CN108087356B - Front wheel drive control valve of land leveler and hydraulic system - Google Patents

Front wheel drive control valve of land leveler and hydraulic system Download PDF

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Publication number
CN108087356B
CN108087356B CN201711326029.9A CN201711326029A CN108087356B CN 108087356 B CN108087356 B CN 108087356B CN 201711326029 A CN201711326029 A CN 201711326029A CN 108087356 B CN108087356 B CN 108087356B
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front wheel
oil
oil port
control valve
valve
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CN108087356A (en
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刘光喜
李良周
白健信
李大尤
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Guangxi Liugong Machinery Co Ltd
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Guangxi Liugong Machinery Co Ltd
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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
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/165—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for adjusting the pump output or bypass in response to demand
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K17/00—Arrangement or mounting of transmissions in vehicles
    • B60K17/34—Arrangement or mounting of transmissions in vehicles for driving both front and rear wheels, e.g. four wheel drive vehicles
    • B60K17/356—Arrangement or mounting of transmissions in vehicles for driving both front and rear wheels, e.g. four wheel drive vehicles having fluid or electric motor, for driving one or more wheels
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F3/00—Dredgers; Soil-shifting machines
    • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
    • E02F3/76—Graders, bulldozers, or the like with scraper plates or ploughshare-like elements; Levelling scarifying devices
    • E02F3/80—Component parts
    • E02F3/84—Drives or control devices therefor, e.g. hydraulic drive systems
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20546—Type of pump variable capacity
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/255—Flow control functions
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Civil Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Operation Control Of Excavators (AREA)
  • Arrangement And Driving Of Transmission Devices (AREA)

Abstract

The invention relates to front wheel driving of a land leveler, aiming at solving the problem that the linear operation and the steering performance are influenced by the easy unilateral slipping of the front wheel driving of the existing land leveler; the utility model provides a grader front wheel drives hydraulic system, including grader front wheel drive control valve, the variable pump is connected through the P hydraulic fluid port of pipeline with grader front wheel drive control valve, the C1 hydraulic fluid port of grader front wheel drive control valve, the D1 hydraulic fluid port, the C2 hydraulic fluid port, the D2 hydraulic fluid port corresponds and is connected with the right front left wheel hydraulic motor's working oil port, the LS hydraulic fluid port is connected with the load feedback mouth of variable pump, the oil inlet of T hydraulic fluid port and variable pump passes through the pipeline and is connected with hydraulic tank. In the hydraulic system, the left front wheel and the right front wheel are independently controlled, so that the phenomenon of unilateral slipping is avoided, the straight line operation and the steering performance of the land leveler can be ensured, different working condition modes can be selected according to the operation ground conditions, the assisting force action of the front wheels can be flexibly and effectively exerted, and the operation efficiency and the economical efficiency of the whole machine are improved.

Description

Front wheel drive control valve of land leveler and hydraulic system
Technical Field
The present invention relates to motor grader front wheel drive, and more particularly, to a motor grader front wheel drive control valve and a hydraulic system.
Background
The existing front wheel driving system of the land leveler is an open type hydraulic system of a front wheel power-assisted type with a driving pump with two motors, the driving pump absorbs oil from a hydraulic oil tank, outlet pressure oil directly enters two motors connected in parallel after passing through a control valve and then returns to the hydraulic oil tank through the control valve. The flow of the hydraulic oil entering the motor is determined by the valve core opening of the three-position four-way reversing valve in the control valve, and the pressure of the system is determined by the pressure cut-off valve of the driving pump.
When the land leveler starts to run and work, the discharge capacity of the driving pump is at the maximum discharge capacity, the pressure oil output by the driving pump drives the motor to rotate, and the driving pump generates pressure under the action of an external load. When the driving force of the motor is larger than the ground adhesive force, the pressure of the outlet of the driving pump is smaller than the cutting pressure of the pressure cutting valve, the pressure cutting valve does not work, the driving pump is at the maximum discharge capacity, and the motor is at the highest rotating speed. When the driving force of the motor is smaller than the ground adhesive force, the pressure of the outlet of the driving pump reaches the cutting pressure of the pressure cutting valve, the pressure cutting valve acts, the displacement of the driving pump is reduced, and the displacement of the driving pump is increased because the rear wheel continues to push the land leveler to run, the pressure of the outlet of the driving pump is reduced, the pressure cutting valve acts. At this time, the pressure cut-off valve is continuously operated, and the discharge capacity of the driving pump is maintained to make the rotating speed of the front wheel matched with that of the rear wheel.
The pressure oil output by the driving pump is directly connected into the two motors connected in parallel after passing through the control valve, the flow of the pressure oil entering the two motors is freely distributed, when the attachment condition of the driving wheel on one side and the ground is worsened, namely, the ground reaction force received by the driving wheel on the side is reduced, the flow of the pressure oil obtained by the motor on the side can be increased, the rotating speed of the motor on the side is accelerated, the rotating speed of the motor on the other side is reduced or even is not rotated, namely, the unilateral slipping phenomenon of a front wheel, the linear operation working condition of the land leveler cannot be ensured, the steering performance of the land leveler cannot be ensured, and the operation efficiency and the running safety of the land leveler are influenced.
Meanwhile, when the motor is in a stall state, the driving pump is in a state of untimely oil supply, so that the early abrasion of the motor is easily caused, and the service life of the motor is shortened.
Moreover, the pressure of the pressure cut-off valve of the driving pump is set, but the ground conditions can be different due to local potholes, soft soil, dryness and wetness and the like, the load of a working device is continuously changed, the tires of the land leveler are also continuously and temporarily changed, the pressure cut-off valve continuously acts to cause the temporary slip rotation of the front wheels relative to the rear wheels, the assisting force of the front wheels cannot be effectively exerted, the slip rotation at the moment not only causes the abrasion of the tires, but also can cause the deviation or the lateral movement of the whole machine, and the potential safety hazard is serious.
Disclosure of Invention
The invention aims to solve the technical problem that the front wheel driving of the existing land scraper is easy to slip on one side to influence the linear operation and the steering performance, and provides a front wheel driving control valve and a hydraulic system of the land scraper, wherein the front wheel driving can select different working condition modes according to the working ground conditions, can flexibly and effectively exert the assisting force of a front wheel, and improve the working efficiency and the economical efficiency of the whole machine.
The technical scheme for realizing the purpose of the invention is as follows: the front wheel drive control valve of the land leveler is characterized by comprising a C1 oil port and a D1 oil port which are used for being connected with a left front wheel hydraulic motor, a C2 oil port and a D2 oil port which are used for being connected with a right front wheel hydraulic motor, a P oil port for feeding oil, a T oil port for returning oil, an LS oil port for feedback output of a load signal, a left front wheel control valve and a right front wheel control valve which are used for correspondingly controlling the left front wheel hydraulic motor and the right front wheel hydraulic motor, a shuttle valve, a bidirectional oil supplementing valve, an oil returning back pressure valve and a mode selection valve; the left front wheel control valve and the right front wheel control valve are electric proportional reversing valves with the same structure, and are provided with an oil port E, an oil port F, an oil port G, an oil port V and an oil port H, when the left front wheel control valve and the right front wheel control valve are in a middle position, the oil port E is stopped, and the oil port F, the oil port G, the oil port H and the oil port V are mutually communicated; when the oil port E is positioned at the left position, the oil port E is communicated with the oil port G and the oil port V at the same time, and the oil port F is communicated with the oil port H; when the oil port E is positioned at the right position, the oil port E is simultaneously communicated with the oil port H and the oil port V, and the oil port F is communicated with the oil port G; the oil ports G and H of the left front wheel control valve are correspondingly communicated with the oil port C1 and the oil port D1, and the oil ports G and H of the right front wheel control valve are correspondingly communicated with the oil port C2 and the oil port D2; the oil port E of the left front wheel control valve is communicated with the oil port P through a left compensation valve, the left end of the left compensation valve is communicated with the oil port E of the left front wheel control valve, and the right end of the left compensation valve and the oil port V of the left front wheel control valve are simultaneously communicated with one oil inlet of the shuttle valve; an oil port E of the right front wheel control valve is communicated with an oil port P through a right compensation valve, the left end of the right compensation valve is communicated with the oil port E of the right front wheel control valve, the right end of the right compensation valve and an oil port V of the right front wheel control valve are simultaneously communicated with the other oil inlet of the shuttle valve, and an oil outlet of the shuttle valve is communicated with an oil port LS; an oil port F of the left front wheel control valve is connected with an oil inlet of a first bidirectional oil replenishing valve, and two oil outlets of the first bidirectional oil replenishing valve are correspondingly connected with an oil port C1 and an oil port D1; an oil port F of the right front wheel control valve is connected with an oil inlet of a second bidirectional oil replenishing valve, two oil outlets of the second bidirectional oil replenishing valve are correspondingly connected with an oil port C2 and an oil port D2, the oil port F of the left front wheel control valve is communicated with the oil port F of the right front wheel control valve, and the oil return back pressure valve and the mode switching valve are connected in parallel and then connected between the oil ports F and T of the left front wheel control valve and the right front wheel control valve.
Furthermore, the front wheel drive control valve of the land leveler further comprises an overflow valve, and the overflow valve is connected between the oil port P and an oil inlet of the oil return back pressure valve.
Furthermore, in the front wheel drive control valve of the land leveler, damping holes are formed in oil passages of V-shaped oil ports of the left front wheel control valve and the right front wheel control valve.
The technical scheme for realizing the purpose of the invention is as follows: the hydraulic system for driving the front wheel of the land scraper comprises a variable pump, a left front wheel hydraulic motor, a right front wheel hydraulic motor and a hydraulic oil tank and is characterized by further comprising a front wheel driving control valve of the land scraper, wherein an oil outlet of the variable pump is connected with a P oil port of the front wheel driving control valve of the land scraper through a pipeline, a C1 oil port and a D1 oil port of the front wheel driving control valve of the land scraper are correspondingly connected with two working oil ports of the left front wheel hydraulic motor, a C2 oil port and a D2 oil port of the front wheel driving control valve of the land scraper are correspondingly connected with two working oil ports of the right front wheel hydraulic motor, an LS oil port of the front wheel driving control valve of the land scraper is connected with a load feedback port of the variable pump, and a T oil port of the front wheel driving control valve of the land scraper and an oil inlet of the variable pump.
Further, in the front wheel driving hydraulic system of the grader, the front wheel driving hydraulic system further includes a controller and a working mode input device connected to the controller, wherein the electromagnetic control ends of the left and right front wheel control valves and the electromagnetic control end of the mode switching valve are both connected to the output end of the controller, the working mode input device has three working mode outputs of full wheel driving, front wheel crawling driving and front wheel free wheel, when the working mode input device is in three working modes of front wheel crawling driving, front wheel free wheel and full wheel driving, the controller outputs corresponding control signals to enable the left and right front wheel control valves to be in left position, middle position, left position or right position in sequence, when the working mode input device is in the front wheel free wheel working mode, the mode switching valve is in a conducting state, when the working mode input device is in the front wheel crawling driving working mode and the full wheel driving working mode, the mode switching valve is in a cutoff state.
Furthermore, in the front wheel driving hydraulic system of the grader, the front wheel driving hydraulic system further comprises an operating mode selection valve and an operating mode input device connected with the controller and used for selecting operating conditions, an electric control end of the operating mode selection valve is connected with an electric proportional overflow valve connected with the controller, the operating mode selection valve is connected between a hydraulic oil tank and an LS oil port of the front wheel driving control valve of the grader, the operating mode input device has output representing different operating mode, and the controller outputs different currents corresponding to different operating mode modes to enable the operating mode selection valve to work at different pressure levels.
Further, among the above-mentioned land leveler front wheel drive hydraulic system, still include back pressure valve and the outside oil supply of low pressure, the back pressure valve is connected between left front wheel hydraulic motor and the T hydraulic fluid port that right front wheel hydraulic motor is used for the casing oil return and the hydraulic tank, the outside oil supply of low pressure is connected the oil feed end of back pressure valve.
Furthermore, the hydraulic system for driving the front wheels of the land leveler further comprises a rear wheel rotating speed sensor connected with the controller and used for detecting the rotating speed of the rear wheels of the land leveler, and the controller controls the valve core openings of the left front wheel control valve and the right front wheel control valve according to the rotating speed of the rear wheels so as to control the flow output by the driving pump and enable the rotating speed of the front wheels to be consistent with the rotating speed of the rear wheels.
Furthermore, the front wheel driving hydraulic system of the land leveler further comprises a corner sensor for detecting the steering corner of the land leveler, and when the land leveler is in an all-wheel driving or front wheel crawling driving working mode, the controller controls the left front wheel control valve and the right front wheel control valve according to steering angle data detected by the corner sensor so that the left front wheel hydraulic motor and the right front wheel hydraulic motor have corresponding rotating speeds.
Compared with the prior art, the invention has the advantages that the front wheel driving hydraulic system does not cause the front wheel to rotate in a sliding way relative to the rear wheel due to the influence of ground conditions and the load of the working device, and the speed of the front wheel always follows the speed of the rear wheel; meanwhile, the left front wheel and the right front wheel are independently controlled, the unilateral slipping phenomenon caused by different ground adhesive forces of the left front wheel and the right front wheel is avoided, the straight line operation and the steering performance of the land leveler can be guaranteed, moreover, the front wheel driving system can select different working condition modes according to the operation ground conditions, the assisting effect of the front wheels can be flexibly and effectively exerted, and the operation efficiency and the economical efficiency of the whole machine are improved.
Drawings
FIG. 1 is a schematic diagram of the grader front wheel drive hydraulic system of the present invention.
Fig. 2 is a schematic diagram of a grader front wheel drive control valve of the present invention.
Fig. 3 is an electrical control block diagram of the grader front wheel drive hydraulic system of the present invention.
Detailed Description
The following description of the embodiments refers to the accompanying drawings.
As shown in fig. 1 and 3, the hydraulic system for driving the front wheels of the motor grader in the present embodiment includes a hydraulic oil tank 1, a drive pump 2, a working condition mode selection valve 3, a motor grader front wheel drive control valve 4, a left front wheel hydraulic motor 5, a right front wheel hydraulic motor 6, a back pressure valve 7, a controller 8, a rear wheel rotation speed sensor 9, a working mode input device 10, a rotation angle sensor device 11, an engine rotation speed sensor 12, and a working condition mode input device 13.
As shown in fig. 2, the grader front wheel drive control valve 4 includes a left front wheel control valve 401, a first bidirectional makeup valve 402, a shuttle valve 403, a second bidirectional makeup valve 404, a mode switching valve 405, a right makeup valve 406, a right front wheel control valve 407, a return back pressure valve 408, a main relief valve 409, and a left makeup valve 410. The left front wheel control valve 401 and the right front wheel control valve 407 are electric proportional directional solenoid valves having drive solenoids at both ends, the left front wheel control valve 401 has a left front wheel forward solenoid Y1 at the left end and a left front wheel backward solenoid Y2 at the right end, and the right front wheel control valve 407 has a right front wheel forward solenoid Y3 at the left end and a right front wheel backward solenoid Y4 at the right end. The left front wheel control valve 401 is provided with an E1 oil port, an F1 oil port, a G1 oil port, a V1 oil port and an H1 oil port, when the left front wheel control valve is in a middle position, the E1 oil port is closed, and the F1 oil port is communicated with the G1 oil port, the H1 oil port and the V1 oil port; when the oil port is positioned at the left position, the E1 oil port is simultaneously communicated with the G1 oil port and the V1 oil port, and the F1 oil port is communicated with the H1 oil port; when the oil port E1 is positioned at the right position, the oil port E1 is simultaneously communicated with the oil port H1 and the oil port V1, and the oil port F1 is communicated with the oil port G1; the right front wheel control valve 407 has the same structural function as the left front wheel control valve 401, and has an E2 oil port, an F2 oil port, a G2 oil port, a V2 oil port, and an H2 oil port, when the front wheel control valve is in the middle position, the E2 oil port is closed, and the F2 oil port is mutually communicated with the G2 oil port, the H2 oil port, and the V2 oil port; when the oil port is positioned at the left position, the E2 oil port is simultaneously communicated with the G2 oil port and the V2 oil port, and the F2 oil port is communicated with the H2 oil port; when the oil port E2 is positioned at the right position, the oil port E2 is simultaneously communicated with the oil port H2 and the oil port V2, and the oil port F2 is communicated with the oil port G2;
the G1 oil port and the H1 oil port of the left front wheel control valve are correspondingly communicated with the C1 oil port and the D1 oil port, and the G2 oil port and the H2 oil port of the right front wheel control valve are correspondingly communicated with the C2 oil port and the D2 oil port; an oil port E1 of the left front wheel control valve is communicated with an oil port P through the left compensation valve 410, the left end of the left compensation valve 410 is communicated with an oil port E1 of the left front wheel control valve 401, and the right end of the left compensation valve 410 and an oil port V1 of the left front wheel control valve are simultaneously communicated with an oil port S of the shuttle valve; an oil port E2 of the right front wheel control valve is communicated with an oil port P through a right compensation valve 406, the left end of the right compensation valve is communicated with an oil port E2 of the right front wheel control valve, the right end of the right compensation valve and an oil port V2 of the right front wheel control valve are simultaneously communicated with an oil inlet X of the shuttle valve, and an oil outlet Y of the shuttle valve is communicated with an oil port LS; an oil port F1 of the left front wheel control valve is communicated with an oil inlet L1 of the first bidirectional oil replenishing valve 402, and an oil outlet K1 and an oil outlet J1 of the first bidirectional oil replenishing valve 402 are correspondingly communicated with an oil port C1 and an oil port D1; an oil port F2 of the right front wheel control valve is connected with an oil inlet L2 of the second bidirectional oil replenishing valve 404, an oil outlet K2 and an oil outlet J2 of the second bidirectional oil replenishing valve 404 are correspondingly connected with an oil port C2 and an oil port D2, an oil port F1 of the left front wheel control valve is communicated with an oil port F2 of the right front wheel control valve, and the oil return back pressure valve 408 and the mode switching valve 405 are connected in parallel and then connected between the oil ports F and T of the left front wheel control valve and the right front wheel control valve.
The mode switching valve 405 is a two-position two-way electromagnetic valve with an electromagnet at the left end and is provided with a Q oil port and an R oil port, when the mode switching valve 405 is in the right position, the Q oil port and the R oil port are communicated, when the mode switching valve 405 is in the left position, the Q oil port and the R oil port are blocked, the Q oil port of the mode switching valve 405 is communicated with an F1 oil port of the left front wheel control valve 401 and an F2 oil port of the right front wheel control valve 407, and the R oil port of the mode switching valve 405 is communicated with a T0 oil port of the front wheel drive control valve 4 of; the oil return back pressure valve 408 has a U oil port and a W oil port, wherein the U oil port is simultaneously communicated with an F1 oil port of the left front wheel control valve 401, an F2 oil port of the right front wheel control valve 407, an L1 oil port of the first bidirectional oil supply valve 402, and an L2 oil port of the second bidirectional oil supply valve 404, the W oil port of the oil return back pressure valve 408 is communicated with a T oil port of the front wheel drive control valve 4 of the grader, and the T oil port and the T0 oil port of the front wheel drive control valve of the grader are both connected with a hydraulic oil tank.
The driving pump 2 is a load sensing variable pump, the working condition mode selection valve 3 is an electric proportional overflow valve, and the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are radial plunger hydraulic motors.
As shown in fig. 1, the drive pump 2 sucks oil from the hydraulic oil tank 1, an oil outlet P1 is connected with an oil port P of the front wheel drive control valve 4 of the grader, an oil port C1 and an oil port D1 of the front wheel drive control valve 4 of the grader are respectively connected with an oil port a1 and an oil port B1 of the front left wheel hydraulic motor 5, an oil port C2 and an oil port D2 of the front wheel drive control valve 4 of the grader are respectively connected with an oil port a2 of the front right wheel hydraulic motor 6 of the grader, the hydraulic control system comprises a B2 oil port, a T oil port and a T0 oil port of a front wheel drive control valve 4 of the land leveler are connected with an oil tank, an LS oil port of the front wheel drive control valve 4 of the land leveler is connected with a load feedback oil port LS1 of a drive pump 2, an oil inlet of an operating mode selection valve 3 is communicated with a load feedback oil port LS1 of the drive pump 2, an oil outlet is connected with a hydraulic oil tank 1, and an external low-pressure oil source is connected into the T1 oil port of a left front wheel hydraulic motor 5 and the T2 oil port of a right front wheel hydraulic motor through O oil ports and is connected with the hydraulic oil tank 1 through.
As shown in fig. 3, the rear wheel speed sensor 9, the operation mode input device 10, the rotation angle sensor device 11, the engine speed sensor 12, and the operating mode input device 13 are connected to the controller 8, and control ends of the left front wheel forward electromagnet Y1, the left front wheel backward electromagnet Y2, the right front wheel forward electromagnet Y3, the right front wheel backward electromagnet Y4, the mode switching valve electromagnet Y5, and the operating mode selection valve electromagnet Y6 are correspondingly connected to a control output end of the controller 8. The rear wheel rotating speed sensor 9 can directly measure the rotating speed of the rear wheel of the land leveler and can also indirectly measure the rotating speed of the rear wheel by detecting the rotating speed of a certain level of rotating shaft on the gearbox; the operation mode input device 10 may be a toggle switch, for example, the toggle switch has an all-wheel driving mode, a front wheel crawling driving mode and a front wheel free wheel mode, the operation mode input device 10 is in different state toggle positions, and the controller outputs a potential to make the mode switching valve 405 be in the left position or the right position, so as to realize that the front wheel is in the driving state or the free wheel state; the corner sensor device 11 is arranged on a front axle or a front wheel steering knuckle and outputs vehicle steering angle data to the controller 8 in real time; the engine speed sensor 12 detects the speed of the engine and outputs the engine speed data to the controller 8 in real time; the working condition mode input device 13 may be a toggle switch, for example, the toggle switch has a field mode, a sand mode, a snow mode, and the like, and sets a plurality of working condition modes according to the conditions of the working ground, the working condition mode input device 13 is in different mode toggling positions, the controller 8 outputs different current values to the electromagnetic coil of the working condition mode selection valve 3, so that the working condition mode selection valve 3 is in different pressure levels to adjust the output torque of the front wheel hydraulic motor.
In this embodiment, when the grader is not driven by the front wheel, that is, when the working mode input device 10 is in the front wheel free wheel mode, the electromagnet Y5 of the mode switching valve is not powered, the mode switching valve 405 is in the right position, the Q port is turned on with the R port, the electromagnets of the left front wheel control valve 401 and the right front wheel control valve 407 are not powered, the E1 port of the left front wheel control valve 401 is closed, the F1 port is simultaneously turned on with the G1 port, the H1 port and the V1 port, the E2 port of the right front wheel control valve 407 is closed, the F2 port is simultaneously turned on with the G2 port, the H2 port and the V2 port, at this time, the a port a1 and the port B1 of the left front wheel hydraulic motor 5 and the port a2 and the port B2 of the right front wheel hydraulic motor 6 are simultaneously turned on with the oil tank, the external low-pressure oil source is introduced into the housing T hydraulic motor 5 and the housing T hydraulic motor 6, the motor plunger is pressed back to the plunger cavity, so that the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are in a free wheel state.
When the grader is driven only using the front wheels, i.e., when the work mode input device 10 is in the front wheel creep drive mode, the rear axle of the grader has no driving force, and the driving force of the whole grader is provided by the front wheels. At this time, the left front wheel forward electromagnet Y1, the right front wheel forward electromagnet Y3 and the mode switching valve electromagnet Y5 are powered, that is, the left front wheel control valve 401 and the right front wheel control valve 407 are in the left position, the oil port of the left front wheel control valve E1 is communicated with the oil port of G1 and the oil port of V1, the oil port of F1 is communicated with the oil port of H1, the oil port of the right front wheel control valve E2 is communicated with the oil port of G2 and the oil port of V2, the oil port of F2 is communicated with the oil port of H2, the oil port of Q of the mode switching valve is blocked from the oil port of R, at this time, the oil output by the driving pump 2 enters the oil port of a1 of the left front wheel hydraulic motor 5 and the oil port of a2 of the right front wheel hydraulic motor 6 through the front wheel driving control valve 4 of the grader, the oil ports of B1 of the left front wheel hydraulic motor 5 and the B2 of the right wheel hydraulic motor 6 are returned to the oil tank 1 through the T, that is, when the pressure of the V1 port of the left front wheel control valve 401 is greater than the pressure of the V2 port of the right front wheel control valve 407, the pressure of the LS port of the front wheel drive control valve of the grader is the pressure of the V1 port of the left front wheel control valve 401, and vice versa is the pressure of the V2 port of the right front wheel control valve 407; at this time, the speed of the grader is controlled by the engine speed, that is, the controller 8 receives the rotation speed value of the engine rotation speed sensor 12, calculates current values to output corresponding speeds to the forward electromagnet Y1 of the left front wheel control valve 401 and the forward electromagnet Y3 of the right front wheel control valve 407 of the grader front wheel drive control valve, and outputs corresponding flow rates according to the valve opening degrees of the left front wheel control valve 401 and the valve opening degree of the right front wheel control valve 407 to drive the front wheels to move forward by the drive pump 2.
When the grader is driven to advance using all-wheel drive, that is, when the operation mode input device 10 is in the all-wheel drive mode, the left front wheel advance solenoid Y1, the right front wheel advance solenoid Y3, and the mode switching valve solenoid Y5 are energized, that is, the left front wheel control valve 401 and the right front wheel control valve 407 are in the left position, the left front wheel control valve E1 oil port is communicated with the G1 oil port and the V1 oil port, the F1 oil port is communicated with the H1 oil port, the right front wheel control valve E2 oil port is communicated with the G2 oil port and the V2 oil port, the F2 oil port is communicated with the H2 oil port, the Q oil port and the R oil port of the mode switching valve are cut off, at this time, the oil output by the drive pump 2 enters an oil port A1 of the left front wheel hydraulic motor 5 and an oil port A2 of the right front wheel hydraulic motor 6 through the front wheel drive control valve of the grader, and an oil port B1 of the left front wheel hydraulic motor 5 and an oil port B2 of the right front wheel hydraulic motor 6 return to the oil tank 1 through an oil port T of the front wheel drive control valve of the grader; at this time, if the ground adhesion of the left front wheel hydraulic motor 5 is greater than the ground adhesion of the right front wheel hydraulic motor 6, that is, the pressure of the V1 oil port of the left front wheel control valve 401 is greater than the pressure of the V2 oil port of the right front wheel control valve 407, the pressure of the LS oil port of the front wheel drive control valve of the grader is the pressure of the V1 oil port of the left front wheel control valve 401, and conversely, the pressure of the V2 oil port of the right front wheel control valve 407; at this time, the controller 8 receives the rotation speed value of the rear wheel rotation speed sensor 9, calculates the current value of the corresponding speed output to the forward electromagnet Y1 of the left front wheel control valve 401 and the forward electromagnet Y3 of the right front wheel control valve 407 of the grader front wheel drive control valve, and outputs the corresponding flow according to the valve core opening degree of the left front wheel control valve 401 and the valve core opening degree of the right front wheel control valve 407 by the drive pump 2, so that the front wheel speed is consistent with the rear wheel speed; when the speed of the grader changes, that is, the rear wheel rotation speed value acquired by the rear wheel rotation speed sensor 9 changes, the controller 8 recalculates the rear wheel speed, outputs a current value matched with the corresponding speed to the forward electromagnet Y1 of the left front wheel control valve 401 and the forward electromagnet Y3 of the right front wheel control valve 407 of the grader front wheel drive control valve, adjusts the valve core openings of the left front wheel control valve 401 and the right front wheel control valve 407, enables the drive pump 2 to output a flow with the corresponding speed to the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6, and enables the speeds of the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 to be always consistent with the rear wheel speed. Similarly, when the grader is driven in all-wheel drive reverse, i.e., when the operation mode input device 10 is in the all-wheel drive mode, the left front wheel reverse electromagnet Y2, the right front wheel reverse electromagnet Y4, and the mode switching valve electromagnet Y5 are energized, that is, the left front wheel control valve 401 and the right front wheel control valve 407 are in the right position, the oil port of the left front wheel control valve E1 is communicated with the oil port H1 and the oil port V1, the oil port F1 is communicated with the oil port G1, the oil port of the right front wheel control valve E2 is communicated with the oil port H2 and the oil port V2, the oil port F2 is communicated with the oil port G2, the oil port Q and the oil port R of the mode switching valve are cut off, at this time, the oil output by the drive pump 2 enters a B1 oil port of the left front wheel hydraulic motor 5 and a B2 oil port of the right front wheel hydraulic motor 6 through the front wheel drive control valve of the grader, and an A1 oil port of the left front wheel hydraulic motor 5 and an A2 oil port of the right front wheel hydraulic motor 6 return to the oil tank 1 through a T oil port of the front wheel drive control valve of the grader; at this time, if the ground adhesion of the left front wheel hydraulic motor 5 is greater than the ground adhesion of the right front wheel hydraulic motor 6, that is, the pressure of the V1 oil port of the left front wheel control valve 401 is greater than the pressure of the V2 oil port of the right front wheel control valve 407, the pressure of the LS oil port of the front wheel drive control valve of the grader is the pressure of the V1 oil port of the left front wheel control valve 401, and conversely, the pressure of the V2 oil port of the right front wheel control valve 407; at this time, the controller 8 receives the rotation speed value of the rear wheel rotation speed sensor 9, calculates the current value of the corresponding speed output to the back electromagnet Y2 of the left front wheel control valve 401 and the back electromagnet Y4 of the right front wheel control valve 407 of the grader front wheel drive control valve, and outputs the corresponding flow according to the valve core opening degree of the left front wheel control valve 401 and the valve core opening degree of the right front wheel control valve 407 by the drive pump 2, so that the front wheel speed is consistent with the rear wheel speed; when the speed of the grader changes, that is, the rear wheel rotation speed value acquired by the rear wheel rotation speed sensor 9 changes, the controller 8 recalculates the rear wheel speed, outputs a current value matching the corresponding speed to the backward electromagnet Y2 of the left front wheel control valve 401 and the backward electromagnet Y4 of the right front wheel control valve 407 of the grader front wheel drive control valve, adjusts the valve core openings of the left front wheel control valve 401 and the right front wheel control valve 407, enables the drive pump 2 to output a flow of the corresponding speed to the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6, and enables the speeds of the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 to be always consistent with the rear wheel speed.
When the grader steers with the front wheel power assist, that is, when the grader steers in the all-wheel drive mode or the creeping mode, the steering angle sensor 11 detects the steering angle, and the controller 8 receives the steering angle data output by the steering angle sensor 11, calculates and adjusts the current values output to the electromagnets of the left front wheel control valve 401 and the right front wheel control valve 407 of the grader front wheel drive control valve to adjust the valve core openings of the left front wheel control valve 401 and the right front wheel control valve 407, and adjusts the requirements of different speeds of the inner wheel and the outer wheel during the steering of the grader; when the land leveler runs straight, the controller 8 outputs the same current value to the electromagnet of the left front wheel control valve 401 and the electromagnet of the right front wheel control valve 407 of the control valve 4, so that the valve core openings of the left front wheel control valve 401 and the right front wheel control valve 407 are equal, the rotating speeds of the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are made to be the same, and the land leveler is guaranteed to run straight; when the grader turns left, the controller 8 decreases the current value output to the electromagnet of the left front wheel control valve 401 of the grader front wheel drive control valve, and increases the current value output to the electromagnet of the right front wheel control valve 407 of the grader front wheel drive control valve at the same time, so that the spool opening increment of the left front wheel control valve 401 is negative, that is, the spool opening decreases, so that the speed of the left front wheel hydraulic motor 5 decreases, and the spool opening increment of the right front wheel control valve 407 is positive, that is, the spool opening increases, so that the speed of the right front wheel hydraulic motor 6 increases; similarly, when the grader turns right, the controller 8 increases the current value output to the electromagnet of the left front wheel control valve 401 of the grader front wheel drive control valve, and simultaneously decreases the current value output to the electromagnet of the right front wheel control valve 407 of the grader front wheel drive control valve, so that the spool opening increment of the left front wheel control valve 401 is positive, that is, the spool opening is increased, so that the left front wheel speed hydraulic motor is increased by 5 degrees, and the spool opening increment of the right front wheel control valve 407 is negative, that is, the spool opening is decreased, so that the speed of the right front wheel hydraulic motor 6 is decreased; and the increment of the valve core opening of the electric proportional reversing valve is increased along with the increase of the steering angle, so that the smooth steering of the land scraper is ensured when the land scraper drives to steer by using a front wheel, and the maximum function of the front wheel assisting force is exerted.
In this embodiment, a plurality of operating modes may be set according to the conditions of the ground on which the motor grader works, and the output torques of the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are adjusted. When the ground adhesion is large, the on-site mode is selected by the toggle switch of the working condition mode input device 13, the controller 8 outputs a small current value or no current to the electromagnetic coil of the working condition mode selection valve 3, so that the working condition mode selection valve 3 is in a large pressure grade, at the moment, the torque output by the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 is maximum, and the front wheel hydraulic motors exert all the power-assisting capacity; when the ground adhesion is general, the shifting switch of the working condition mode input device 13 selects a sand ground mode, the controller 8 outputs a medium current value to the electromagnetic coil of the working condition mode selection valve 3 to enable the working condition mode selection valve 3 to be in a medium pressure grade, and at the moment, the torques output by the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are medium, so that the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 can exert the power assisting capacity without slipping the front wheels; when the ground adhesion is small, the shifting switch of the working condition mode input device 13 selects the snow mode, the controller 8 outputs a large current value to the electromagnetic coil of the working condition mode selection valve 3, so that the working condition mode selection valve 3 is in a low-pressure grade, and at the moment, the torque output by the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 is small, so that the front wheel hydraulic motor can exert the power-assisted capacity without slipping the front wheels. When the land leveler works, different working condition modes are flexibly selected according to the ground working condition, the function of the front wheel assisting force can be effectively exerted, and the working efficiency and the fuel economy of the whole machine can be improved.
In this embodiment, when the grader is in the overspeed state in which the oil supply of the left front wheel hydraulic motor 5 is not sufficient when the front wheel assist is used, that is, the actual speed of the grader exceeds the rotation speed of the left front wheel hydraulic motor 5, at this time, the first bidirectional oil supply valve 402 is opened in time to supply the oil in the oil return chamber of the left front wheel hydraulic motor 5 to the oil inlet chamber of the left front wheel hydraulic motor 5. That is, when the left front wheel hydraulic motor 5 is over-running, the L1 port of the first bidirectional oil recharging valve 402 is communicated with the K1 port, so that the oil in the B1 port of the left front wheel hydraulic motor 5 is replenished to the a1 port of the left front wheel hydraulic motor 5 through the F1 port of the left front wheel control valve 401, the L1 port of the first bidirectional oil recharging valve 402 and the K1 port; similarly, when the right front wheel hydraulic motor 6 advances and overruns, the L2 port of the second bidirectional oil recharging valve 404 is communicated with the K2 port, so that the oil in the B2 port of the right front wheel hydraulic motor 6 passes through the F2 port of the right front wheel control valve 407, the L2 port of the second bidirectional oil recharging valve 404 and the K2 port to replenish the oil in the a2 port of the right front wheel hydraulic motor 6; similarly, when the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 move backward and overspeed, the L1 oil port of the first bidirectional oil replenishing valve 402 is communicated with the J1 oil port, so that the oil in the a1 oil port of the left front wheel hydraulic motor 5 passes through the F1 oil port of the left front wheel control valve 401, the L1 oil port of the first bidirectional oil replenishing valve 402 and the J1 oil port to replenish the oil in the B1 oil port of the left front wheel hydraulic motor 5; the L2 port of the second bidirectional oil charging valve 404 is communicated with the J2 port, and the oil in the a2 port of the right front wheel hydraulic motor 6 passes through the F2 port of the right front wheel control valve 407, the L2 port of the second bidirectional oil charging valve 404 and the J2 port to be charged to the B2 port of the right front wheel hydraulic motor 6; the left front wheel hydraulic motor 5 and the right front wheel hydraulic motor 6 are effectively protected, and the service life of the left front wheel hydraulic motor 5 and the service life of the right front wheel hydraulic motor 6 are prolonged.
The invention has the advantages that the problem that the front wheel drives the hydraulic system to lead the front wheel to rotate in a sliding way relative to the rear wheel due to the influence of ground conditions and the load of a working device is solved, and the speed of the front wheel always follows the speed of the rear wheel; meanwhile, the left front wheel and the right front wheel are independently controlled, the unilateral slipping phenomenon caused by different ground adhesive forces of the left front wheel and the right front wheel is avoided, the straight line operation and the steering performance of the land leveler can be guaranteed, moreover, the front wheel driving system can select different working condition modes according to the operation ground conditions, the assisting effect of the front wheels can be flexibly and effectively exerted, and the operation efficiency and the economical efficiency of the whole machine are improved.

Claims (9)

1. A front wheel drive control valve of a land leveler is characterized by comprising a C1 oil port and a D1 oil port which are used for being connected with a left front wheel hydraulic motor, a C2 oil port and a D2 oil port which are used for being connected with a right front wheel hydraulic motor, a P oil port for feeding oil, a T oil port for returning oil, an LS oil port for feedback output of a load signal, a left front wheel control valve and a right front wheel control valve which are used for correspondingly controlling the left front wheel hydraulic motor and the right front wheel hydraulic motor, a shuttle valve, a bidirectional oil supplementing valve, an oil returning back pressure valve and a mode selection valve; the left front wheel control valve and the right front wheel control valve are electric proportional reversing valves with the same structure, and are provided with an oil port E, an oil port F, an oil port G, an oil port V and an oil port H, when the left front wheel control valve and the right front wheel control valve are in a middle position, the oil port E is stopped, and the oil port F, the oil port G, the oil port H and the oil port V are mutually communicated; when the oil port E is positioned at the left position, the oil port E is communicated with the oil port G and the oil port V at the same time, and the oil port F is communicated with the oil port H; when the oil port E is positioned at the right position, the oil port E is simultaneously communicated with the oil port H and the oil port V, and the oil port F is communicated with the oil port G; the oil ports G and H of the left front wheel control valve are correspondingly communicated with the oil port C1 and the oil port D1, and the oil ports G and H of the right front wheel control valve are correspondingly communicated with the oil port C2 and the oil port D2; the oil port E of the left front wheel control valve is communicated with the oil port P through a left compensation valve, the left end of the left compensation valve is communicated with the oil port E of the left front wheel control valve, and the right end of the left compensation valve and the oil port V of the left front wheel control valve are simultaneously communicated with one oil inlet of the shuttle valve; an oil port E of the right front wheel control valve is communicated with an oil port P through a right compensation valve, the left end of the right compensation valve is communicated with the oil port E of the right front wheel control valve, the right end of the right compensation valve and an oil port V of the right front wheel control valve are simultaneously communicated with the other oil inlet of the shuttle valve, and an oil outlet of the shuttle valve is communicated with an oil port LS; an oil port F of the left front wheel control valve is connected with an oil inlet of a first bidirectional oil replenishing valve, and two oil outlets of the first bidirectional oil replenishing valve are correspondingly connected with an oil port C1 and an oil port D1; an oil port F of the right front wheel control valve is connected with an oil inlet of a second bidirectional oil replenishing valve, two oil outlets of the second bidirectional oil replenishing valve are correspondingly connected with an oil port C2 and an oil port D2, the oil port F of the left front wheel control valve is communicated with the oil port F of the right front wheel control valve, and the oil return back pressure valve and the mode switching valve are connected in parallel and then connected between the oil ports F and T of the left front wheel control valve and the right front wheel control valve.
2. The grader front wheel drive control valve according to claim 1, further comprising an overflow valve connected between the oil port P and the oil inlet of the return back pressure valve.
3. The grader front wheel drive control valve according to claim 1 or 2, wherein the damping holes are provided in the oil passages of the V oil ports of the left front wheel control valve and the right front wheel control valve.
4. A front wheel driving hydraulic system of a grader comprises a variable pump, a left front wheel hydraulic motor, a right front wheel hydraulic motor and a hydraulic oil tank and is characterized by further comprising the front wheel driving control valve of the grader as claimed in any one of claims 1 to 3, wherein an oil outlet of the variable pump is connected with a P oil port of the front wheel driving control valve of the grader through a pipeline, a C1 oil port and a D1 oil port of the front wheel driving control valve of the grader are correspondingly connected with two working oil ports of the left front wheel hydraulic motor, a C2 oil port and a D2 oil port of the front wheel driving control valve of the grader are correspondingly connected with two working oil ports of the right front wheel hydraulic motor, an LS oil port of the front wheel driving control valve of the grader is connected with a load feedback port of the variable pump, and a T oil port of the front wheel driving control valve of the grader and an oil inlet of the variable pump are connected with the hydraulic oil tank.
5. The front wheel drive hydraulic system of a grader as in claim 4 further comprising a controller, and a work mode input device connected to the controller, wherein the electromagnetic control ends of the left and right front wheel control valves and the electromagnetic control end of the mode switching valve are connected to the output end of the controller, the work mode input device has three work mode outputs of all-wheel drive, front wheel crawling drive, and front wheel free wheel, the work mode input device outputs corresponding control signals to make the left and right front wheel control valves be in left, middle, left, or right positions in turn when the work mode input device is in the front wheel free wheel work mode, and when the working mode input device is in a front wheel crawling driving working mode and an all-wheel driving working mode, the mode switching valve is in a cut-off state.
6. The grader front wheel drive hydraulic system according to claim 5, further comprising a working condition mode selection valve and a working condition input device connected with the controller and used for selecting working conditions, wherein an electric control end of the working condition mode selection valve is connected with the electric proportional overflow valve connected with the controller, the working condition mode selection valve is connected between the hydraulic oil tank and the LS oil port of the grader front wheel drive control valve, the working condition input device has outputs representing different working condition modes, and the controller outputs different currents corresponding to different working condition modes to enable the working condition mode selection valve to work at different pressure levels.
7. The grader front wheel drive hydraulic system according to claim 4, further comprising a back pressure valve connected between the T ports of the left and right front wheel hydraulic motors for casing oil return and a hydraulic oil tank, and a low pressure external oil source connected at an oil inlet end of the back pressure valve.
8. The grader front wheel drive hydraulic system according to claim 5, further comprising a rear wheel speed sensor connected to the controller for detecting the rotational speed of the rear wheels of the grader, wherein the controller controls the spool openings of the left and right front wheel control valves according to the rotational speed of the rear wheels so as to control the output flow of the drive pump to make the rotational speed of the front wheels consistent with the rotational speed of the rear wheels.
9. The grader front wheel drive hydraulic system according to claim 5, further comprising a steering angle sensor for detecting a steering angle of the grader, wherein the controller controls the left front wheel control valve and the right front wheel control valve to allow the left front wheel hydraulic motor and the right front wheel hydraulic motor to have corresponding rotation speeds according to steering angle data detected by the steering angle sensor when the grader front wheel drive or front wheel creep drive operating mode is performed.
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CN108944432A (en) * 2018-06-29 2018-12-07 山推工程机械股份有限公司 A kind of travelling system of spreader and paver
CN109356894A (en) * 2018-10-22 2019-02-19 广西柳工机械股份有限公司 Land leveller front-wheel drive control valve and hydraulic system
CN109404353A (en) * 2018-12-17 2019-03-01 广西柳工机械股份有限公司 Land leveller front-wheel drive control valve and hydraulic system
CN109404354A (en) * 2018-12-17 2019-03-01 广西柳工机械股份有限公司 Land leveller front-wheel drive control valve and hydraulic system
CN109973453A (en) * 2019-04-01 2019-07-05 广西柳工机械股份有限公司 Knife plate automatically controls valve group, hydraulic system and Work machine

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