JP3757178B2 - Drive control device for work vehicle - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a drive control device for a work vehicle, and more specifically, a swivel base provided on a swivelable body so as to be capable of swiveling, a boom provided on the swivel base so as to be able to move up and down, and a tip of the boom The present invention relates to a drive control device for a work vehicle that controls the drive of an arm that can bend and extend.
[0002]
[Prior art]
The work vehicle configured in this way is often used when excavating the ground or moving the excavated soil or the like, and has a bucket pivotably connected to the tip of the arm. There is something that was done.
[0003]
A driving cabin is provided on the swivel of such a working vehicle, and an operating device capable of driving the boom, arm and bucket while an operator is sitting on a chair is provided in the driving cabin. The operating device includes a first operating lever for rotating the swivel base and bending and extending the arm, and a second operating lever for raising and lowering the boom and swinging the bucket. The first operating lever and the second operating lever Is configured to be tiltable in the front-rear and left-right directions. When the first operating lever is tilted forward in the front-rear direction, the arm bends and extends upward, and when the first operating lever is tilted back in the front-rear direction, the arm bends and extends downward. When the tilting operation is performed to the left in the left-right direction, the swivel is turned left, and when the first operating lever is tilted to the right in the left-right direction, the swivel is turned right.
[0004]
In addition, the first operation lever and the second operation lever can be tilted in an oblique direction. For example, when the first operation lever is tilted to the right front side, the swivel turns right and the arm The operation device is configured to allow so-called combined operation so that the robot can bend and extend upward.
[0005]
Here, a drive control device that controls the drive of the swivel base, the boom, and the arm according to the operation by the operation device will be described with reference to FIG. FIG. 3 shows the configuration of the drive control device. As shown in FIG. 3, the drive control device includes a turning motor 12 for turning the turntable, a boom cylinder 31 for raising and lowering the boom, and an arm for bending and extending the arm. Swing drive control that is provided corresponding to each of the cylinder 33, the variable displacement hydraulic pump P, the swing motor 12, the boom cylinder 31, and the arm cylinder 33 and that controls the supply and discharge of oil supplied from the hydraulic pump P. A valve 41, a boom drive control valve 51, and an arm drive control valve 61 are provided.
[0006]
The turning drive control valve 41, the boom drive control valve 51, and the arm drive control valve 61 are connected to the hydraulic pump P through a pump pressure oil passage 70. The swing drive control valve 41 is selectively connected to the swing motor 12 via a first oil passage 42 that supplies hydraulic pressure, and the boom drive control valve 51 is connected to the bottom chamber 31a of the boom cylinder 31 via the second oil passage 52. The arm drive control valve 61 is configured to be selectively connected to the bottom chamber 33 a and the rod chamber 33 b of the arm cylinder 33 via the third oil passage 62. A first pilot oil passage 44, a second pilot oil passage 54, and a third pilot oil passage 64 communicate with the first oil passage 42, the second oil passage 52, and the third oil passage 62, respectively. 44, 54 and 64 are connected to the regulator valve R via three shuttle valves 45, 55 and 65. The regulator valve R is selected by the three shuttle valves 45, 55, 65 and has the highest hydraulic pressure (hereinafter referred to as “maximum load pressure”) among the hydraulic pressures in the pilot oil passages 44, 54, 64. The pilot pressure acts via a regulator pilot oil passage 71. The regulator valve R is applied to the swash plate S of the hydraulic pump P according to the magnitude of the maximum load pressure so that the differential pressure between the pump pressure in the pump pressure oil passage 70 and the maximum load pressure described above becomes a predetermined constant value. The connected capacity cylinder 72 is expanded and contracted to change the inclination of the swash plate S to change the capacity of the hydraulic pump P.
[0007]
A first pressure compensation valve 47, a second pressure compensation valve 57, and a third pressure compensation valve 67 are provided in the first oil passage 42, the second oil passage 52, and the third oil passage 62, respectively. The compensation valve 47, 57, 67 acts as a pilot pressure through a pressure compensation pilot oil passage 79 where the aforementioned maximum load pressure branches from the regulator pilot oil passage 71. These pressure compensation valves 47, 57, and 67 are provided with movable spool valves. The hydraulic pressure flowing into the pressure compensation valve acts on one side of the spool valve, and the pressure compensation valve 47 on the other side of the spool valve. , 57 and 67, the spring pressure of the spring 74 and the pilot pressure act, and the spool valve moves by the pressure of these oil pressures, and the first oil passage 42, the second oil passage 52 and the third oil passage 62 are moved. Are configured to communicate and block.
[0008]
According to the drive control apparatus configured as described above, when a load is applied to at least one of the swing motor 12, the boom cylinder 31, and the arm cylinder 33 (hereinafter collectively referred to as "actuator"), the drive control apparatus is activated. The hydraulic pump P discharges only the required flow rate so that the actuator with the largest load applied can be driven, and the maximum load pressure corresponding to the largest load is used as the pilot pressure, the swing drive control valve 41, the boom It acts on each of the drive control valve 51 and the arm drive control valve 61. For this reason, when a large load is applied to the boom in a state where the operating device is operated and the actuator is performing a combined operation, for example, the swivel is swiveling and the boom is lifting, the hydraulic pump P The capacity is increased, and oil is further discharged from the hydraulic pump P by a necessary flow rate so that the boom cylinder 31 can be driven against a large load.
[0009]
Further, the oil discharged from the hydraulic pump P increases the hydraulic pressure in the second oil passage 52 ′ upstream from the second pressure compensation control valve 57, and the spool valve in the second pressure compensation control valve 57 is turned on. The valve is moved in the valve opening direction, and the second pressure compensation control valve 57 is opened. For this reason, the second oil passage 52 ′ is in a communicating state, and the pressurized oil is supplied to the bottom chamber 31 a of the boom cylinder 31 via the boom drive control valve 51, and the boom cylinder 31 extends and resists the load. . On the other hand, the oil discharged from the hydraulic pump P increases the hydraulic pressure in the first oil passage 42 ′ upstream from the first pressure compensation control valve 47, and the spool valve in the first pressure compensation control valve 47 is The valve is moved in the valve opening direction, and the first pressure compensation control valve 47 is opened. For this reason, the first oil passage 42 ′ is in a communicating state, the pressurized oil is supplied to the turning motor 12 via the turning drive control valve 41, the turning motor 12 is rotated, and the turning table is turned.
[0010]
The oil discharged from the hydraulic pump P in this way is supplied to the first pressure compensation control valve 47 and the second pressure compensation control valve 57, but the second pressure compensation control is performed in the second oil passage 52 connected to the boom cylinder 31. Assuming the case where the valve 57 is not disposed, when the load acting on the boom cylinder 31 is smaller than the maximum load pressure for opening the first pressure compensation control valve 47, most of the oil discharged from the hydraulic pump P is An attempt is made to flow into the boom drive control valve 51. As a result, the pressure increase speed of the oil in the first oil passage 42 ′ upstream from the first pressure compensation control valve 47 becomes slow, and the opening area of the first pressure compensation control valve 47 does not increase. As a result, the swing motor 12 rotation speed becomes slow. Therefore, a second pressure compensation control valve 57 is provided in the second oil passage 52, and the hydraulic pressure in the second oil passage 52 'upstream of the second pressure compensation control valve 57 is maintained at a predetermined pressure exceeding the maximum load pressure. Thus, the hydraulic pressure of the oil that is about to flow into the first pressure compensation control valve 47 can be increased, and the first pressure compensation control valve 47 is opened with a large opening area. For this reason, a hydraulic pressure of a predetermined pressure exceeding the maximum load pressure can be supplied to the swing motor 12, and a decrease in the rotation speed of the swing motor 12 is prevented. The first oil pressure control valve 47 having the same function as the second pressure compensation control valve 57 and the first oil passage 42 connected to the swing motor 12 and the third oil passage 62 connected to the arm cylinder 33 according to the above-described reason and the second oil pressure control valve 47 are provided. A three pressure compensation control valve 67 is provided.
[0011]
[Problems to be solved by the invention]
However, since the first pressure compensation control valve 47 is configured so that the maximum load pressure acts as a pilot pressure, when the swivel is swung and the boom is raised and lowered, a large load acts on the boom and the relief is performed. When an allowable maximum load pressure that is a predetermined lower pressure than the pressure acts on the first pressure compensation control valve 47, the hydraulic pressure in the first oil passage 42 downstream of the first pressure compensation valve 47 is caused by the first pressure compensation valve 47. The hydraulic pressure is made smaller than the relief pressure and slightly larger than the total pressure of the allowable maximum load pressure and the spring pressure of the spring 74 of the first pressure compensation valve 47. As a result, the spool valve of the first pressure compensation control valve 47 is in a state of being pressed against each other, and the first pressure compensation control valve 47 is slightly opened. For this reason, the amount of oil supplied to the turning motor 12 decreases, and there arises a problem that the turning speed of the turntable becomes slow.
[0012]
In addition, when the arm is bent and extended while the swivel is swiveling, if a large load acts on the arm, the swivel speed of the swivel decreases as in the case where a large load acts on the boom described above. Problems arise.
[0013]
The present invention has been made in view of such a problem, and the influence of the load pressure acting on the boom or the arm when the swiveling motion of the swivel base and the swinging motion of the boom or the bending and extending motion of the arm are performed. Accordingly, an object of the present invention is to provide a work vehicle drive control device configured so that the turning speed of the turntable does not become slow.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, a drive control device for a work vehicle according to the present invention includes a swivel provided on a vehicle body (for example, a traveling carriage 7 in the embodiment) so as to be turnable, a turn motor for turning the turntable, A boom that can be raised and lowered on the swivel base, a boom cylinder that raises and lowers the boom, an arm that can be bent and extended vertically at the tip of the boom, and an arm cylinder that flexes and extends the arm. A drive control device for a work vehicle (for example, the backhoe 1 in the embodiment), which is provided corresponding to each of a variable displacement hydraulic pump, a swing motor, a boom cylinder, and an arm cylinder. Swivel drive control valve, boom drive control valve and arm drive control valve for controlling supply / discharge of supplied oil, hydraulic pump, swing drive control valve, boom A pump pressure oil passage connecting the dynamic control valve and the arm drive control valve, a first oil passage connecting the swing drive control valve and the swing motor to supply hydraulic pressure, a boom drive control valve and a rod chamber of the boom cylinder or The second oil passage connecting the bottom chamber, the third oil passage connecting the arm drive control valve and the bottom chamber or rod chamber of the arm cylinder, the first oil passage, the second oil passage, and the third oil passage, respectively. The first pilot oil passage, the second pilot oil passage, and the third pilot oil passage that are connected to each other, and the first pilot oil passage, the second pilot oil passage, and the third pilot oil passage that communicate with each other. The hydraulic pressure of the pump pressure oil path and the maximum load pressure are adjusted by changing the capacity of the hydraulic pump according to the highest load pressure of the highest hydraulic pressure and adjusting the amount of oil supplied from the hydraulic pump. Is provided in each of the oil supply amount adjusting means (for example, the capacity cylinder 72 and the regulator valve R in the embodiment), the first oil passage, the second oil passage, and the third oil passage to make the predetermined constant value. The highest hydraulic pressure of the pilot oil passage, the second pilot oil passage, and the third pilot oil passage is received as the pilot pressure, and the oil supplied to the swing motor, boom cylinder and arm cylinder is the highest load pressure. The first pressure compensation valve, the second pressure compensation valve, the third pressure compensation valve, and the pump pressure oil passage, which are set to a predetermined pressure exceeding the pressure, are provided in the pump pressure oil passage so that the hydraulic pressure of the pump pressure oil passage does not exceed the predetermined relief pressure. And a relief valve (for example, the relief valve 77 in the embodiment) that is provided in the first pilot oil passage, and has an allowable maximum load pressure that is a predetermined lower pressure than the relief pressure. When receiving as a pilot oil passage communicating means (for example, a pilot pressure switching valve 80 in the embodiment) for communicating the first pilot oil passage with the first pressure compensation valve. When the hydraulic pressure acting on the swing motor is received through the first pilot oil passage by the communication means, the hydraulic pressure of the oil supplied from the swing drive control valve to the swing motor is set to a predetermined hydraulic pressure exceeding the hydraulic pressure. Configured as follows.
[0015]
According to the drive control device having the above-described configuration, the pilot oil passage communicating means for communicating the first pilot oil passage with the first pressure compensation valve is provided, so that when the swivel is turning, the boom or When a large load acts on the arm, the allowable maximum load pressure corresponding to this large load acts on the pilot oil passage communication means, and the pilot oil passage communication means blocks the action of the allowable maximum load pressure on the first pressure compensation valve. The first pilot oil passage is communicated with the first pressure compensation valve. For this reason, the first pressure compensation valve is opened with a large opening area by the hydraulic pressure supplied from the hydraulic pump to the first pressure compensation valve and boosted. As a result, there is a situation in which hydraulic oil having a predetermined pressure exceeding the hydraulic pressure is supplied to the swing motor in a state where the amount of oil is large, the rotary motor rotates at a desired rotational speed, and the rotational speed of the swivel base decreases. Can be prevented.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. This embodiment shows a mode of a backhoe used when excavating the ground or moving excavated soil or the like. First, before explaining the drive control device according to the present invention, a backhoe equipped with this drive control device will be explained. As shown in FIG. 1, the backhoe 1 includes a traveling carriage 7 that includes a traveling device 5 having a pair of left and right crawler belts 3, a swivel base 11 that is turnable on the traveling carriage 7, A power shovel device 20 pivotally connected to the front portion and an operator cabin 15 provided on the upper part of the swivel base 11 are configured.
[0017]
The swivel base 11 can be swiveled by a swivel motor 12 shown in FIG. The power shovel device 20 includes a boom 25 whose base end is pivotally connected to the lower front end of the swivel base 11 and swingable up and down, and an arm 27 pivotally connected to the tip of the boom 25 and swingable up and down. And a bucket 29 pivotally pivoted up and down at the tip of the arm 27. The boom 25 can be raised and lowered by a boom cylinder 31 pivotally connected between the lower front end of the swivel base 11 and the lower surface of the boom 25, and the arm 27 is pivoted between the upper surface of the boom 25 and the base of the arm 27. 33 can bend and extend, and the bucket 29 can swing up and down by a bucket cylinder 35 pivotally connected between the upper surface of the arm 27 and the base of the bucket 29.
[0018]
In the operator cabin 15, an operator seat 17 is provided on the side of the power shovel device 20 where an operator (not shown) faces. A pair of traveling operation levers 19 for operating the left and right crawler belts 3 are provided at the end of the bottom plate 16 in the operator cabin 15 and on the front side in the front-rear direction (the power shovel device 20 side) with respect to the operator seat 17. . On the left and right sides of the operator seat 17 are arranged operating devices 21 for operating the drive of the power shovel device 20. The operating device 21 includes a left operating lever 21a and a right operating lever 21b, and these operating levers 21a and 21b are configured to be tiltable forward / backward and left / right.
[0019]
When the left operating lever 21a is tilted forward in the front-rear direction, the arm 27 bends and extends upward, and when the left operating lever 21a is tilted back in the front-rear direction, the arm 27 bends and extends downward. When the lever 21a is tilted to the left in the left-right direction, the swivel base 11 turns left, and when the left operation lever 21a is tilted to the right in the left-right direction, the swivel base 11 turns right. . On the other hand, when the right operating lever 21b is tilted forward in the front-rear direction, the boom 25 is tilted down, and when the right operating lever 21b is tilted back in the front-rear direction, the boom 25 is lifted up, and the right operating lever The bucket 29 is configured to excavate when the left side 21b is tilted to the left in the left-right direction, and the bucket 29 is dumped when the right control lever 21b is tilted to the right in the left-right direction.
[0020]
Further, the operating device 21 is configured so that the left operating lever 21a and the right operating lever 21b can be tilted in an oblique direction. For example, when the left operating lever 21a is tilted to the right front side, the swivel base 11 is rotated clockwise. The arm 27 is configured to rotate and bend and extend upward.
[0021]
The power shovel device 20 described above is connected to a drive control device that controls its operation in response to an operation signal from the operation device 21. As shown in FIG. 2, the drive control device 40 includes a swing motor 12, a boom cylinder 31, an arm cylinder 33, a variable displacement hydraulic pump P that changes the capacity by changing the inclination of the swash plate S, and a swing motor. 12, a swing drive control valve 41, a boom drive control valve 51, and an arm drive control valve 61, which are provided corresponding to each of the boom cylinder 31 and the arm cylinder 33 and perform supply / discharge control of hydraulic oil supplied from the hydraulic pump P. And is configured.
[0022]
The turning drive control valve 41, the boom drive control valve 51, and the arm drive control valve 61 are 7-port 3-position direction switching valves, and are connected to the hydraulic pump P via the pump pressure oil passage 70, respectively. The turning drive control valve 41 is connected to a first oil passage 42 for supplying hydraulic pressure, and the first oil passage 42 is selected as a pair of turning communication oil passages 43 and 43 ′ communicated between the turning motor 12 and the turning drive control valve 41. Connected. The boom drive control valve 51 is connected to a second oil passage 52 for supplying hydraulic pressure, and the second oil passage 52 is connected to a pair of boom communication oil passages 53 and 53 ′ communicated between the bottom chamber 31 a and the rod chamber 31 b of the boom cylinder 31. Is connected selectively. The arm drive control valve 61 is connected to a third oil passage 62 for supplying hydraulic pressure, and the third oil passage 62 is connected to a pair of arm communication oil passages 63, 63 'communicated between the bottom chamber 33a and the rod chamber 33b of the arm cylinder 33. Is connected selectively.
[0023]
A first pilot oil passage 44, a second pilot oil passage 54, and a third pilot oil passage 64 communicate with each of the first oil passage 42, the second oil passage 52, and the third oil passage 62. The first pilot oil passage 44 is connected to the third shuttle valve 65 connected to the third pilot oil passage 64 via the first shuttle valve 45 and the first communication pilot oil passage 46, and the second pilot oil passage 54 is connected to the second shuttle oil passage 54. The first pilot valve 45 is connected to the first shuttle valve 45 via the valve 55 and the second communication pilot oil passage 56, and the third pilot oil passage 64 is connected to the third shuttle valve 65 and the third communication pilot oil passage 66. The third communication pilot oil passage 66 is connected to a regulator pilot oil passage 71 connected to a regulator valve R that controls the inclination of the swash plate S of the hydraulic pump P.
[0024]
The first shuttle valve 45, the second shuttle valve 55, and the third shuttle valve 65 are configured to guide the higher hydraulic pressure among the hydraulic pressures acting on the first shuttle valve 45, the second shuttle valve 55, and the third shuttle valve 65 to the communication pilot oil passages 46, 56, and 66. Therefore, the regulator valve R has the highest hydraulic pressure (hereinafter referred to as “maximum load pressure”) among the hydraulic pressures in the three pilot oil passages 44, 54, 64 selected by the three shuttle valves 45, 55, 65. Will act as a pilot pressure. The regulator valve R is applied to the swash plate S of the hydraulic pump P according to the magnitude of the maximum load pressure so that the differential pressure between the pump pressure in the pump pressure oil passage 70 and the maximum load pressure described above becomes a predetermined constant value. The expansion / contraction motion of the connected capacity cylinder 72 is controlled to change the inclination of the swash plate S to change the capacity of the hydraulic pump P. Note that. The rotation speed of the hydraulic pump P is constant, and the amount of oil discharged from the hydraulic pump P changes by changing the inclination of the swash plate S.
[0025]
A first pressure compensation valve 47, a second pressure compensation valve 57, and a third pressure compensation valve 67 are provided in each of the first oil passage 42, the second oil passage 52, and the third oil passage 62. These pressure compensating valves 47, 57 and 67 are 2-port 2-position shut-off valves with a built-in throttle 73, and are movably arranged to open and close an opening (not shown) formed therein. A spool valve (not shown) is provided. In these pressure compensation valves 47, 57 and 67, the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump P acts on one end of the spool valve, and a spring 74 provided in the pressure compensation valves 47, 57 and 67. The total pressure of the spring pressure and the maximum load pressure acts on the other end of the spool valve, and when the operating oil pressure is larger than the total pressure, the spool valve moves to open the opening, and the oil passage 42, 52 and 62 are communicated, and when the hydraulic pressure is lower than the total pressure, the spool valve moves to close the opening and shut off the oil passages 42, 52 and 62. Since the opening has a predetermined area, when the pressure difference between the working hydraulic pressure and the total pressure exceeds a predetermined value, all of the openings are opened, and all of the openings are Closed state.
[0026]
A pressure compensation pilot oil passage 79 is connected to the first pressure compensation valve 47, and a pilot pressure switching valve 80 straddling these oil passages is provided in the pressure compensation pilot oil passage 79 and the first pilot oil passage 44. ing. The pilot pressure switching valve 80 is a 4-port 2-position direction switching valve. When the pilot pressure switching valve 80 receives an allowable maximum load pressure that is lower than the relief pressure from the pressure compensation pilot oil passage 79, the first pilot oil passage 44 is changed to the first one. When the pressure compensation valve 47 is communicated and a maximum load pressure smaller than the permissible maximum load pressure is received, the pressure compensation connected to the first pressure compensation valve 47 so that the maximum load pressure acts on the first pressure compensation valve 47. The pilot oil passage 79 has a function of communicating. A throttle valve 84 is provided in a branch pilot oil passage 81 branched from the pressure compensation pilot oil passage 79 and connected to the pilot pressure switching valve 80.
[0027]
A pressure compensation pilot oil passage 79 is connected to the second pressure compensation valve 57 and the third pressure compensation valve 67, and the above-described maximum load pressure is passed through the pressure compensation pilot oil passage 79 to the second pressure compensation valve 57 and the third pressure compensation valve 79. Acts on the valve 67. These pressure compensation valves 47, 57, 67 are connected to a discharge oil passage 75 communicating with the tank T, and a relief oil passage 86 is connected between the discharge oil passage 75 and the pump pressure oil passage 70. A relief valve 77 is provided to prevent the hydraulic pressure in the pump pressure oil passage 70 from exceeding a predetermined relief pressure.
[0028]
Next, the operation of the drive control device 40 will be described in the case where the turning motor 12 is driven to rotate. The hydraulic pump P is set to be in a state where it can be driven to rotate by receiving a driving force from an engine (not shown). First, when the left operation lever 21a shown in FIG. 1 is operated so that the swivel base 11 turns, the hydraulic oil discharged from the hydraulic pump P passes through the pump pressure oil passage 70 as shown in FIG. The rotation drive control valve 41 is supplied. The hydraulic oil supplied to the turning drive control valve 41 is supplied to the turning motor 12 through the first oil passage 42 and one turning communication oil passage 43. More specifically, when the swing drive control valve 41 is operated so that the hydraulic oil is supplied to the swing motor 12, the hydraulic oil discharged from the hydraulic pump P is passed through the swing drive control valve 41 to the first pressure compensation valve 47. To be supplied. When the hydraulic oil supplied to the first pressure compensation valve 47 becomes larger than the total pressure of the pilot pressure and the spring pressure acting on the first pressure compensation valve 47, the first pressure compensation valve 47 opens, and as a result, the hydraulic pressure The hydraulic oil from the pump P is supplied to the turning motor 12 through the first oil passage 42 and one turning communication oil passage 43. Further, the hydraulic oil in the other swirl communication oil passage 43 ′ connected to the swivel motor 12 is discharged to the tank T through the swivel drive control valve 41 and the discharge oil passage 75, and the swivel motor 12 is rotationally driven.
[0029]
Here, the hydraulic pressure of the first oil passage 42 that supplies hydraulic oil to the turning motor 12 is transmitted to the first pilot oil passage 44, and this hydraulic pressure (hereinafter referred to as “maximum”) is transmitted via the first shuttle valve 45 and the third shuttle valve 65. "Load pressure") acts as a pilot pressure on the regulator valve R via the regulator pilot oil passage 71. Further, the hydraulic pressure in the pump pressure oil passage 70 acts on the regulator valve R as a pilot pressure via the pump pressure pilot oil passage 76.
[0030]
For this reason, the regulator valve R expands and contracts the displacement cylinder 72 so that the hydraulic pressure in the pump pressure oil passage 70 becomes a hydraulic pressure exceeding the maximum load pressure and the total pressure of the spring pressure of the spring 87 of the regulator valve R. As a result, a necessary flow rate capable of rotationally driving the swing motor 12 against the load acting on the swing motor 12 is discharged from the hydraulic pump P.
[0031]
Here, a load corresponding to a predetermined allowable maximum load pressure lower than the relief pressure at which the relief valve 77 shown in FIG. 2 opens in the boom 25 shown in FIG. 1 (hereinafter referred to as “allowable maximum load”). Considering the case where the swivel base 11 shown in FIG. When an allowable maximum load is applied to the boom 25 shown in FIG. 1, an allowable maximum load pressure that is the maximum load pressure is applied to the regulator valve R, and the regulator valve R expands and contracts the capacity cylinder 72 to swash plate of the hydraulic pump P. Change the slope of S. As a result, hydraulic oil is further discharged from the hydraulic pump P by a necessary flow rate so that the boom cylinder 31 can expand and contract against the allowable maximum load pressure.
[0032]
Assuming that the pressure compensation pilot oil passage 79 is directly connected to the first pressure compensation valve 47 as shown in FIG. 3, the allowable maximum load pressure is the maximum load pressure in the first pressure compensation valve 47. Will act as. The allowable maximum load pressure is a hydraulic pressure close to the relief pressure, and the hydraulic pressure in the first oil passage 42 on the downstream side of the first pressure compensation valve 47 does not exceed the relief pressure. The hydraulic pressure acting on the control valve 41 is slightly higher than the sum of the allowable maximum load pressure and the spring pressure, and the spool valve (not shown) in the first pressure compensation valve 47 is in a state of being pressed against each other. The first pressure compensation valve 47 is slightly opened. As a result, the amount of hydraulic oil supplied to the turning motor 12 decreases, and the turning speed of the turning motor 12 decreases.
[0033]
However, in the drive control device 40 according to the present invention, as shown in FIG. 2, when the allowable maximum load pressure is applied to the pilot pressure switching valve 80, the pilot pressure switching valve 80 causes the first pilot oil passage 44 to pass through the first pressure compensation. Connect to the valve. For this reason, the hydraulic pressure (swing load pressure) of the swing communication oil passage 43 acts on the first pressure compensating valve via the first pilot oil passage 44.
[0034]
On the other hand, since the hydraulic pressure of the first oil passage 42 connected to the downstream side of the first pressure compensation valve 47 can be increased to the vicinity of the relief pressure, the hydraulic oil supplied from the first pressure compensation valve 47 to the turning drive control valve 41 is reduced. The hydraulic pressure is larger than the total pressure of the turning load pressure and the spring pressure of the spring 74. For this reason, the spool valve (not shown) of the first pressure compensation valve 47 is pushed out and opens in a substantially maximum state, thereby increasing the amount of hydraulic oil supplied to the turning communication oil passage 43. it can. As a result, the operating hydraulic pressure acting on the swing motor 12 can be quickly increased to the desired hydraulic pressure, and a situation in which the swing speed of the swivel base 11 shown in FIG. 1 is reduced can be prevented. It should be noted that the maximum allowable load pressure does not suddenly act on the pilot pressure switching valve 80 by the throttle valve 84 provided in the branch pilot oil passage 81, and a pilot pressure that gradually increases acts on the pilot pressure switching valve 80. The allowable maximum load pressure acts on the pilot pressure switching valve 80 with a time difference. For this reason, the pilot pressure switching valve 80 is gradually switched to prevent a situation in which the turning load pressure suddenly acts on the first pressure compensation valve 47 and the rotation speed of the turning motor 12 changes suddenly.
[0035]
In the above-described embodiment, the case where the swivel base 11 is swung and the boom 25 is lifted has been described. However, the case where the arm 27 is bent and extended is the same as the case where the boom 25 is lifted. An effect can be obtained.
[0036]
【The invention's effect】
As described above, according to the drive control device of the present invention, the pilot oil passage communicating means for communicating the first pilot oil passage with the first pressure compensation valve is provided, so that the swivel is swung. When a large load is applied to the boom or the arm, the maximum allowable load pressure corresponding to this large load is applied to the pilot oil passage communication means, and the pilot oil passage communication means is the allowable maximum load to the first pressure compensation valve. The action of pressure is cut off, and the first pilot oil passage is communicated with the first pressure compensation valve. For this reason, the first pressure compensation valve is opened with a large opening area due to the hydraulic pressure supplied from the hydraulic pump to the first pressure compensation valve and boosted. As a result, there is a situation in which hydraulic oil having a predetermined pressure exceeding the hydraulic pressure is supplied to the swing motor in a state where the amount of oil is large and the swing motor rotates at a desired rotational speed, and the rotational speed of the swivel base decreases. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a perspective view of a backhoe equipped with a drive control device according to the present invention.
FIG. 2 is a hydraulic circuit diagram of a drive control device according to the present invention.
FIG. 3 is a hydraulic circuit diagram of a conventional drive control device.
[Explanation of symbols]
1 Backhoe (work vehicle)
7 Traveling cart (body)
DESCRIPTION OF SYMBOLS 11 Swivel base 12 Swivel motor 25 Boom 27 Arm 31 Boom cylinder 31a, 33a Bottom chamber 31b, 33b Rod chamber 33 Arm cylinder 40 Drive control apparatus 41 Swivel drive control valve 42 1st oil path 44 1st pilot oil path 47 1st pressure Compensation valve 51 Boom drive control valve 52 Second oil passage 54 Second pilot oil passage 57 Second pressure compensation valve 61 Arm drive control valve 62 Third oil passage 64 Third pilot oil passage 67 Third pressure compensation valve 70 Pump pressure oil Path 72 Capacity cylinder (Oil supply amount adjusting means)
77 Relief valve (Relief valve)
80 Pilot pressure switching valve (Pilot oil passage communication means)
P Hydraulic pump R Regulator valve (Oil supply amount adjusting means)

Claims (1)

A swivel base that is swingably provided on a vehicle body, a swing motor that swings the swivel base, a boom that is swingable on the swivel base, a boom cylinder that moves the boom up and down, and the boom A work vehicle drive control device comprising: an arm provided to be freely bent up and down at a front end portion thereof; and an arm cylinder for bending and extending the arm;
A variable displacement hydraulic pump, a swing drive control valve that is provided corresponding to each of the swing motor, the boom cylinder, and the arm cylinder, and that controls supply / discharge of oil supplied from the hydraulic pump, and boom drive control Hydraulic pressure by connecting a valve and an arm drive control valve, a pump pressure oil passage connecting the hydraulic pump and a swing drive control valve, a boom drive control valve and an arm drive control valve, and the swing drive control valve and the swing motor. A first oil passage for supplying the second oil passage, a second oil passage connecting the boom drive control valve and the rod chamber or bottom chamber of the boom cylinder, and the arm drive control valve and the bottom chamber or rod chamber of the arm cylinder. A first pilot connected to each of a third oil passage to be connected, and the first oil passage, the second oil passage, and the third oil passage. Road, the second pilot oil path, the third pilot oil path, and the first pilot oil path, the second pilot oil path, and the third pilot oil path, and the hydraulic pressure in these pilot oil paths The pressure between the hydraulic pressure of the pump pressure oil passage and the maximum load pressure is adjusted by changing the capacity of the hydraulic pump according to the highest load pressure with the highest hydraulic pressure to adjust the amount of oil supplied from the hydraulic pump. Oil supply amount adjusting means for setting the difference to a predetermined constant value, and each of the first oil passage, the second oil passage, and the third oil passage, the first pilot oil passage, the second pilot oil The highest load pressure having the highest hydraulic pressure among the hydraulic pressures of the road and the third pilot oil passage is received as the pilot pressure, and the oil supplied to the swing motor, the boom cylinder and the arm cylinder exceeds the maximum load pressure. The first pressure compensation valve, the second pressure compensation valve, the third pressure compensation valve, and the pump pressure oil passage that are set to a predetermined pressure are provided in the pump pressure oil passage so that the oil pressure in the pump pressure oil passage does not exceed a predetermined relief pressure. And a relief valve to
The first pilot oil passage is provided in the first pilot oil passage, and communicates the first pilot oil passage with the first pressure compensation valve when an allowable maximum load pressure lower than the relief pressure is received as the maximum load pressure. Equipped with pilot oil passage communication means,
The first pressure compensation valve is supplied from the swing drive control valve to the swing motor when receiving the hydraulic pressure acting on the swing motor through the first pilot oil passage by the pilot oil passage communicating means. A drive control device for a work vehicle, characterized in that the hydraulic pressure of the oil is set to a predetermined hydraulic pressure that exceeds the operating hydraulic pressure.

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