Electric control positive flow hydraulic system and bulldozer

Abstract

The invention discloses an electric control positive flow hydraulic system and a bulldozer. A first working port of a multi-way valve in the system is connected with a large cavity of a lifting oil cylinder, a second working port is connected with a small cavity of the lifting oil cylinder, a third working port is connected with a right inclined oil cylinder and a small cavity of a left inclined oil cylinder through inclined valves, and a fourth working port is connected with a large cavity of the left inclined oil cylinder; when the push shovel does not act, the pump I and the pump II output at standby flow; when the push shovel ascends and descends, the first pump and the second pump converge through the multi-way valve to provide flow; the multi-way valve is matched with the inclined valve, and when the push shovel inclines leftwards and rightwards, synchronous action of the left inclined oil cylinder and the right inclined oil cylinder is achieved. When the push shovel bends forwards or backwards, synchronous proportional action of the left inclined oil cylinder and the right inclined oil cylinder is realized; when the push shovel ascends, descends and inclines at the same time, the first pump provides ascending and descending flow, the second pump provides inclining flow, and composite action is achieved. According to the invention, the energy loss can be reduced, and the lifting and tilting composite action under the load condition is realized; and meanwhile, when the push shovel inclines leftwards and rightwards and tilts, the left and right inclined oil cylinders synchronously stretch out and draw back.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic control, and in particular relates to an electronically controlled positive flow hydraulic system and a bulldozer. Background Art

[0002] In the prior art, the working hydraulic system of the bulldozer is a fixed displacement pump matched with an open center multi-way valve hydraulic system, or a variable displacement piston pump matched with a closed center load-sensitive multi-way valve hydraulic system. The fixed displacement pump hydraulic system also maintains a large flow output when the bulldozer does not need to move, and most of the output flow returns to the oil tank after passing through the main valve. In the process, there is a large flow friction and energy loss caused by throttling. In addition, it is difficult for these systems to achieve the combined action of lifting and tilting of the bulldozer under load. At the same time, when the bulldozer tilts left and right and pitches, the left and right tilt cylinders are not synchronized, making it difficult for the bulldozer to reach the expected state. Summary of the invention

[0003] In order to solve the deficiencies in the prior art, the present invention provides an electronically controlled positive flow hydraulic system and a bulldozer. When the bulldozer is not in motion, the electronically controlled working pump does not output flow or outputs at a smaller standby flow, thereby reducing energy loss. At the same time, the lifting and tilting compound actions under load are realized. At the same time, when the bulldozer is tilted left and right and pitched, the left and right tilt cylinders are synchronously extended and retracted.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: In a first aspect, an electrically controlled positive flow hydraulic system is provided, comprising: outlets of pump 1 and pump 2 are respectively connected to inlet P1 and inlet P2 of a multi-way valve, working port 1 of the multi-way valve is connected to a large chamber of a lifting cylinder, working port 2 is connected to a small chamber of the lifting cylinder, working port 3 is connected to the small chambers of a right tilt cylinder and a left tilt cylinder through a tilt valve, and working port 4 is connected to a large chamber of a left tilt cylinder; when the dozer is not in motion, pump 1 and pump 2 do not output flow or output at a standby flow; when the dozer is lifted and lowered, pump 1 and pump 2 provide an action flow through the confluence of the multi-way valve; the multi-way valve cooperates with the tilt valve to achieve synchronous action of the left and right tilt cylinders when the dozer is tilted left or right; when the dozer is tilted forward or backward, synchronous proportional action of the left and right tilt cylinders is achieved; when the dozer is lifted and tilted simultaneously, pump 1 provides a lifting action flow, and pump 2 provides a tilting action flow, to achieve a compound action.

[0005] Further, the multi-way valve includes: oil port 1 of valve core 1 and valve core 2 is respectively connected to the inlet P1 and inlet P2 of the multi-way valve, oil port 2 of valve core 1 and valve core 2 is both connected to the inlet of valve core 3, and the outlet of valve core 3 is connected to the oil return port of the multi-way valve; oil port 4 of valve core 1 is connected to the inlet of the load holding valve, the outlet of valve 1, and the inlet of valve 2, the outlet of the load holding valve is connected to the working port 1 of the multi-way valve, and the inlet of valve 1 and the outlet of valve 2 are connected to the oil return port of the multi-way valve; oil port 6 of valve core 1 is connected to the working port 2 of the multi-way valve; oil port 4 of valve core 2 is connected to the working port 3 of the multi-way valve, and oil port 6 is connected to the working port 4 of the multi-way valve.

[0006] Furthermore, the multi-way valve further comprises: a valve three connected between the inlet P1 of the multi-way valve and the oil return port, and a valve four connected between the inlet P2 of the multi-way valve and the oil return port.

[0007] Furthermore, the multi-way valve also includes: valve five and valve six for controlling the switching of valve core one, valve seven and valve eight for controlling the switching of valve core two, and valve nine for controlling the switching of valve core three; the inlets of valves five to nine are all connected to the pilot port of the multi-way valve.

[0008] Furthermore, the tilt valve includes a valve core four and valves twelve and thirteen for controlling the switching of the valve core four.

[0009] Furthermore, it also includes pump three, the outlet of pump three is connected to the inlet of the pilot oil source valve and the inlet of the relief valve, the outlet of the pilot oil source valve is connected to the pilot ports of the multi-way valve and the tilt valve respectively; the outlet of the relief valve is connected to the oil tank; the outlet of the pilot oil source valve is connected to the pilot port of the load holding valve through valve ten.

[0010] Furthermore, the oil return port of the multi-way valve is connected to the oil tank through an oil return back pressure valve and an oil return filter.

[0011] Furthermore, when the bulldozer is not in motion, pump one and pump two output at a standby flow rate, the multi-way valve is in the middle position, and the pressure oil output by pump one is discharged from the oil return port of the multi-way valve through the inlet P1 of the multi-way valve, valve core one, and valve core three; the pressure oil output by pump two is discharged from the oil return port of the multi-way valve through the inlet P2 of the multi-way valve, valve core two, and valve core three; the pilot oil output by pump three is discharged into the oil tank through the overflow valve.

[0012] Furthermore, when the bulldozer is lifted, valve six is ​​energized proportionally, and valve core one is switched to the lifting position; valve nine is energized, and valve core three is switched to the cut-off position; the solenoid valve in the load holding valve is energized, and the pilot oil pushes open the valve core of the load holding valve. Pump one and pump two are energized proportionally to increase the displacement, and the output pressure oil of pump one enters through the inlet P1 of the multi-way valve, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and passes through the middle position of valve core two and the lifting position of valve core one, and then merges with the oil from inlet P1, and after merging, enters the lifting position of valve core one through valve eleven, and then flows into the small chamber of the lifting cylinder through the working port two of the multi-way valve. At this time, the bulldozer is lifted.

[0013] Furthermore, when the bulldozer is lowered, valve five is energized proportionally, and valve core one is switched to the lowered position; the pressure oil in the small chamber of the lifting cylinder flows out under the action of the deadweight of the bulldozer push arm and the tilt cylinder, and is discharged through the working port two of the multi-way valve and the lowered position of valve core one; valve nine is energized, and valve core three is switched to the cut-off position; the solenoid valve in the load holding valve is energized, and the pilot oil pushes open the valve core of the load holding valve, and pump one and pump two are energized proportionally to increase the displacement, and the output pressure oil of pump one enters through the inlet P1 of the multi-way valve, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and passes through the middle position of valve core two and the lowered position of valve core one, and then merges with the oil from inlet P1, and after merging, enters the lowered position of valve core one through valve eleven, and then flows into the large chamber of the lifting cylinder through the working port one of the multi-way valve, and the bulldozer is lowered.

[0014] Furthermore, when the bulldozer is lifted / lowered to a set limit position, the buffer valve provided on the lifting cylinder piston opens to balance the pressure on both sides of the piston and play a buffering role.

[0015] Furthermore, when the bulldozer floats and descends, valve five obtains floating current, and valve core one switches to a floating position; the large and small chambers of the lifting cylinder are connected, and the bulldozer descends.

[0016] Furthermore, when the bulldozer tilts forward, valve seven is proportionally energized, valve core two is switched to the lower position, the tilt valve is energized, the main valve core of the tilt valve is switched to the right position, pump two is proportionally energized to increase the displacement, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and enters the large chamber of the left tilt cylinder through the lower position of valve core two and the working port four of the multi-way valve. The pressure oil in the small chamber of the left tilt cylinder enters the large chamber of the right tilt cylinder through the right position of the tilt valve, and the left tilt cylinder and the right tilt cylinder extend at the same time, and the bulldozer tilts forward.

[0017] Furthermore, when the bulldozer is tilted backward, valve eight is proportionally energized, valve core two is switched to the upper position, the tilt valve is energized, the main valve core of the tilt valve is switched to the right position, pump two is proportionally energized to increase the displacement, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and enters the small chamber of the right tilt cylinder through the upper position of valve core two, the working port three of the multi-way valve, and the right position of the tilt valve. The pressure oil in the large chamber of the right tilt cylinder enters the small chamber of the left tilt cylinder through the right position of the tilt valve, and the left tilt cylinder and the right tilt cylinder retract at the same time, and the bulldozer tilts backward.

[0018] Furthermore, when the dozer blade tilts forward / backward to a set limit position, the buffer valve provided on the tilt cylinder piston opens to balance the pressure on both sides of the piston and play a buffering role.

[0019] Furthermore, when the bulldozer tilts to the left, valve eight is proportionally energized, valve core two is switched to the upper position, pump two is proportionally energized to increase the displacement, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and enters the large chamber of the right tilt cylinder through the upper position of valve core two, the working port three of the multi-way valve, and the middle position of the tilt valve. The pressure oil in the small chamber of the right tilt cylinder enters the small chamber of the left tilt cylinder through the middle position of the tilt valve, the left tilt cylinder retracts, and the bulldozer tilts to the left.

[0020] Furthermore, when the bulldozer tilts to the right, valve seven is proportionally energized, valve core two is switched to the lower position, pump two is proportionally energized to increase the displacement, and the pressure oil output by pump two enters through the inlet P2 of the multi-way valve, and enters the large chamber of the left tilt cylinder through the lower position of valve core two and the working port four of the multi-way valve. The pressure oil in the small chamber of the left tilt cylinder enters the small chamber of the right tilt cylinder through the middle position of the tilt valve, the right tilt cylinder retracts, and the bulldozer tilts to the right.

[0021] Furthermore, when the bulldozer tilts to the left and the tilt valve switches to the left position, valve eight is proportionally energized, valve core two switches to the upper position, pump two is proportionally energized to increase the displacement, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and enters the small chamber of the left tilt cylinder through the upper position of valve core two, the working port three of the multi-way valve, and the left position of the tilt valve, and the left tilt cylinder retracts.

[0022] When the bulldozer tilts to the right and the tilt valve switches to the left position, valve seven is proportionally energized, valve core two switches to the lower position, pump two is proportionally energized to increase the displacement, and the output pressure oil of pump two enters through the inlet P2 of the multi-way valve, and enters the large chamber of the left tilt cylinder through the lower position of valve core two and the working port four of the multi-way valve, and the left tilt cylinder extends.

[0023] In a second aspect, a bulldozer is provided, wherein the bulldozer is equipped with an electronically controlled positive flow hydraulic system as described in the first aspect.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the conventional bulldozer working hydraulic system, the present invention can realize the compound action between the bulldozer lifting action and the tilting action, which can make the bulldozer quickly reach the driver's expected state, meet the needs of various complex working conditions, and improve the operating efficiency of the whole machine; (2) Compared with the conventional bulldozer working hydraulic system, the present invention can achieve synchronous left and right tilting of the bulldozer, synchronous forward and backward tilting movements, and single-cylinder tilting movements, thereby improving working efficiency; (3) Compared with the conventional bulldozer working hydraulic system, the present invention can realize the on-demand supply of hydraulic system flow. When the working device does not need to move, the electronically controlled working pump does not output or outputs at a relatively small flow rate, thereby minimizing the power and energy loss of the whole machine caused by flow circulation or throttling of the hydraulic system when the working device does not need to move, thereby improving the fuel economy or power utilization rate of the whole machine (pure electric model) and reducing the cost of use; (4) The main working pump and main working valve and other components of the present invention are all electronically controlled, and the control process is controlled by electrical signals. Compared with mechanical and pilot hydraulic control systems, the operator's operating intensity is reduced, thereby reducing the operator's fatigue caused by long-term operation, improving the operating comfort of the entire machine, and providing a realistic foundation for the subsequent development of pure electrification and unmanned operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the principle of an electronically controlled positive flow hydraulic system provided by an embodiment of the present invention; Figure 2 yes Figure 1 Schematic diagram of the principle of the multi-way valve; Figure 3 yes Figure 1 Schematic diagram of the principle of the middle tilt valve; In the figure: 1, oil tank; 2, pump 1; 3, pump 2; 4, pump 3; 5, multi-way valve; 6, return oil back pressure valve; 7, load holding valve; 8, valve 10; 9, tilt valve; 10, left lifting cylinder; 11, right lifting cylinder; 12, left tilt cylinder; 13, right tilt cylinder; 14, pilot oil source valve; 15, overflow valve; 16, return oil filter; 17, buffer valve; 501, valve core one; 502, valve core two; 503, valve core three; 504, valve one; 505, valve two; 506, valve three; 507, valve four; 508, valve five; 509, valve six; 510, valve seven; 511, valve eight; 512, valve nine; 513, valve eleven; 91. Valve core four; 92. Valve twelve; 93. Valve thirteen. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0027] Embodiment 1 like Figure 1~Figure 3As shown, an electronically controlled positive flow hydraulic system for a bulldozer includes an oil tank 1, a pump 1 2, a pump 2 3, a pump 3 4, a multi-way valve 5, an oil return back pressure valve 6, a load holding valve 7, a valve 10 8, a tilt valve 9, a left lift cylinder 10, a right lift cylinder 11, a left tilt cylinder 12, a right tilt cylinder 13, a pilot oil source valve 14, a relief valve 15, an oil return filter 16, a buffer valve 17, a valve core 1 501, a valve core 2 502, a valve core 3 503, a valve 1 504, a valve 2 505, a valve 3 506, a valve 4 507, a valve 508, a valve 6 509, a valve 7 510, a valve 8 511, a valve 9 512, a valve 11 513, a valve core 4 91, a valve 12 92, and a valve 13 93 ; Among them, pump one 2 and pump two 3 are electrically controlled plunger pumps; pump three 4 is a pilot gear pump; multi-way valve 5 is an electrically controlled open center multi-way valve; valve ten 8 is a two-position three-way solenoid valve; tilt valve 9 is an electrically controlled tilt valve; valve one 504 and valve eleven 513 are one-way valves; valve two 505 is an overflow valve; valve three 506 and valve four 507 are safety valves; valve five 508, valve six 509, valve seven 510, valve eight 511, valve twelve 92, and valve thirteen 93 are electric proportional pressure reducing valves; valve nine 512 is a cut-off electric proportional valve; valve core one 501 is a lifting (lowering) valve core; valve core two 502 is a tilting valve core; valve core three 503 is a cut-off valve core; valve core four 91 is the main valve core of the electrically controlled tilt valve.

[0028] The multi-way valve 5 includes an oil inlet, a lifting, a tilting, a cut-off and an oil return. The lifting is a four-position six-way valve, and its valve core includes a middle position, a lifting position, a lowering position and a floating position. A main safety valve is provided in front of the oil inlet of the lifting and tilting connections. The lifting is connected to the large-cavity oil port of the lifting cylinder, and an overload protection valve and an oil replenishing valve are provided inside. The lifting is connected to the large-cavity oil port of the lifting cylinder, and a load holding valve is provided outside. The tilting is a three-position six-way valve, and its valve core includes a middle position and two cross-switching positions. The cut-off is a two-position two-way valve, and its valve core has only two positions, namely, on and off. There are four pilot electric proportional valves at both ends of the lifting and tilting, and a pilot electric proportional valve or solenoid valve is provided at one end of the cut-off. The electric-controlled tilting valve is a three-position four-way valve, including two cross-switching positions and a cylinder lock position. Both ends of the valve stem are electric proportional control valves, and the proportional control pilot oil controls the movement and reversal of the main valve stem. A number of buffer valves are provided on the large piston inside the lifting cylinder, which play a buffering role when the cylinder piston moves to the extreme positions at both ends. There are several buffer valves on the large piston inside the left and right tilt cylinders, which play the role of stopping, buffering and overflowing when the cylinder pistons move to the extreme positions at both ends.

[0029] The bulldozer movement requires the manipulation of the electric control handle, which has four movement directions: front, back, left, and right. The handle can be pushed to the front and rear ends to pass the hard point. There is a hard point position, which can control the bulldozer to achieve floating movement. A proportional adjustment roller in the forward and backward rolling direction is integrated on the top of the electric control handle. The thumb can be used to roll forward and backward to control the bulldozer's forward tilt movement when rolling forward, and to control the bulldozer's backward tilt movement when rolling backward. A button is integrated on the back of the electric control handle. When the button is not pressed, it is set to the double-cylinder action mode of the left and right tilt cylinders. When the button is pressed, it is the single-cylinder movement mode that locks one side of the tilt cylinder and only moves the other side of the cylinder. The opposite action mode of the button can also be set through the screen.

[0030] The outlets of pump 1 2 and pump 2 3 are connected to the inlet P1 and the inlet P2 of the multi-way valve 5 respectively; the working port 1 of the multi-way valve 5 is connected to the large chamber of the lifting cylinder, the working port 2 is connected to the small chamber of the lifting cylinder, the working port 3 is connected to the small chambers of the right tilt cylinder 13 and the left tilt cylinder 12 through the tilt valve 9, and the working port 4 is connected to the large chamber of the left tilt cylinder 12; when the bulldozer is not in motion, pump 1 2 and pump 2 3 do not output flow or output at a standby flow; when the bulldozer is lifted and lowered, pump 1 2 and pump 2 3 merge through the multi-way valve 5 to provide an action flow; the multi-way valve 5 cooperates with the tilt valve 9 to realize the synchronous action of the left and right tilt cylinders when the bulldozer is tilted left or right; when the bulldozer is tilted forward or backward, the synchronous proportional action of the left and right tilt cylinders is realized; when the bulldozer is lifted and tilted at the same time, pump 1 2 provides the lifting action flow, and pump 2 3 provides the tilting action flow to realize a compound action.

[0031] When the engine or motor drives pump 1 2, pump 2 3 and pump 3 4 to rotate, when the electric control handle has no reversing action, pump 1 2 and pump 2 3 have no displacement output or work with a smaller standby displacement, the multi-way valve 5 is in the middle function, pump 1 2 and pump 2 3 suck oil from the oil tank 1, and the smaller standby oil output by pump 1 2 and pump 2 3 flows in through the inlet P1 and inlet P2 of the multi-way valve 5 respectively, and then flows through the valve core 1 501 and the valve core 2 502 respectively, and then merges and flows through the valve core 3 503 to the oil return port T1, and the outflowing oil flows through the return oil back pressure valve 6 and the return oil filter 16 in turn and returns to the oil tank 1. At the same time, pump 3 4 starts to work, sucks oil from the oil tank 1, bypasses the overflow valve 15 and supplies the pilot oil source valve 14, and the oil returns to the oil tank 1 after the bypass overflow.

[0032] When the electric control handle is pulled back to perform the bulldozer lifting action, at this time, valve six 509 is proportionally energized, and the pilot oil at this end face of valve core one 501 flows out through valve six 509 under reduced pressure. Valve core one 501 gradually switches to the lifting position a1 under the pressure difference between the two end faces, valve nine 512 (proportional) is energized, valve core three 503 gradually or quickly switches to the cut-off position c1, the solenoid valve in the load holding valve 7 is energized, and the pilot oil pushes the valve core of the load holding valve 7 open. Pump one 2 and pump two 3 are respectively proportionally energized to increase the displacement. The output pressure oil of pump one 2 enters through the inlet P1 of the multi-way valve 5, and the output pressure oil of pump two 3 enters through the inlet P2 of the multi-way valve 5, and then passes through the valve core two 502. After reaching the middle position, it flows through the lifting position a1 of the valve core 501 and then merges with the oil from the inlet P1. After the merging, it flows through the valve eleven 513 and flows through the lifting position a1 of the valve core 501, and then flows out through the working port Bl of the multi-way valve 5. The outflowing oil flows into the small chambers of the left lifting cylinder 10 and the right lifting cylinder 11 of the actuator to push the piston to move. At this time, the bulldozer is lifted, and the oil inside the large chambers of the left and right lifting cylinders flows out and merges. After passing through the load holding valve 7 of the multi-way valve 5, it flows through the lifting position a1 of the valve core 501 and then flows to the return oil port T1 of the multi-way valve 5. The oil flowing out of the return oil port T1 passes through the return oil back pressure valve 6 and then passes through the return oil filter 16 to flow back to the oil tank 1. When the piston inside the lifting cylinder is pushed by the oil to the vicinity of the upper end limit position, several buffer valves 17 on the pistons inside the two lifting cylinders are opened, and part of the high-pressure oil flows through these buffer valves 17 to the large chamber of the lifting cylinder. At this time, these buffer valves 17 play a role of stopping buffering, causing the cylinder piston to stop slowly, reducing the impact of the bulldozer being lifted to the limit position, and improving the operating comfort of the whole machine; during the process of the electric control handle being pulled back to the middle, valve six 509 loses power in proportion, valve core one 501 gradually returns to the middle position, valve nine 512 (proportional) loses power, valve core three 503 gradually returns to the default position c2 (connected position), the solenoid valve in the load holding valve 7 remains energized (delayed 1-2 seconds to lose power after returning to the middle position), pump one 2 and pump two 3 lose power in proportion to reduce displacement.

[0033] When the electric control handle is pushed forward to lower the bulldozer, at this time, valve 508 is proportionally energized, and the pilot oil at this end face of valve core 1 501 is reduced in pressure and flows out through valve 508. Valve core 1 501 gradually switches to the descending position a2 under the action of the pressure difference at both ends. Under the action of the deadweight load of the bulldozer push arm and the left and right tilt cylinders, the pressure oil inside the small chambers of the left and right lifting cylinders flows out and merges, then flows into through the working port 2 Bl of the multi-way valve 5, passes through the descending position a2 of the valve core 1 501, and flows to the return oil port T1 of the multi-way valve 5. The outflowing oil at the return oil port T1 passes through the return oil back pressure valve 6 and then passes through the return oil filter 16 to flow back to the oil tank 1. At the same time, valve nine 512 (proportional) is energized, valve core three 503 gradually or quickly switches to the cut-off position c1, the solenoid valve of the load holding valve 7 is energized, the pilot oil pushes the valve core of the load holding valve, pump one 2 and pump two 3 are energized proportionally to increase the displacement, the pressure oil output by pump one 2 enters through the inlet P1 of the multi-way valve 5, and the pressure oil output by pump two 3 enters through the inlet P2 of the multi-way valve 5. The pressure oil entering through the inlet P2 flows through the middle position of the valve core two 502 and then flows through the descending position a2 of the valve core one 501 to merge with the oil from the inlet P1. The combined pressure oil successively flows through valve eleven 513, the descending position a2 of the valve core one 501 and the load holding valve 7, and then flows out from the working port Al of the multi-way valve 5. The outflowing pressure oil then flows into the large chambers of the left lifting cylinder 10 and the right lifting cylinder 11 of the actuator to replenish the large chambers of the lifting cylinders. When the piston inside the lifting cylinder is pushed by the oil to near the limit position of the lower end, several buffer valves 17 on the pistons inside the two lifting cylinders gradually open, and part of the high-pressure oil flows through these buffer valves 17 to the large chamber of the lifting cylinder. At this time, these buffer valves 17 play a role of stopping and buffering, causing the cylinder piston to stop slowly, reducing the impact of the bulldozer descending to the limit position, and improving the operating comfort of the whole machine; during the process of pushing the electric control handle forward and pulling it back, at this time, valve five 508 loses power proportionally, valve core one 501 gradually returns to the middle position, valve nine 512 (proportional) loses power, valve core three 503 gradually returns to the default position c2, the solenoid valve of the load holding valve 7 remains energized (delayed 1-2 seconds to lose power after returning to the middle position), pump one 2 and pump two 3 lose power proportionally to reduce the displacement.

[0034] When the electric control handle is pushed forward past the hard point, the bulldozer will float and descend. At this time, valve five 508 obtains a floating current (generally the maximum current of the electric proportional pressure reducing valve), and the valve core one 501 moves and switches to the floating position a3 according to the pilot oil pressure difference at both ends. At this time, the large and small chambers of the lifting cylinder are connected and connected to the return oil, and the bulldozer descends. When the handle is pushed forward but not past the hard point, the action is performed according to the above-mentioned descending process. After passing the hard point and holding for 3-5s, the floating holding function is started (the handle automatically returns to the middle position after releasing the handle). At this time, valve five 508 obtains and maintains a floating current, the solenoid valve of the load holding valve 7 remains energized, and the pump is in standby state. The bulldozer is in floating or floating descending action. When the floating function is activated, the floating function can be interrupted by swinging the handle forward or backward again, and the normal descending or lifting action can be restored.

[0035] When the roller on the electric control handle rolls forward, the bulldozer tilts forward. At this time, valve seven 510 is proportionally energized, and valve core two 502 is switched to the lower position b2 due to the pilot oil pressure difference at both ends. The tilt valve is energized by the proportional valve XB (proportional), and the main valve core of the tilt valve 9 is switched to the right position d2. Pump two 3 is proportionally energized to increase the displacement. At this time, the pressure oil discharged by pump two 3 flows in through the inlet P2 of the multi-way valve 5, flows through the lower position b2 of the valve core two 502, and then flows out through the working port four Bt of the multi-way valve 5, and then flows into the left The piston of the left tilt cylinder 12 drives the piston rod to extend, and the oil in the small chamber of the left tilt cylinder 12 is pressed out. The pressed oil flows in through the oil port C of the tilt valve 9, and the oil flows out from the oil port A after passing through the right position d2 of the main valve core of the tilt valve 9, and then enters the large chamber of the right tilt cylinder 13. At this time, the left and right tilt cylinders extend at the same time, pushing the push shovel forward, and the oil in the small chamber of the right tilt cylinder 13 returns to the oil tank 1 after passing through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16. When the piston inside the left tilt cylinder 12 is pushed to the front end limit position, the buffer valve 17 on the piston gradually opens, the piston rod slowly stops, and the oil continues to pass through the buffer valve 17 and enters the small chamber of the cylinder, and then continues to pass through the tilt valve 9 to enter the large chamber of the right tilt cylinder 13, until the piston and piston rod of the right tilt cylinder 13 are pushed to the front end limit position, at which time the buffer valve 17 on the piston of the right tilt cylinder gradually opens, and the piston rod slowly stops. When the roller rolls back to the center, valve seven 510 proportionally loses power, valve core two 502 proportionally returns to the center position, the tilt valve proportional valve XB (proportional) loses power, the main valve core of the tilt valve 9 proportionally returns to the center position, and pump two 3 proportionally loses power to reduce the displacement.

[0036] When the roller on the electric control handle rolls backward, the bulldozer moves backward. At this time, valve 8 511 is proportionally energized, and valve core 2 502 is switched to the upper position b1 due to the pilot oil pressure difference at both ends. The proportional valve XB (proportional) on the tilt valve is energized, and the main valve core of the tilt valve 9 is switched to the right position d2. Pump 2 3 is proportionally energized to increase the displacement. At this time, the oil discharged from pump 2 3 flows in through the inlet P2 of the multi-way valve 5, flows through the upper position b1 of the valve core 2 502, and flows out through the working port 3 At of the multi-way valve 5. The outflowing oil flows in through the inlet P of the tilt valve 9. The oil passes After the main valve core of the tilt valve 9 is in the right position d2, it flows out from the oil port B and then enters the small chamber of the right tilt cylinder 13. The piston of the right tilt cylinder drives the piston rod to retract, and the oil in the large chamber of the right tilt cylinder is pressed out. The pressed oil flows in through the oil port A of the tilt valve 9. After the main valve core of the tilt valve 9 is in the right position d2, the oil flows out from the oil port C and then enters the small chamber of the left tilt cylinder 12. At this time, the left and right tilt cylinders retract at the same time, pulling the dozer backward. The oil in the large chamber of the left tilt cylinder returns to the oil tank 1 after passing through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16. When the piston inside the left tilt oil cylinder 12 is pushed to the rear end limit position, the buffer valve 17 on the piston gradually opens, the piston rod slowly stops, and the oil continues to pass through the buffer valve 17 and enters the small chamber of the oil cylinder, and then passes through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16, etc., and then returns to the oil tank 1, until the piston and piston rod of the right tilt oil cylinder 13 are pushed to the rear end limit position. At this time, the buffer valve on the piston of the right tilt oil cylinder gradually opens, and the piston rod slowly stops. During the roller rolling back to the middle, at this time, the valve 8 511 proportionally loses power, the valve core 2 502 proportionally returns to the middle position, the tilt valve power-on proportional valve XB (proportional) loses power, the main valve core of the tilt valve 9 proportionally returns to the middle position, and the pump 2 3 proportionally loses power to reduce the displacement.

[0037] The default state of the button on the back of the electric control handle can be set and selected on the screen. The screen can be set to the double-cylinder default mode when the button is not pressed. The tilt valve is powered on and the proportional valve remains de-energized, and the valve stem remains in the middle position. At this time, if the button is not pressed, the handle is swung left and right for the double cylinders to work together, and the dozer blade tilts to the left or right; after pressing the button (the tilt valve is powered on and the proportional valve XC is energized), the handle is swung left and right for single-cylinder action, and the dozer blade also tilts to the left or right.

[0038] The screen can be set to the single-cylinder default mode when the button is not pressed. The tilt valve is powered on and the proportional valve XC remains energized. At this time, if the button is not pressed, the left cylinder will act alone if the handle is swung left and right, and the dozer blade will tilt to the left or right. After pressing the button (the tilt valve is powered on and the proportional valve loses power, and the valve stem remains in the middle position), the double cylinders will act together if the handle is swung left and right, and the dozer blade will also tilt to the left or right.

[0039] When the setting button in the control screen is not pressed to set the double cylinder mode, when the electric control handle swings to the left, the bulldozer tilts to the left. At this time, valve 8 511 is proportionally energized, and valve core 2 502 is switched to the upper position b1 due to the pilot oil pressure difference at both ends. Pump 2 3 is proportionally energized to increase the displacement. At this time, the oil discharged from pump 2 3 flows in through the inlet P2 of the multi-way valve, flows through the upper position b1 of valve core 2 502, and flows out through the working port 3 At of the multi-way valve 5. The outflowing oil flows in through the inlet P of the tilt valve 9. The oil flows through the main After the valve core is in the middle position, it flows out from the oil port A and then enters the large chamber of the right tilt oil cylinder 13. The piston of the right tilt oil cylinder drives the piston rod to extend, and the oil in the small chamber of the right tilt oil cylinder is pressed out. The pressed oil flows in through the oil port B of the tilt valve 9. After the oil passes through the middle position of the main valve core of the tilt valve 9, it flows out from the oil port C and then enters the small chamber of the left tilt oil cylinder 12. At this time, the left tilt oil cylinder retracts, and the shovel tilts to the left. The oil in the large chamber of the left tilt oil cylinder returns to the oil tank 1 after passing through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16. During the process of the electric control handle returning to the middle, at this time, the valve 8 511 loses power in proportion, the valve core 2 502 returns to the middle position due to the pilot oil pressure difference at both ends, and the pump 2 3 loses power in proportion to reduce the displacement.

[0040] When the electric control handle swings to the right, the bulldozer tilts to the right. At this time, valve seven 510 is proportionally energized, and valve core two 502 is switched to the lower position b2 due to the pilot oil pressure difference at both ends. Pump two 3 is proportionally energized to increase the displacement. At this time, the oil discharged by pump two 3 flows in through the inlet P2 of the multi-way valve 5, passes through the lower position b2 of valve core two 502, and then flows out through the working port four Bt of the multi-way valve 5, and then flows into the large cavity of the left tilt cylinder 12. The piston of the left tilt cylinder drives the piston rod to extend, and the oil in the small cavity of the left tilt cylinder is pressed out. The pressed oil flows in through the oil port C of the tilt valve 9, and the oil flows out from the oil port B after passing through the right position d2 of the main valve core of the tilt valve 9, and then enters the small cavity of the right tilt cylinder 13. At this time, the left tilt cylinder 12 extends, the right tilt cylinder 13 retracts, and the bulldozer tilts to the right. The oil in the large cavity of the right tilt cylinder passes through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16 and then returns to the oil tank 1. During the process of the electric control handle returning to the center, at this time, valve seven 510 loses power in proportion, valve core two 502 returns to the center position due to the pilot oil pressure difference at both ends, and pump two 3 loses power in proportion to reduce the displacement.

[0041] When the setting button in the control screen is not pressed to set the dual-cylinder mode, press and hold the button on the back of the electric control handle (the proportional valve XC of the tilting valve is energized, and the main valve core of the tilting valve 9 is switched to the left position d1). At the same time, when the electric control handle swings to the left, the bulldozer tilts to the left. At this time, the valve eight 511 is proportionally energized, the valve core two 502 is switched to the upper position b1 due to the pilot oil pressure difference at both ends, and the pump two 3 is proportionally energized to increase the displacement. At this time, the oil discharged from the pump two 3 flows in through the inlet P2 of the multi-way valve 5, flows through the upper position b1 of the valve core two 502, and flows out through the working port three At of the multi-way valve 5. The outflowing oil flows in through the inlet P of the tilting valve 9, and the oil flows out from the oil port C after passing through the left position d1 of the main valve core of the tilting valve 9, and then enters the small cavity of the left tilting cylinder 12. The piston of the left tilting cylinder drives the piston rod to retract, and the oil in the large cavity of the left tilting cylinder is pressed out. The pressed oil returns to the oil tank 1 after passing through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16. During the process of the electric control handle returning to the center, at this time, valve eight 511 loses power in proportion, valve core two 502 returns to the center position due to the pilot oil pressure difference at both ends, and pump two 3 loses power in proportion to reduce the displacement.

[0042] When the setting button in the control screen is not pressed to set the dual-cylinder mode, press and hold the button on the back of the electric control handle (the proportional valve XC of the tilting valve is energized, and the main valve core of the tilting valve 9 is switched to the left position d1). At the same time, when the electric control handle swings to the right, the bulldozer tilts to the right. At this time, valve seven 510 is proportionally energized, and valve core two 502 is switched to the lower position b2 due to the pilot oil pressure difference at both ends. Pump two 3 is proportionally energized to increase the displacement. At this time, the oil discharged by pump two 3 flows in through the inlet P2 of the multi-way valve 5, flows through the lower position b2 of the valve core two 502, and then flows out through the working port four Bt of the multi-way valve 5, and then flows into the large cavity of the left tilting cylinder 12. The piston of the left tilting cylinder drives the piston rod to extend, and the oil in the small cavity of the left tilting cylinder is pressed out. The pressed oil flows in through the oil port C of the tilting valve 9, and the oil passes through the left position d1 of the main valve core of the tilting valve 9 and flows out from the inlet P, and then flows through the multi-way valve 5, the return oil back pressure valve 6 and the return oil filter 16, etc., and then returns to the oil tank 1. During the process of the electric control handle returning to the center, at this time, valve seven 510 loses power in proportion, valve core two 502 returns to the center position due to the pilot oil pressure difference at both ends, and pump two 3 loses power in proportion to reduce the displacement.

[0043] When controlling the lifting and lowering of the bulldozer, the control action is performed according to the above-mentioned lifting and lowering control logic. However, when controlling the left and right tilt cylinders during the lifting or lowering action, the left and right tilt control logic is superimposed for control. At this time, pump one is also controlled by the lifting or lowering control logic, and the flow is mainly supplied to the two lifting cylinders. Pump two needs to be controlled according to the left and right tilt control logic, and the flow is supplied to the left and right tilt cylinders after passing through the multi-valve tilt link and the tilt valve. At this time, a compound action is realized.

[0044] When controlling the movement of the left and right tilt cylinders, the control action is performed according to the above-mentioned left and right tilt control logic. However, when controlling the movement of the lifting cylinder while the left and right tilt cylinders are moving, the above-mentioned pushing up or lowering control logic control is superimposed. Pump 1 starts to change the displacement and supply oil according to the lifting or lowering control electrical signal. At the same time, the electric proportional valve of the lifting and lowering connecting valve in the multi-way valve is actuated, and the oil is supplied to the left and right lifting cylinders through the lifting and lowering connecting valve in the main multi-way valve to realize a compound action.

[0045] The present invention can realize that when the dozer is not in motion, the electric-controlled working pump does not output flow or outputs at a relatively small standby flow; when the dozer is lifted and lowered, the flow of the two pumps is combined through the electric-controlled multi-way valve and supplied to the lifting cylinder through the lifting link to execute the action; when the dozer is pitching forward or tilting left and right, the flow of one pump is supplied to the left and right tilting cylinders through the tilting link in the electric-controlled multi-way valve and the electric-controlled tilting valve to execute the action; through the coordinated action of the electric-controlled multi-way valve and the electric-controlled tilting valve, the left and right tilting cylinders can realize different connection modes, and the synchronous action of the left and right tilting cylinders can be realized when tilting left and right, and the synchronous proportional action of the left and right tilting cylinders can be realized when pitching forward and tilting backward. When the dozer is lifted and tilted at the same time, the flow of one of the electric-controlled pumps is supplied to the lifting cylinder through the multi-way valve to execute the action, and the flow of the other electric-controlled pump is supplied to the left and right tilting cylinders after passing through the tilting link of the multi-way valve and the electric-controlled tilting valve to execute the action, so as to realize the composite action of lifting and tilting the dozer. Users can freely switch operations according to the actual working conditions, which improves the flexibility of the shoveling action, enhances the adaptability of the whole machine to working conditions, and greatly improves work efficiency and energy utilization of the whole machine.

[0046] Embodiment 2 Based on the electronically controlled positive flow hydraulic system described in the first embodiment, this embodiment provides a bulldozer, wherein the bulldozer is equipped with the electronically controlled positive flow hydraulic system described in the first embodiment.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An electronically controlled positive flow hydraulic system, characterized in that: include: The outlets of pump 1 (2) and pump 2 (3) are connected to the inlet P1 and inlet P2 of the multi-way valve (5) respectively. Working port 1 of the multi-way valve (5) is connected to the large chamber of the lifting cylinder, working port 2 is connected to the small chamber of the lifting cylinder, working port 3 is connected to the small chambers of the right tilt cylinder (13) and the left tilt cylinder (12) through the tilt valve (9), and working port 4 is connected to the large chamber of the left tilt cylinder (12); When the bulldozer is not in motion, pump 1 (2) and pump 2 (3) do not output flow or output at a standby flow rate; when the bulldozer is lifted or lowered, pump 1 (2) and pump 2 (3) combine through a multi-way valve (5) to provide an operating flow rate; The multi-way valve (5) cooperates with the tilt valve (9) to achieve synchronous action of the left and right tilt cylinders when the dozer blade tilts left or right; synchronous proportional action of the left and right tilt cylinders when the dozer blade tilts forward or backward; and when the dozer blade lifts and tilts simultaneously, pump one (2) provides a lifting action flow rate, and pump two (3) provides a tilting action flow rate, thereby achieving a compound action.

2. The electronically controlled positive flow hydraulic system according to claim 1, characterized in that: The multi-way valve (5) comprises: The oil ports 1 of the valve core 1 (501) and the valve core 2 (502) are respectively connected to the inlet P1 and the inlet P2 of the multi-way valve (5); the oil ports 2 of the valve core 1 (501) and the valve core 2 (502) are both connected to the inlet of the valve core 3 (503); and the outlet of the valve core 3 (503) is connected to the oil return port of the multi-way valve (5); The oil port 4 of the valve core 1 (501) is connected to the inlet of the load holding valve (7), the outlet of the valve 1 (504), and the inlet of the valve 2 (505); the outlet of the load holding valve (7) is connected to the working port 1 of the multi-way valve (5); the inlet of the valve 1 (504) and the outlet of the valve 2 (505) are connected to the oil return port of the multi-way valve (5); the oil port 6 of the valve core 1 (501) is connected to the working port 2 of the multi-way valve (5); The oil port 4 of the valve core 2 (502) is connected to the working port 3 of the multi-way valve (5), and the oil port 6 is connected to the working port 4 of the multi-way valve (5).

3. The electronically controlled positive flow hydraulic system according to claim 2, characterized in that: The multi-way valve (5) further comprises: a third valve (506) connected between the inlet P1 of the multi-way valve (5) and the oil return port, and a fourth valve (507) connected between the inlet P2 of the multi-way valve (5) and the oil return port.

4. The electronically controlled positive flow hydraulic system according to claim 2, characterized in that: The multi-way valve (5) further comprises: a valve five (508) and a valve six (509) for controlling the switching of the valve core one (501), a valve seven (510) and a valve eight (511) for controlling the switching of the valve core two (502), and a valve nine (512) for controlling the switching of the valve core three (503); the inlets of the valves five (508) to nine (512) are all connected to the pilot port of the multi-way valve (5).

5. The electronically controlled positive flow hydraulic system according to claim 4, characterized in that: The tilt valve (9) comprises a valve core four (91) and a valve twelve (92) and a valve thirteen (93) for controlling the switching of the valve core four (91).

6. The electronically controlled positive flow hydraulic system according to claim 5, characterized in that: It also includes a pump three (4), the outlet of the pump three (4) is connected to the inlet of the pilot oil source valve (14) and the inlet of the relief valve (15), the outlet of the pilot oil source valve (14) is connected to the pilot ports of the multi-way valve (5) and the tilt valve (9) respectively; the outlet of the relief valve (15) is connected to the oil tank (1); the outlet of the pilot oil source valve (14) is connected to the pilot port of the load holding valve (7) through the valve ten (8).

7. The electronically controlled positive flow hydraulic system according to claim 1, characterized in that: The oil return port of the multi-way valve (5) is connected to the oil tank (1) via an oil return back pressure valve (6) and an oil return filter (16).

8. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer is not in motion, pump 1 (2) and pump 2 (3) output at a standby flow rate, the multi-way valve (5) is in the neutral position, and the pressure oil output by pump 1 (2) is discharged from the oil return port of the multi-way valve (5) through the inlet P1 of the multi-way valve (5), valve core 1 (501), and valve core 3 (503); the pressure oil output by pump 2 (3) is discharged from the oil return port of the multi-way valve (5) through the inlet P2 of the multi-way valve (5), valve core 2 (502), and valve core 3 (503); the pilot oil output by pump 3 (4) is discharged into the oil tank (1) through the overflow valve (15).

9. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer is lifted, valve six (509) is energized proportionally, and valve core one (501) is switched to the lifting position; valve nine (512) is energized, and valve core three (503) is switched to the cut-off position; the solenoid valve in the load holding valve (7) is energized, and the pilot oil pushes open the valve core of the load holding valve (7), and pump one (2) and pump two (3) are energized proportionally to increase the displacement, and the output pressure oil of pump one (2) enters through the inlet P1 of the multi-way valve (5), and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and then passes through the middle position of valve core two (502) and the lifting position of valve core one (501) and merges with the oil from inlet P1. After merging, it enters the lifting position of valve core one (501) through valve eleven (513), and then flows into the small chamber of the lifting cylinder through the working port two of the multi-way valve (5). At this time, the bulldozer is lifted.

10. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer is lowered, valve five (508) is proportionally energized, and valve core one (501) is switched to the lowered position; the pressure oil in the small chamber of the lifting cylinder flows out under the action of the deadweight of the bulldozer push arm and the tilt cylinder, and is discharged through the working port two of the multi-way valve (5) and the lowered position of valve core one (501); valve nine (512) is energized, and valve core three (503) is switched to the cut-off position; the solenoid valve in the load holding valve (7) is energized, and the pilot oil pushes open the valve core of the load holding valve (7), and pump one (2) and pump two (3) are operated. The two (3) are respectively energized in proportion to increase the displacement. The output pressure oil of pump one (2) enters through the inlet P1 of the multi-way valve (5), and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5). After passing through the middle position of valve core two (502) and the lowered position of valve core one (501), it merges with the oil from inlet P1. After merging, it enters the lowered position of valve core one (501) through valve eleven (513), and then flows into the large chamber of the lifting cylinder through the working port one of the multi-way valve (5). At this time, the bulldozer descends.

11. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer is lifted / lowered to the set limit position, the buffer valve arranged on the lifting cylinder piston opens to balance the pressure on both sides of the piston and play a buffering role.

12. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer floats and descends, valve five (508) receives floating current, and valve core one (501) switches to the floating position; the large and small chambers of the lifting cylinder are connected, and the bulldozer descends.

13. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the dozer blade tilts forward, valve seven (510) is proportionally energized, valve core two (502) is switched to the lower position, the tilt valve (9) is energized, the main valve core of the tilt valve (9) is switched to the right position, pump two (3) is proportionally energized to increase the displacement, the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the large chamber of the left tilt cylinder (12) through the lower position of valve core two (502) and the working port four of the multi-way valve (5), the pressure oil in the small chamber of the left tilt cylinder (12) enters the large chamber of the right tilt cylinder (13) through the right position of the tilt valve (9), the left tilt cylinder (12) and the right tilt cylinder (13) are extended at the same time, and the dozer blade tilts forward.

14. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the dozer blade is tilted backward, valve eight (511) is proportionally energized, valve core two (502) is switched to the upper position, the tilt valve (9) is energized, the main valve core of the tilt valve (9) is switched to the right position, pump two (3) is proportionally energized to increase the displacement, and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the small chamber of the right tilt cylinder (13) through the upper position of valve core two (502), the working port three of the multi-way valve (5), and the right position of the tilt valve (9). The pressure oil in the large chamber of the right tilt cylinder (13) enters the small chamber of the left tilt cylinder (12) through the right position of the tilt valve (9), and the left tilt cylinder (12) and the right tilt cylinder (13) are retracted at the same time, and the dozer blade is tilted backward.

15. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the dozer blade tilts forward / backward to the set limit position, the buffer valve arranged on the tilt cylinder piston opens to balance the pressure on both sides of the piston and play a buffering role.

16. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the dozer blade tilts to the left, valve eight (511) is proportionally energized, valve core two (502) is switched to the upper position, pump two (3) is proportionally energized to increase the displacement, and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the large chamber of the right tilt cylinder (13) through the upper position of valve core two (502), the working port three of the multi-way valve (5), and the middle position of the tilt valve (9). The pressure oil in the small chamber of the right tilt cylinder (13) enters the small chamber of the left tilt cylinder (12) through the middle position of the tilt valve (9), and the left tilt cylinder (12) retracts, and the dozer blade tilts to the left.

17. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the dozer blade tilts to the right, valve seven (510) is proportionally energized, valve core two (502) is switched to the lower position, pump two (3) is proportionally energized to increase the displacement, and the pressure oil output by pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the large chamber of the left tilt cylinder (12) through the lower position of valve core two (502) and the working port four of the multi-way valve (5). The pressure oil in the small chamber of the left tilt cylinder (12) enters the small chamber of the right tilt cylinder (13) through the middle position of the tilt valve (9), and the right tilt cylinder (13) retracts, and the dozer blade tilts to the right.

18. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer tilts to the left and the tilt valve (9) is switched to the left position, valve eight (511) is proportionally energized, valve core two (502) is switched to the upper position, pump two (3) is proportionally energized to increase the displacement, and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the small chamber of the left tilt cylinder (12) through the upper position of valve core two (502), the working port three of the multi-way valve (5), and the left position of the tilt valve (9), and the left tilt cylinder (12) retracts.

19. The electronically controlled positive flow hydraulic system according to claim 6, characterized in that: When the bulldozer tilts to the right and the tilt valve (9) is switched to the left position, valve seven (510) is proportionally energized, valve core two (502) is switched to the lower position, pump two (3) is proportionally energized to increase the displacement, and the output pressure oil of pump two (3) enters through the inlet P2 of the multi-way valve (5), and enters the large chamber of the left tilt cylinder (12) through the lower position of valve core two (502) and the working port four of the multi-way valve (5), and the left tilt cylinder (12) extends.

20. A bulldozer, characterized in that: The bulldozer is equipped with an electronically controlled positive flow hydraulic system as described in any one of claims 1 to 19.

Images