated by the operation signal of the travel operation device is the forward direction or the reverse direction, and determines the first threshold and the second threshold of the pressure difference such that the absolute value is greater when the travel direction is the forward direction than when it is the reverse direction.
The hydraulic control system for construction machine according to claim 1;
wherein the controller estimates the magnitude of vibration of the travel control pedal based on the pressure difference and determines the degree of limitation of the rate of change of the target operation pressure according to the magnitude of vibration of the travel operating pedal.