CN111148906A - Hydraulic shovel drive system - Google Patents
Hydraulic shovel drive system Download PDFInfo
- Publication number
- CN111148906A CN111148906A CN201880064787.4A CN201880064787A CN111148906A CN 111148906 A CN111148906 A CN 111148906A CN 201880064787 A CN201880064787 A CN 201880064787A CN 111148906 A CN111148906 A CN 111148906A
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- Prior art keywords
- arm
- electromagnetic proportional
- proportional valve
- pressure
- bucket
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
- F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
Abstract
The hydraulic shovel drive system is provided with: a control valve for a cylinder for swinging the swing portion; an operation device that outputs an operation signal corresponding to a tilt angle of the operation lever when receiving a first operation; a solenoid proportional valve connected to a first pilot port for a first operation of the control valve; and a control device for controlling the electromagnetic proportional valve; the control device controls the solenoid valve in the following manner: when the operation device receives the first operation, the secondary pressure output from the electromagnetic proportional valve changes from zero to a maximum value in accordance with the operation signal when the pressure of the hydraulic oil supplied from the pump to the cylinder is greater than a threshold value, and the secondary pressure output from the electromagnetic proportional valve is limited to a set value that is less than the maximum value when the pressure of the hydraulic oil supplied from the pump to the cylinder is less than the threshold value.
Description
Technical Field
The present invention relates to a hydraulic shovel drive system.
Background
In general, in a hydraulic excavator, an arm that tilts with respect to a revolving structure is swingably connected to a distal end of the arm, and a bucket is swingably connected to a distal end of the arm. The drive system mounted on this hydraulic excavator includes a boom cylinder for tilting a boom, an arm cylinder for swinging an arm, a bucket cylinder for swinging a bucket, and the like, and these hydraulic actuators are supplied with hydraulic oil from a pump via a control valve.
For example, patent document 1 discloses a hydraulic shovel drive system 100 as shown in fig. 10. In the drive system 100, the supply and discharge of the hydraulic oil to and from the arm cylinder 110 are controlled by the control valve 150. The control valve 150 has a pair of pilot ports connected to the pilot operation valve 140, and the opening area on the inlet throttle side and the opening area on the outlet throttle side of the control valve 150 increase as the pilot pressure introduced into the control valve 150 increases.
In the drive system 100, a pilot on-off valve 120 is provided in a supply/discharge line connecting the rod side oil chamber 112 of the arm cylinder 110 and the control valve 150. The pilot on-off valve 120 operates when the pressure in the bottom side oil chamber 111 of the arm cylinder 110 is reduced to a predetermined pressure or less, and reduces the opening degree of a passage for the hydraulic oil discharged from the rod side oil chamber 112 of the arm cylinder 110. This prevents the arm cylinder 110 from extending due to the weight of the entire arm and bucket during the arm pulling operation, and prevents cavitation from occurring in the arm cylinder 110.
Prior art documents:
patent documents:
patent document 1: japanese patent laid-open No. 5-187409.
Disclosure of Invention
The problems to be solved by the invention are as follows:
however, in the drive system 100 shown in fig. 10, in addition to the pilot on-off valve 120, a pressure reducing valve 130 is required as a valve for operating the pilot on-off valve 120, and the pressure reducing valve 130 reduces the pilot pressure introduced from the pilot operation valve 140 to the pilot on-off valve 120 in accordance with the pressure in the bottom side oil chamber 111 of the arm cylinder 110. Therefore, the structure of the drive system 100 is complicated and the cost is high.
Accordingly, an object of the present invention is to provide a hydraulic shovel drive system that can prevent cavitation from occurring due to the influence of gravity in a cylinder that swings an arm or a bucket with a simple structure.
Means for solving the problems:
in order to solve the above problem, a hydraulic shovel drive system according to the present invention includes: a cylinder configured to swing a swing portion that is a boom or a bucket; a control valve that controls supply and discharge of hydraulic oil to and from the cylinder, and that has a first pilot port for a first operation of swinging the swing portion in one direction and a second pilot port for a second operation of swinging the swing portion in a direction opposite to the one direction; an operation device including an operation lever that outputs an operation signal corresponding to a tilt angle of the operation lever when receiving the first operation; an electromagnetic proportional valve connected to the first pilot port; a pressure sensor that detects at least a pressure of the working oil supplied from the pump to the cylinder at the first operation; and a control device for controlling the electromagnetic proportional valve; when the operation device receives the first operation, the control device controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve changes from zero to a maximum value in accordance with the operation signal when the pressure detected by the pressure sensor is greater than a threshold value, and controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve is limited to a set value smaller than the maximum value or less when the pressure detected by the pressure sensor is smaller than the threshold value.
According to the above configuration, in the first operation, when the pressure of the hydraulic oil supplied from the pump to the cylinder is lowered by the gravity acting on the swing portion so as to accelerate the swing of the swing portion, the secondary pressure output from the electromagnetic proportional valve is limited to the set value or less. That is, at this time, the opening area of the control valve on the outlet throttle side is limited to a predetermined value or less. Therefore, cavitation in the cylinder due to the influence of gravity can be prevented. Further, compared to the conventional drive system 100 shown in fig. 10, the above-described effects can be obtained by controlling the electromagnetic proportional valve without the pilot on-off valve 120 and the pressure reducing valve 130, and therefore, the drive system can be made to have a simple configuration. In particular, in the case where the operating device is an electric joystick, no additional equipment is required, and the hydraulic excavator drive system of the present invention can be realized at low cost.
The threshold may be a first threshold; the control device measures a time from a time when the pressure detected by the pressure sensor is lower than a second threshold value that is larger than the first threshold value to a time when the pressure becomes a third threshold value between the first threshold value and the second threshold value, controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve changes from zero to a maximum value in accordance with the operation signal if the measured time is larger than a reference time, and controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve is limited to the set value or less if the measured time is smaller than the reference time; the control device compares the first threshold value with the pressure detected by the pressure sensor when the measured time is greater than the reference time. According to this configuration, the first threshold value can be set low, and a large opening area on the outlet throttle side can be ensured for a long time when the time from when the pressure detected by the pressure sensor falls below the second threshold value to when the pressure reaches the third threshold value is long, in other words, when the influence of gravity on the swing portion is small. Thus, for example, when the swing portion is an arm and the first operation is an arm pulling operation, a range (a pressure range of the pump) in which the pressure on the outlet throttle side during excavation can be reduced can be widened. Therefore, the fuel consumption rate during excavation can be reduced.
The invention has the following effects:
according to the present invention, cavitation caused by the influence of gravity in a cylinder for swinging an arm or a bucket can be prevented with a simple configuration.
Drawings
Fig. 1 is a schematic configuration diagram of a hydraulic shovel drive system according to a first embodiment of the present invention;
fig. 2 is a side view of the hydraulic excavator;
FIG. 3 is a graph showing the relationship of an operating signal to the secondary pressure of the solenoid proportional valve;
FIG. 4 is a graph showing the relationship of pilot pressure acting on the control valve and the opening area on the outlet throttle side of the control valve;
fig. 5 is a flowchart of control by the control device;
FIG. 6 is a flowchart of a modification of the first embodiment;
fig. 7 is a graph showing a temporal change in discharge pressure of the main pump when the arm pulling operation is performed from a state in which the arm is horizontal;
fig. 8 is a graph showing a temporal change in discharge pressure of the main pump when the arm pulling operation is performed from a state in which the arm is inclined downward;
fig. 9 is a schematic configuration diagram of a hydraulic shovel drive system according to a second embodiment of the present invention;
fig. 10 is a schematic configuration diagram of a conventional hydraulic shovel drive system.
Detailed Description
(first embodiment)
Fig. 1 shows a hydraulic shovel drive system 1A according to a first embodiment of the present invention, and fig. 2 shows a hydraulic shovel 10 equipped with the drive system 1A.
The hydraulic excavator 10 shown in fig. 2 is self-propelled and includes a traveling body 11. The hydraulic excavator 10 includes a revolving structure 12 supported rotatably by the traveling structure 11, and a boom 13 that is tilted with respect to the revolving structure 12. A tip end of the boom 13 is swingably connected to an arm 14, and a tip end of the arm 14 is swingably connected to a bucket 15. The revolving structure 12 is provided with an operator's cab 16 in which an operator's seat is provided.
As shown in fig. 1, the drive system 1A includes, as hydraulic actuators, a pair of left and right travel motors and a turning motor (not shown), and includes an arm cylinder 21 (see fig. 2), an arm cylinder 22, and a bucket cylinder 23. The arm cylinder 21 tilts the arm 13, the arm cylinder 22 swings the arm 14, and the bucket cylinder 23 swings the bucket 15.
The hydraulic actuator is supplied with hydraulic oil from the main pump 31 via a control valve. The main pump 31 is driven by the engine 30. For example, hydraulic oil is supplied to arm cylinder 22 via arm control valve 41, and hydraulic oil is supplied to bucket cylinder 23 via bucket control valve 44. The other control valves for the hydraulic actuator are not shown. The main pump 31 may be a single-stage pump or a double-stage pump. In fig. 1, an unloading valve, a relief valve, and the like for allowing the hydraulic oil discharged from the main pump 31 to escape to the accumulator are also omitted.
Specifically, the arm control valve 41 and the bucket control valve 44 are connected to the main pump 31 through the supply line 32. The arm control valve 41 and the bucket control valve 44 are connected to the tank through the tank line 35.
The bucket control valve 44 is connected to the bucket cylinder 23 through a bucket excavation supply line 23a and a bucket dumping supply line 23 b. The bucket control valve 44 controls supply and discharge of the hydraulic oil to and from the bucket cylinder 23. The bucket control valve 44 has a pilot port 45 for a bucket excavation operation for swinging the bucket 15 in a direction approaching the cab 16, and a pilot port 46 for a bucket dumping operation for swinging the bucket 15 in a direction away from the cab 16.
The arm electromagnetic proportional valves 61 and 62 and the bucket electromagnetic proportional valves 63 and 64 are connected to the sub pump 33 through the primary pressure line 34. The sub-pump 33 is driven by the engine 30, similarly to the main pump 31.
In the present embodiment, each of the solenoid proportional valves 61 to 64 is a proportional type in which the output secondary voltage and the command current are positively correlated. However, the electromagnetic proportional valves 61 to 64 may be of an inverse proportional type in which the output secondary voltage and the command current are inversely related to each other.
The drive system 1A includes an arm operation device 71 for operating the arm control valve 41 and a bucket operation device 72 for operating the bucket control valve 44. The arm operation device 71 includes an operation lever, and outputs an arm operation signal Sa (an arm pulling operation signal or an arm pushing operation signal) corresponding to a tilting angle of the operation lever when receiving either of the arm pulling operation and the arm pushing operation. The bucket operating device 72 includes an operating lever, and outputs a bucket operation signal Sb (bucket excavation operation signal or bucket dumping operation signal) corresponding to the dump angle of the operating lever when receiving either of the bucket excavation operation and the bucket dumping operation.
In the present embodiment, each of the arm operation device 71 and the bucket operation device 72 is an electric joystick that outputs an electric signal as an operation signal (Sa or Sb). The arm operation signal Sa output from the arm operation device 71 and the bucket operation signal Sb output from the bucket operation device 72 are input to the control device 8.
The arm operation signal Sa output from the arm operation device 71 may be larger as the dump angle of the operation lever is larger in each of the arm pulling operation and the arm pushing operation. Alternatively, when the arm operation device 71 outputs a constant current or voltage even when the operation lever is in the neutral state, the arm operation signal Sa may be larger when the tilt angle of the operation lever is larger in one of the arm pulling operation and the arm pushing operation, and may be smaller when the tilt angle of the operation lever is larger in the other of the arm pulling operation and the arm pushing operation. Similarly, the bucket operation signal Sb output from the bucket operating device 72 may be set to be larger as the dump angle of the operating lever is larger in each of the bucket excavating operation and the bucket dumping operation. Alternatively, when the bucket operating device 72 outputs a constant current or voltage even when the operating lever is in the neutral state, the bucket operation signal Sb may be set to be larger when the tip angle of the operating lever is larger in one of the bucket excavation operation and the bucket dumping operation, and may be set to be smaller when the tip angle of the operating lever is larger in the other of the bucket excavation operation and the bucket dumping operation.
The controller 8 is a computer having a Memory such as a ROM (Read-Only Memory) or a RAM (Random access Memory) and a CPU (Central Processing Unit), and a program stored in the ROM is executed by the CPU. The controller 8 controls the arm electromagnetic proportional valves 61 and 62 based on the arm operation signal Sa, and controls the bucket electromagnetic proportional valves 63 and 64 based on the bucket operation signal Sb. In addition, only a part of the signal lines are illustrated in fig. 1 for simplicity.
Specifically, the controller 8 supplies a command current to the arm electromagnetic proportional valve 61 during the arm pulling operation, and supplies a command current to the arm electromagnetic proportional valve 62 during the arm pushing operation. The control device 8 supplies a command current to the bucket electromagnetic proportional valve 63 during a bucket excavation operation, and supplies a command current to the bucket electromagnetic proportional valve 64 during a bucket dumping operation.
In the present embodiment, cavitation prevention control described below is performed during the arm pulling operation. That is, in the present embodiment, the arm 14 corresponds to the swing portion of the present invention, the arm-pulling operation and the arm-pushing operation correspond to the first operation and the second operation of the present invention, respectively, and the pilot port 42 for the arm-pulling operation and the pilot port 43 for the arm-pushing operation of the arm control valve 41 correspond to the first pilot port and the second pilot port of the present invention, respectively.
During a bucket excavation operation and a bucket dumping operation, the control device 8 supplies a command current proportional to the bucket operation signal Sb to the bucket electromagnetic proportional valve (63 or 64). Further, when the arm pushing operation is performed, the control device 8 supplies a command current proportional to the arm operation signal Sa to the arm electromagnetic proportional valve 62.
On the other hand, during the arm pulling operation, the control device 8 does not necessarily have to supply a command current proportional to the arm operation signal Sa to the arm electromagnetic proportional valve 61.
The control device 8 is electrically connected to the pressure sensor 81. The pressure sensor 81 detects at least the pressure of the hydraulic oil supplied from the main pump 31 to the arm cylinder 22 at the time of the arm pulling operation. In the present embodiment, the pressure sensor 81 is provided in the supply line 32 and detects the discharge pressure Pd of the main pump 31 (the pressure of the hydraulic oil supplied to the arm cylinder 22 during the arm pulling operation and the arm pushing operation). However, pressure sensor 81 may be provided in arm pulling supply pipe 22a to detect the pressure on the inflow side of arm cylinder 22 during the arm pulling operation.
The control device 8 is prestored with a threshold α to be compared with the discharge pressure Pd, and the threshold α is a value at which cavitation may occur on the head side of the arm cylinder 22 if the discharge pressure Pd is lower than this.
When the arm operation device 71 receives the arm pulling operation (when the arm operation device 71 outputs the arm pulling operation signal), if the discharge pressure Pd detected by the pressure sensor 81 is greater than the threshold value α, the control device 8 selects the characteristic Ce shown in fig. 3 and controls the arm solenoid proportional valve 61 so that the secondary pressure output from the arm solenoid proportional valve 61 changes from zero to the maximum value Pm in accordance with the arm operation signal Sa, in other words, the command current proportional to the arm operation signal Sa is supplied to the arm solenoid proportional valve 61.
On the other hand, when the discharge pressure Pd detected by the pressure sensor 81 is smaller than the threshold value α, the control device 8 selects the characteristic Co shown in fig. 3 and controls the arm solenoid proportional valve 61 so that the secondary pressure output from the arm solenoid proportional valve 61 is limited to the set value Ps smaller than the maximum value Pm or less, that is, when the arm operation signal Sa is smaller than the threshold value Sc corresponding to the set value Ps, the secondary pressure output from the arm solenoid proportional valve 61 is changed from zero to the set value Ps in accordance with the arm operation signal Sa, and when the arm operation signal Sa is larger than the threshold value Sc, the secondary pressure output from the arm solenoid proportional valve 61 is maintained at the set value Ps.
Accordingly, As shown in fig. 4, the opening area on the outlet throttle side of the arm control valve 41 is allowed to increase to the maximum value Am when the discharge pressure Pd is greater than the threshold value α, and is allowed to increase only to the predetermined value As. smaller than the maximum value Am when the discharge pressure Pd is smaller than the threshold value α, which is cavitation prevention control, the predetermined value As is the maximum value of the opening area that is allowed to prevent cavitation from occurring on the head side of the arm cylinder 22 under the most severe conditions (when the arm is horizontal away from the cab 16, and the influence of self weight on the rocking is the greatest), and the set value Ps is a value at which the opening area on the outlet throttle side of the arm control valve 41 is set to the predetermined value As.
First, the control device 8 determines whether or not the arm pulling operation is performed (step S1), and when the arm pulling operation is performed (yes in step S1), the control device 8 compares the discharge pressure Pd with the threshold α (step S2), and when the discharge pressure Pd is greater than the threshold α (yes in step S2), the control device 8 selects the characteristic Ce as the secondary pressure of the electromagnetic proportional valve for arm 61 (step S3), and when the discharge pressure Pd is less than the threshold α (no in step S2), the characteristic Co is selected as the secondary pressure of the electromagnetic proportional valve for arm 61 (step S4).
In the drive system 1A configured as described above, when the pressure of the hydraulic oil supplied from the main pump 31 to the arm cylinder 22 is lowered by the gravity acting on the arm 14 so as to accelerate the swing of the arm 14 during the arm pulling operation, the secondary pressure output from the electromagnetic proportional valve 61 for the arm is limited to the set value Ps or less. That is, at this time, the opening area on the outlet throttle side of the arm control valve 41 is limited to the predetermined value As or less. Cavitation can be prevented from occurring in the arm cylinder 22 due to the influence of gravity. Further, compared to the conventional drive system 100 shown in fig. 10, the pilot on-off valve 120 and the pressure reducing valve 130 are not required, and the above-described effects can be obtained by controlling the electromagnetic proportional valve 61 for the arm, so that the drive system 1A can be made to have a simple configuration. In particular, when the arm operating device 71 is an electric joystick as in the present embodiment, no additional equipment is required, and the drive system 1A of the present embodiment can be realized at low cost.
On the other hand, when the discharge pressure Pd is greater than the threshold value α and cavitation is not likely to occur during the arm pulling operation, the opening area on the outlet throttle side of the arm control valve 41 may be increased to the maximum value Am.
However, when the control is performed based only on the characteristic Ce, rather than selecting one of the characteristics Ce and Co at the time of the arm pulling operation As in the present embodiment, the maximum value Am of the opening area on the outlet throttle side of the arm control valve 41 needs to be decreased to the predetermined value As in order to prevent the occurrence of the cavitation. However, in this configuration, when the control lever of the arm control device 71 is fully tilted, the opening area on the outlet throttle side of the arm control valve 41 functions as an orifice, and thus there is a problem that the fuel consumption rate is not good, in a case where cavitation is not likely to occur, that is, in a case where, for example, the ground is excavated and a reaction force is received from the ground. In contrast, in the present embodiment, when cavitation is not likely to occur, the opening area on the outlet throttle side of arm control valve 41 may be increased to a maximum value Am larger than predetermined value As. Therefore, when the control lever of arm control device 71 is fully tilted, the opening area on the outlet throttle side of arm control valve 41 is ensured to be large, and therefore the fuel consumption rate can be improved.
< modification example >
In the above embodiment, the cavitation prevention control is performed only during the arm pulling operation, but may be performed only during the arm pushing operation. In this case, the arm pushing operation and the arm pulling operation correspond to the first operation and the second operation of the present invention, respectively, and the pilot port 43 for the arm pushing operation and the pilot port 42 for the arm pulling operation of the arm control valve 41 correspond to the first pilot port and the second pilot port of the present invention, respectively. In this case, pressure sensor 81 may be provided in arm pushing supply pipe 22b to detect the pressure on the inflow side of arm cylinder 22 during the arm pushing operation.
The cavitation prevention control may be performed during a bucket excavation operation or a bucket dumping operation. Alternatively, the cavitation prevention control may be performed at the time of the arm pulling operation, the time of the arm pushing operation, the time of the bucket excavating operation, and the time of the bucket dumping operation.
Further, a second threshold value α ' smaller than the threshold value α may be set, and when the pressure detected by the pressure sensor 81 is smaller than the second threshold value α ', the secondary pressure output from the electromagnetic proportional valve may be limited to a second set value Ps ' smaller than the set value Ps or less.
In this case, the control device 8 may have the threshold α previously stored as the first threshold, and may have the second threshold β and the third threshold γ previously stored, the second threshold β being a value larger than the first threshold α, and the third threshold γ being a value between the first threshold α and the second threshold β.
First, the control device 8 determines whether or not the arm pulling operation is performed (step S11), and when the arm pulling operation is performed (yes in step S11), the control device 8 measures the time Δ T from when the discharge pressure Pd falls below the second threshold β until the discharge pressure becomes the third threshold γ (step S12), and then compares the measured time Δ T with the reference time Tc (step S13), the reference time Tc being, for example, 0.01 to 0.5 seconds.
When the measured time Δ T is longer than the reference time Tc (yes in step S13), the control device 8 selects the characteristic Ce as the secondary pressure of the electromagnetic proportional valve for the arm 61 (step S14), and controls the electromagnetic proportional valve for the arm 61 so that the secondary pressure output from the electromagnetic proportional valve for the arm 61 changes from zero to the maximum value Pm in accordance with the arm operation signal Sa. Conversely, if the measured time Δ T is smaller than the reference time Tc (no in step S13), the control device 8 selects the characteristic Co as the secondary pressure of the arm electromagnetic proportional valve 61 (step S15), and controls the arm electromagnetic proportional valve 61 such that the secondary pressure output from the arm electromagnetic proportional valve 61 is limited to the set value Ps or less.
After the characteristic Ce is selected, the control device 8 compares the discharge pressure Pd detected by the pressure sensor 81 with the first threshold α (step S16). in other words, in the present embodiment, the discharge pressure Pd is compared with the first threshold α when the measured time Δ T is longer than the reference time Tc.
If the discharge pressure Pd is greater than the first threshold α (yes in step S16), the control device 8 maintains the characteristic Ce until the arm pulling operation is not performed (no in step S17), in other words, maintains the characteristic Ce until the discharge pressure Pd is lower than the first threshold α, on the other hand, if the discharge pressure Pd is less than the threshold α (no in step S16), in other words, if the discharge pressure Pd is lower than the first threshold α, the control device 8 proceeds to step S15 to switch to the characteristic Co.
For example, fig. 7 shows a change over time in the discharge pressure Pd of the main pump 31 when the arm pulling operation is performed from a state in which the arm 14 is horizontal. Fig. 8 shows a temporal change in the discharge pressure Pd of the main pump 31 when the arm pulling operation is performed in a state in which the arm 14 is tilted downward (e.g., 45 degrees). The solid line in fig. 7 and 8 indicates a case where the control according to the flowchart shown in fig. 6 is performed, and the broken line indicates a case where the control based only on the characteristic Ce is performed.
In fig. 7 and 8, the change with time in the discharge pressure Pd during excavation is indicated by a chain line and a two-dot chain line. The chain line indicates a case where the maximum value Am of the opening area on the outlet throttle side of the arm control valve 41 is set to be larger than the predetermined value As when the control according to the flowchart shown in fig. 6 is performed. The two-dot chain line indicates a case where the maximum value Am of the opening area on the outlet throttle side of the arm control valve 41 is set to the predetermined value As when the control based only on the characteristic Ce is performed.
In contrast, in the control shown in fig. 6, the threshold α must be set sufficiently high to prevent the arm 14 from stalling (free fall) even if the first threshold α is set low, so that the arm 14 does not stall even if the deviation or the like is included, in the control shown in fig. 6, the opening area on the outlet throttle side of the arm control valve 41 can be ensured to be large for a long time when the discharge pressure Pd is long from below the second threshold β to the third threshold γ, in other words, the influence of gravity on the arm 14 is small, and thus the range (pump pressure range) in which the pressure on the outlet throttle side during excavation can be reduced can be expanded, and the discharge pressure of the arm 22 during excavation can be used instead of the discharge pressure Pd in the control shown in fig. 6.
(second embodiment)
Fig. 9 shows a hydraulic shovel drive system 1B according to a second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted.
In the present embodiment, each of the arm operation device 71 and the bucket operation device 72 is a pilot operation valve that outputs a pilot pressure as an operation signal (Sa or Sb). In the present embodiment, cavitation prevention control is performed during the arm pulling operation and the bucket excavating operation. Therefore, the arm control device 71 is directly connected to the pilot port 43 for the arm pushing operation of the arm control valve 41 through the pilot pipe line 52, but is connected to the pilot port 42 for the arm pulling operation via the electromagnetic proportional valve 65. More specifically, the electromagnetic proportional valve 65 is connected to the pilot port 42 and the arm operating device 71 through the pilot conduits 51 and 55.
Similarly, the bucket operating device 72 is directly connected to the pilot port 46 for bucket dumping operation of the bucket control valve 44 via the pilot line 54, but is connected to the pilot port 45 for bucket excavating operation via the electromagnetic proportional valve 66. More specifically, the electromagnetic proportional valve 66 is connected to the pilot port 45 and the bucket operating device 72 through the pilot lines 53 and 56.
The electromagnetic proportional valves 65, 66 are respectively of an inverse proportional type in which the output secondary pressure and the command current exhibit a negative correlation. That is, when the command current is not supplied to the electromagnetic proportional valves 65 and 66, the secondary pressure output from the electromagnetic proportional valves 65 and 66 is equal to the pilot pressure output from the arm operation device 71 and the bucket operation device 72. However, the electromagnetic proportional valves 65 and 66 may be of a proportional type.
In the present embodiment, the pilot pressure (arm operation signal Sa) output by the arm operation device 71 when receiving the arm pulling operation is detected by the pressure sensor 82, and the pilot pressure (bucket operation signal Sb) output by the bucket operation device 72 when receiving the bucket excavating operation is detected by the pressure sensor 83. The pilot pressure detected by the pressure sensors 82 and 83 is input to the control device 8.
In the present embodiment, when the arm operation device 71 receives the arm pulling operation, if the discharge pressure Pd detected by the pressure sensor 81 is greater than the threshold value α, the control device 8 controls the electromagnetic proportional valve 65 so that the secondary pressure output from the electromagnetic proportional valve 65 changes from zero to the maximum value Pm in response to the arm operation signal Sa, and specifically, the control device 8 does not supply the command current to the electromagnetic proportional valve 65.
Conversely, when the discharge pressure Pd is less than the threshold value α, the control device 8 controls the electromagnetic proportional valve 65 so that the secondary pressure output from the electromagnetic proportional valve 65 is limited to the set value Ps that is less than the maximum value Pm or less, and specifically, when the arm operation signal Sa is greater than the threshold value Sc, the control device 8 supplies the command current to the electromagnetic proportional valve 65 so that the secondary pressure of the electromagnetic proportional valve 65 is maintained at the set value Ps.
Similarly, when the discharge pressure Pd detected by the pressure sensor 81 is greater than the threshold value α when the bucket operating device 72 receives a bucket excavating operation, the control device 8 controls the electromagnetic proportional valve 66 so that the secondary pressure output from the electromagnetic proportional valve 66 changes from zero to the maximum value Pm in accordance with the bucket operating signal Sb, and specifically, the control device 8 does not supply a command current to the electromagnetic proportional valve 66.
Conversely, when the discharge pressure Pd is less than the threshold value α, the control device 8 controls the electromagnetic proportional valve 66 so that the secondary pressure output from the electromagnetic proportional valve 66 is limited to the set value Ps that is less than the maximum value Pm or less, and specifically, when the bucket operation signal Sb is greater than the threshold value Sc, the control device 8 supplies the command current to the electromagnetic proportional valve 66 so that the secondary pressure of the electromagnetic proportional valve 66 is maintained at the set value Ps.
The same effects as those of the first embodiment can be obtained in this embodiment. Further, although not shown, when the arm operating device 71 is connected to the pilot port 43 for the arm pushing operation of the arm control valve 41 via the electromagnetic proportional valve, cavitation prevention control can be performed at the time of the arm pushing operation. Similarly, when the bucket operating device 72 is connected to the pilot port 46 for bucket dumping operation of the bucket control valve 44 via the electromagnetic proportional valve, cavitation prevention control can be performed at the time of bucket operation.
(other embodiment)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, the hydraulic excavator 10 on which the drive system (1A or 1B) is mounted does not necessarily have to be of a self-propelled type. For example, when the hydraulic excavator 10 is loaded on a ship, the revolving structure 12 may be supported by the hull so as to be pivotable.
Description of the symbols:
1A, 1B hydraulic shovel drive systems;
10 oil hydraulic excavators;
14 an arm (swing portion);
15 a bucket (swing portion);
22a bucket rod cylinder;
23a bucket cylinder;
41 bucket rod control valves;
42 a second pilot port;
43 a first pilot port;
44 a bucket control valve;
45 a second pilot port;
46 a first pilot port;
61-64 electromagnetic proportional valves;
71 a dipper handle operating device;
72 a bucket operating device;
8 a control device;
81-83 pressure sensors.
Claims (2)
1. A hydraulic shovel drive system is characterized in that,
the disclosed device is provided with:
a cylinder configured to swing a swing portion that is a boom or a bucket;
a control valve that controls supply and discharge of hydraulic oil to and from the cylinder, and that has a first pilot port for a first operation of swinging the swing portion in one direction and a second pilot port for a second operation of swinging the swing portion in a direction opposite to the one direction;
an operation device including an operation lever that outputs an operation signal corresponding to a tilt angle of the operation lever when receiving the first operation;
an electromagnetic proportional valve connected to the first pilot port;
a pressure sensor that detects at least a pressure of the working oil supplied from the pump to the cylinder at the first operation; and
a control device for controlling the electromagnetic proportional valve;
when the operation device receives the first operation, the control device controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve changes from zero to a maximum value in accordance with the operation signal when the pressure detected by the pressure sensor is greater than a threshold value, and controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve is limited to a set value smaller than the maximum value or less when the pressure detected by the pressure sensor is smaller than the threshold value.
2. The hydraulic shovel drive system according to claim 1,
the threshold is a first threshold;
the control device measures a time from a time when the pressure detected by the pressure sensor is lower than a second threshold value that is larger than the first threshold value to a time when the pressure becomes a third threshold value between the first threshold value and the second threshold value, controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve changes from zero to a maximum value in accordance with the operation signal if the measured time is larger than a reference time, and controls the electromagnetic proportional valve such that the secondary pressure output from the electromagnetic proportional valve is limited to the set value or less if the measured time is smaller than the reference time;
the control device compares the first threshold value with the pressure detected by the pressure sensor when the measured time is greater than the reference time.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017-201748 | 2017-10-18 | ||
| JP2017201748A JP6936690B2 (en) | 2017-10-18 | 2017-10-18 | Hydraulic excavator drive system |
| PCT/JP2018/037976 WO2019078091A1 (en) | 2017-10-18 | 2018-10-11 | Hydraulic shovel drive system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111148906A true CN111148906A (en) | 2020-05-12 |
| CN111148906B CN111148906B (en) | 2022-03-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201880064787.4A Active CN111148906B (en) | 2017-10-18 | 2018-10-11 | Hydraulic shovel drive system |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP6936690B2 (en) |
| CN (1) | CN111148906B (en) |
| WO (1) | WO2019078091A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024000942A1 (en) * | 2022-06-30 | 2024-01-04 | 中联重科土方机械有限公司 | Positive flow excavator and control method and control device therefor, and controller |
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Also Published As
| Publication number | Publication date |
|---|---|
| CN111148906B (en) | 2022-03-18 |
| JP2019074171A (en) | 2019-05-16 |
| JP6936690B2 (en) | 2021-09-22 |
| WO2019078091A1 (en) | 2019-04-25 |
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