High-lift forklift, and hydraulic control system and method based on single-pump oil supply

Abstract

A high-lift forklift, and a hydraulic control system and method based on single-pump oil supply. The system comprises a load-sensitive pump (1), a hydraulic oil tank, a priority valve (3), an LS-type liquid filling valve (12), a steering gear (2), a brake valve (5), a brake accumulator (6), a first shuttle valve (13), and a second shuttle valve (11), wherein an oil outlet of the load-sensitive pump (1) is connected to each of a P port of the priority valve (3) and a P port of the LS-type liquid filling valve (12), a CF port of the priority valve (3) is connected to a P port of the steering gear (2), an EF port of the priority valve (3) is connected to a multy valve, and a port A of the LS type liquid filling valve (12) is connected to both the brake valve (5) and the brake accumulator (6); and an LS port of the LS-type liquid filling valve (12) is connected to a first shuttle valve (13), the first shuttle valve (13) is connected to each of an LS port of the priority valve (3), an LS port of the steering gear (2) and the second shuttle valve (11), and the second shuttle valve (11) is connected to an LS port of the load-sensitive pump (1). The problem of engine shutdown or failure when creating a pressure level required for normal operations caused by rapid pressure increments when oil liquid that is fed back by a steering system continuously drains at a medium position in a standby state is avoided.

Description

High-position forklift and hydraulic control system and method based on single pump oil supply

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 18, 2023, with application number 202311041287.8 and invention name “High-position forklift and hydraulic control system and method based on single pump oil supply”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of hydraulic control, and in particular relates to a high-position forklift and a hydraulic control system and method based on single-pump oil supply. Background Art

[0003] The hydraulic system of a high-position forklift truck generally consists of a travel system, an onboard multi-way valve system, a steering system, and a travel brake system. The travel system generally adopts an independent system of hydrostatic drive or torque converter. The steering system generally adopts an LS type (Load Senser) steering gear to control the steering movement of the axle, and the arm movement and outrigger movement are controlled by the onboard multi-way valve.

[0004] Travel braking is crucial to the safety of both equipment and personnel. While the equipment is moving, the system may need to simultaneously execute steering, travel braking, and the onboard multi-way valve. Currently, travel braking typically utilizes a charging valve + accumulator or a booster brake valve for service braking control. The charging valve + accumulator braking method includes two types: non-LS charging valves and LS charging valves.

[0005] For non-LS-type charging valve systems, a separate gear pump or a shared hydraulic pump with the engine cooling system typically charges the accumulator, with charging prioritized to ensure proper operation of the travel brake system. A separate hydraulic load-sensing pump supplies oil to the steering gear and the onboard multi-way valve, with flow distribution via a priority valve to prioritize steering flow, as shown in Figure 1. For rotary forklifts, this solution is unusable when the number of central swivel joint channels is limited, and may require the addition of an additional gear pump, increasing overall costs.

[0006] For the LS-type charging valve system, as shown in Figure 2, a single hydraulic load-sensing pump simultaneously supplies oil to the steering gear, LS-type charging valve, and the onboard multi-way valve. Flow distribution is achieved through a priority valve. Specifically, the priority valve's CF port (priority flow port) prioritizes oil flow to the steering gear and LS-type charging valve, while port EF (residual flow port) supplies oil to the onboard multi-way valve. The LS oil pressure (or load feedback oil pressure) of the onboard multi-way valve system, steering system, and service brake system is compared through a shuttle valve network and fed back to the load-sensing pump to achieve flow control. This approach solves the problem of a single pump supplying oil to three systems simultaneously and the limited number of center rotary joints. However, because the LS pressure (or load feedback pressure) of the LS-type charging valve must be fed back to the priority valve through the shuttle valve network, and the dynamic LS steering system requires continuous LS oil drain through the neutral position when in standby mode, LS oil pressure can accumulate during reverse flow through the shuttle valve network, leading to engine stall or a failure to build pressure in the charging system. This necessitates additional solenoid valves and sensors for detection and control, increasing system control complexity and the risk of failure.

[0007] The boost type brake valve is generally supplied with oil by a low-pressure oil circuit, and then the brake valve is pressurized to achieve driving braking. The boost type brake valve has a poor driving braking feel, and due to the boost cylinder, its own oil bag, etc., it has a large size and high requirements for installation space, resulting in limited installation.

[0008] Summary of the Invention

[0009] The present invention aims to provide a high-position forklift and a hydraulic control system and method based on single-pump oil supply to solve the problems of traditional LS-type filling valve systems, such as engine stalling caused by pressure buildup when LS oil flows reversely through the shuttle valve network, or the filling valve system's inability to build pressure, which increases the risk of system failure.

[0010] The present invention solves the above-mentioned technical problems through the following technical solutions: a hydraulic control system based on single-pump oil supply, comprising a load-sensing pump, a hydraulic oil tank, a priority valve, an LS-type liquid charging valve, a steering gear, a brake valve, a brake accumulator, and a pressure detection unit; the load-sensing pump is driven by a drive mechanism and its oil inlet is connected to the hydraulic oil tank, the oil outlet of the load-sensing pump is connected to the P port of the priority valve, the CF port of the priority valve is connected to the P port of the steering gear, the EF port of the priority valve is connected to the vehicle multi-way valve, and the A port of the LS-type liquid charging valve is connected to both the brake valve and the brake accumulator;

[0011] The system also includes a first shuttle valve and a second shuttle valve. The oil outlet of the load-sensing pump is also connected to the P port of the LS-type charging valve. The LS port of the LS-type charging valve is connected to the first shuttle valve. The first shuttle valve is simultaneously connected to the LS port of the priority valve, the LS port of the steering gear, and the second shuttle valve. The second shuttle valve is connected to the LS port of the load-sensing pump. The pressure detection unit is provided at the SW port of the LS-type charging valve and is used to detect the brake accumulator pressure.

[0012] Furthermore, the oil outlet of the load-sensing pump is connected to the P port of the LS-type filling valve through an overload protection valve and a pressure reducing valve in sequence; and the T port of the pressure reducing valve is connected to the hydraulic oil tank.

[0013] Furthermore, the overload protection valve is an electrically controlled valve or a hydraulically controlled valve. When the overload protection valve is an electrically controlled valve, the overload protection valve is an electromagnetic switch valve, an electromagnetic proportional valve or a servo valve.

[0014] Furthermore, the pressure reducing valve is a direct-acting pressure reducing valve or a pilot-operated pressure reducing valve. Furthermore, the LS type liquid filling valve is a single-circuit liquid filling valve or a dual-circuit liquid filling valve. When the LS type liquid filling valve is a single-circuit liquid filling valve, the brake valve is a single brake valve; when the LS type liquid filling valve is a dual-circuit liquid filling valve, the brake valve is a dual brake valve.

[0015] Furthermore, the steering gear, LS type filling valve and brake valve all have T ports, and the T ports of the steering gear, LS type filling valve and brake valve are all connected to the hydraulic oil tank.

[0016] Furthermore, the system also includes a controller and an alarm module connected to the controller. When the brake accumulator pressure is lower than the lower pressure limit set by the LS type charging valve and the brake accumulator is not charged, the alarm module is controlled to issue an alarm or limit the action while issuing the alarm.

[0017] Furthermore, the system further comprises a relief valve, and the oil outlet of the load-sensing pump is further connected to the hydraulic oil tank via the relief valve.

[0018] Based on the same concept, the present invention also provides a control method for the hydraulic control system based on single pump oil supply as described above, comprising:

[0019] The system starts and enters standby mode. When the brake accumulator pressure is lower than the lower pressure limit set by the LS-type charging valve, the load feedback pressure of the LS-type charging valve is fed back to the LS port of the load-sensing pump through the first and second shuttle valves. The displacement of the load-sensing pump changes and oil is directly charged into the brake accumulator through the LS-type charging valve. When the brake accumulator pressure reaches the upper pressure limit set by the LS-type charging valve, the LS-type charging valve is reversed, connecting the LS port of the load-sensing pump to the hydraulic oil tank, and the load-sensing pump returns to the low-pressure standby mode.

[0020] When the brake valve operates to reduce the pressure in the brake accumulator and drops below the lower pressure limit set by the LS charging valve, the LS charging valve switches direction, and the load feedback pressure of the LS charging valve is fed back to the LS port of the load sensing pump through the first shuttle valve and the second shuttle valve. The displacement of the load sensing pump changes and oil is directly charged into the brake accumulator through the LS charging valve.

[0021] When the steering gear is activated, or the boarding multi-way valve is activated, or the steering gear and the boarding multi-way valve are activated at the same time, the load feedback pressure of the steering gear and / or the boarding multi-way valve is fed back to the LS port of the load sensing pump through the first shuttle valve and the second shuttle valve. The load sensing pump supplies oil to the steering gear and / or the boarding multi-way valve through the priority valve, and the steering flow is given priority.

[0022] Furthermore, when the steering gear and / or the on-board multi-way valve is activated, causing the oil outlet pressure of the load-sensing pump to be higher than the upper pressure limit set by the LS-type charging valve, the oil outlet pressure of the load-sensing pump is reduced by the pressure reducing valve to charge the brake accumulator in real time, wherein the set pressure value of the pressure reducing valve is higher than the upper pressure limit set by the LS-type charging valve.

[0023] Based on the same concept, the present invention also provides a high-position forklift truck, comprising the hydraulic control system based on single-pump oil supply as described above. Beneficial effects

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] The present invention uses an LS-type charging valve and a load-sensing pump to simultaneously supply oil to the steering system, travel brake system, and onboard multi-way valve system. The priority valve and the LS-type charging valve are connected in parallel on the main oil line. The load-sensing pump directly supplies oil to the travel brake system without using the priority valve for flow distribution. The load feedback pressure of the LS-type charging valve is directly fed back to the load-sensing pump through the shuttle valve without the need for feedback to the priority valve. This avoids the problem of engine stalling or failure to build up pressure due to pressure buildup caused by continuous oil leakage from the steering system feedback oil in the neutral position in the standby state. It ensures that the brake accumulator always maintains brake reserve pressure without the need for additional detection components and control valves.

[0026] The priority valve only prioritizes flow distribution for the steering system and the on-board multi-way valve system, avoiding the problem of secondary flow priority distribution at the CF port of the priority valve; a pressure reducing valve and an overload protection valve are added before the LS-type filling valve to avoid malfunction or failure of the travel brake system caused by excessive filling pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] FIG1 is a hydraulic principle diagram of a non-LS type filling valve system in the background art of the present invention;

[0029] FIG2 is a hydraulic principle diagram of an LS type filling valve system in the background art of the present invention;

[0030] FIG3 is a hydraulic principle diagram of a hydraulic control system according to an embodiment of the present invention; wherein the solid line represents the main oil circuit and the dotted line represents the load feedback oil circuit;

[0031] FIG4 is a liquid filling path according to an embodiment of the present invention;

[0032] FIG5 is a diagram of the feedback oil path in an embodiment of the present invention.

[0033] Among them, 1-load sensing pump, 2-steering gear, 3-priority valve, 4-charging valve, 5-brake valve, 6-brake accumulator, 7-pressure detection unit, 8-overflow valve, 9-hydraulic oil tank, 10-gear pump, 11-second shuttle valve, 12-LS type charging valve, 13-first shuttle valve, 14-overload protection valve, 15-pressure reducing valve. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0035] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0036] As shown in FIG3 , a hydraulic control system based on single-pump oil supply provided in this embodiment includes a load-sensing pump 1, a hydraulic oil tank, a priority valve 3, an LS-type charging valve 12, a steering gear 2, a brake valve 5, a brake accumulator 6, a first shuttle valve 13, a second shuttle valve 11, and a pressure detection unit 7. The load-sensing pump 1 is driven by a drive mechanism and its oil inlet is connected to the hydraulic oil tank. The oil outlet of the load-sensing pump 1 is simultaneously connected to the P port (i.e., the oil inlet) of the priority valve 3 and the P port of the LS-type charging valve 12. The CF port (i.e., the priority flow port) of the priority valve 3 is connected to the P port of the steering gear 2. The EF port (i.e., the residual flow port) of the priority valve 3 is connected to the on-board multi-way valve, and the A port (i.e., the filling oil outlet) of the LS-type charging valve 12 is simultaneously connected to the brake valve 5 and the brake accumulator 6; the LS port (i.e., the load feedback oil port) of the LS-type charging valve 12 is connected to the first shuttle valve 13, and the first shuttle valve 13 is simultaneously connected to the LS port of the priority valve 3, the LS port of the steering gear 2 and the second shuttle valve 11, and the second shuttle valve 11 is connected to the LS port of the load-sensing pump 1; the pressure detection unit 7 is arranged at the SW port (i.e., the pressure detection port) of the LS-type charging valve 12 and is used to detect the pressure of the brake accumulator 6.

[0037] The hydraulic control system of the present invention utilizes an LS charging valve, a load-sensing pump 1, and a priority valve 3 to supply oil to the steering gear 2, brake valve 5, and onboard multi-way valve. The load-sensing pump 1 directly supplies oil to the travel brake system without passing through the priority valve 3. Flow distribution between the steering system and the onboard multi-way valve system is achieved through the priority valve 3, ensuring steering flow priority. The charging path is shown in Figure 4. Load feedback pressure from the LS charging valve 12, steering gear 2, and onboard multi-way valve is fed back to the load-sensing pump 1 via the first shuttle valve 13 and the second shuttle valve 11. The load feedback pressure from the LS charging valve 12 does not need to be fed back to the priority valve 3, achieving pressure and flow distribution control. The feedback oil path is shown in Figure 5.

[0038] In this embodiment, as shown in Figure 3, the oil outlet of the load-sensing pump 1 is connected to the P port of the LS-type charging valve 12 via an overload protection valve 14 and a pressure-reducing valve 15. The T port of the pressure-reducing valve 15 is connected to the hydraulic oil tank. The overload protection valve 14 and the pressure-reducing valve 15 are added before the P port of the LS-type charging valve 12. The pressure-reducing valve 15 prevents excessive charging pressure from causing malfunction or failure of the travel brake system. When the pressure in the brake accumulator 6 exceeds the safety setpoint of the charging circuit, the overload protection valve 14 is controlled to close, isolating the charging circuit from the main oil circuit. The pressure detection unit 7 monitors the charging circuit pressure in real time, ensuring the safety and reliability of the system.

[0039] In this embodiment, the overload protection valve 14 can be an electrically controlled valve, such as a solenoid on / off valve, solenoid proportional valve, or servo valve, or a hydraulically controlled valve. When the overload protection valve 14 is an electrically controlled valve, a controller controls the closing of the overload protection valve 14 based on the pressure of the brake accumulator 6 and the safety setpoint of the charging circuit. The overload protection valve 14 can be a two-position valve or a three-position valve (meaning the valve core has two or three different operating positions); the overload protection valve 14 can also be a two-way valve, a three-way valve, or a four-way valve (meaning the valve body has two, three, or four ports that can be connected to different oil pipes or gas systems). In this embodiment, the pressure reducing valve 15 is a direct-acting pressure reducing valve or a pilot-operated pressure reducing valve.

[0040] In this embodiment, the pressure detection unit 7 is a pressure sensor or a pressure switch.

[0041] In this embodiment, the LS-type charging valve 12 is a single-circuit charging valve or a dual-circuit charging valve. When the LS-type charging valve 12 is a single-circuit charging valve, the brake valve 5 is a single brake valve corresponding to one brake accumulator 6. When the LS-type charging valve 12 is a dual-circuit charging valve, the brake valve 5 is a dual brake valve corresponding to two brake accumulators 6. As shown in Figure 3, port A1 of the LS-type charging valve 12 is simultaneously connected to one brake accumulator 6 and the brake valve 5, and port A2 is simultaneously connected to the other brake accumulator 6 and the brake valve 5. The brake accumulator 6 provides brake pressure oil to the brake mechanism through the brake valve 5.

[0042] In this embodiment, the steering gear 2, LS-type filling valve 12, and brake valve 5 all have T-ports (i.e., safety valve oil return ports), which are connected to the hydraulic oil tank. The hydraulic control system of the present invention also includes a relief valve 8, through which the oil outlet of the load-sensing pump 1 is also connected to the hydraulic oil tank.

[0043] In this embodiment, the system also includes a controller and an alarm module connected to the controller. When the pressure of the brake accumulator 6 detected by the pressure detection unit 7 is lower than the lower pressure limit set by the LS-type filling valve 12 and the brake accumulator 6 is not filled, the controller controls the alarm module to issue an alarm, or restrict related actions while issuing an alarm, for example, if the pressure is insufficient and the brake fails, the walking action is restricted.

[0044] This embodiment further provides a control method for the hydraulic control system based on single-pump oil supply as described above, comprising:

[0045] (1) When the high-position forklift truck starts and is on standby, when the pressure of the brake accumulator 6 is lower than the lower pressure limit set by the LS type charging valve 12, the load feedback pressure of the LS type charging valve 12 is fed back to the LS port of the load sensing pump 1 through the first shuttle valve 13 and the second shuttle valve 11, and the load sensing pump 1 directly charges the brake accumulator 6 through the LS type charging valve 12; when the pressure of the brake accumulator 6 reaches the upper pressure limit set by the LS type charging valve 12, the LS type charging valve 12 is reversed, so that the LS port of the load sensing pump 1 is connected to the hydraulic oil tank, the filling is completed, and the load sensing pump 1 returns to the low-pressure standby state.

[0046] (2) The operation of the service brake valve 5 causes the pressure of the brake accumulator 6 to drop. When the pressure of the brake accumulator 6 drops below the lower pressure limit set by the LS-type charging valve 12, the load-sensing pump 1 directly charges the brake accumulator 6 through the LS-type charging valve 12. Based on the pressure of the brake accumulator 6 and the lower and upper pressure limits set by the LS-type charging valve 12, the automatic circulation charging action of the brake accumulator 6 is realized, ensuring that the brake accumulator 6 always maintains the brake reserve pressure.

[0047] (3) When the steering gear 2 is actuated, or the onboard multi-way valve is actuated, or the steering gear 2 and the onboard multi-way valve are actuated simultaneously, the load feedback pressure of the steering gear 2 and / or the onboard multi-way valve is fed back to the LS port of the load sensing pump 1 through the first shuttle valve 13 and the second shuttle valve 11. The load sensing pump 1 supplies oil to the steering gear 2 and / or the onboard multi-way valve through the priority valve 3, and distributes the flow through the priority valve 3, ensuring that the steering gear 2 has priority flow. When multiple actions are performed simultaneously, steering and brake filling take priority.

[0048] (4) When the steering gear 2 and / or the onboard multi-way valve is actuated, causing the oil outlet pressure of the load-sensing pump 1 to be higher than the upper pressure limit set by the LS-type filling valve 12, the oil outlet pressure of the load-sensing pump 1 can be reduced by the pressure reducing valve 15 to charge the brake accumulator 6 in real time and ensure that the pressure value of the brake accumulator 6 is within a safe value range. The set pressure value of the pressure reducing valve 15 is slightly higher than the upper pressure limit set by the LS-type filling valve 12.

[0049] (5) When the pressure reducing valve 15 fails and the pressure of the brake accumulator 6 detected by the pressure detection unit 7 is higher than the safety setting value of the filling circuit, the overload protection valve 14 is controlled to close, cutting off the filling circuit from the main oil circuit to ensure the safety of the filling circuit.

[0050] The present invention uses a load-sensing pump 1 to simultaneously supply oil to the steering system, the travel brake system, and the onboard multi-way valve system, eliminating a separate power source for the liquid filling circuit, simplifying the liquid filling circuit and piping, saving two center rotary joint channels for the rotary forklift, and reducing overall costs.

[0051] In the present invention, the load-sensing pump 1 directly supplies oil to the travel brake system without distributing the flow through the priority valve 3. The load feedback pressure of the LS-type charging valve 12 is directly fed back to the load-sensing pump 1 through the shuttle valve, and does not need to be fed back to the priority valve 3. This avoids the problem of engine stalling or failure to build up pressure caused by the steering system feedback oil continuously leaking at the neutral position in the standby state, and ensures that the brake accumulator 6 always maintains the brake reserve pressure without adding additional detection elements and control valves.

[0052] The above disclosure is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, and they should all be covered by the scope of protection of the present invention.

Claims

1. A hydraulic control system based on single pump oil supply, comprising a load sensing pump, a hydraulic oil tank, a priority valve, an LS type filling valve, a steering gear, a brake valve, a brake accumulator and a pressure detection unit; the load sensing pump is driven by a driving mechanism and its oil inlet is connected to the hydraulic oil tank, the oil outlet of the load sensing pump is connected to the P port of the priority valve, the CF port of the priority valve is connected to the P port of the steering gear, the EF port of the priority valve is connected to the multi-way valve on the vehicle, and the A port of the LS type filling valve is connected to the brake valve and the brake accumulator at the same time; characterized in that: The system also includes a first shuttle valve and a second shuttle valve. The oil outlet of the load-sensing pump is also connected to the P port of the LS-type filling valve. The LS port of the LS-type filling valve is connected to the first shuttle valve. The first shuttle valve is simultaneously connected to the LS port of the priority valve, the LS port of the steering gear and the second shuttle valve. The second shuttle valve is connected to the LS port of the load-sensing pump. The pressure detection unit is arranged at the SW port of the LS-type filling valve and is used to detect the pressure of the brake accumulator.

2. The hydraulic control system based on single pump oil supply according to claim 1, characterized in that: The oil outlet of the load-sensing pump is connected to the P port of the LS-type filling valve through an overload protection valve and a pressure reducing valve in sequence; the T port of the pressure reducing valve is connected to the hydraulic oil tank.

3. The hydraulic control system based on single pump oil supply according to claim 2, characterized in that: The overload protection valve is an electrically controlled valve or a hydraulically controlled valve. When the overload protection valve is an electrically controlled valve, the overload protection valve is an electromagnetic switch valve, an electromagnetic proportional valve or a servo valve.

4. The hydraulic control system based on single pump oil supply according to claim 2, characterized in that: The pressure reducing valve is a direct-acting pressure reducing valve or a pilot-operated pressure reducing valve.

5. The hydraulic control system based on single pump oil supply according to claim 1, characterized in that: The LS type filling valve is a single-circuit filling valve or a double-circuit filling valve. When the LS type filling valve is a single-circuit filling valve, the brake valve is a single brake valve; when the LS type filling valve is a double-circuit filling valve, the brake valve is a double brake valve.

6. The hydraulic control system based on single pump oil supply according to claim 1, characterized in that: The steering gear, the LS type filling valve and the brake valve all have T ports, and the T ports of the steering gear, the LS type filling valve and the brake valve are all connected to the hydraulic oil tank.

7. The hydraulic control system based on single pump oil supply according to claim 1, characterized in that: The system also includes a controller and an alarm module connected to the controller. When the pressure of the brake accumulator is lower than the lower pressure limit set by the LS type filling valve and the brake accumulator is not filled, the alarm module is controlled to issue an alarm or limit the action while issuing the alarm.

8. A control method for a hydraulic control system based on single-pump oil supply according to any one of claims 1 to 7, comprising: The system starts and is in standby mode. When the pressure of the brake accumulator is lower than the lower pressure limit set by the LS type charging valve, the load feedback pressure of the LS type charging valve is fed back to the LS port of the load sensing pump through the first shuttle valve and the second shuttle valve. The displacement of the load sensing pump changes and directly charges the brake accumulator through the LS type charging valve. When the pressure of the brake accumulator reaches the upper pressure limit set by the LS type charging valve, the LS type charging valve is reversed to connect the LS port of the load sensing pump to the hydraulic oil tank, and the load sensing pump returns to the low-pressure standby state. When the brake valve works to reduce the pressure in the brake accumulator and drops below the lower pressure limit set by the LS type charging valve, the LS type charging valve changes direction, and the load feedback pressure of the LS type charging valve is fed back to the LS port of the load sensing pump through the first shuttle valve and the second shuttle valve. The displacement of the load sensing pump changes and directly charges the brake accumulator through the LS type charging valve. When the steering gear is activated, or the boarding multi-way valve is activated, or the steering gear and the boarding multi-way valve are activated at the same time, the load feedback pressure of the steering gear and / or the boarding multi-way valve is fed back to the LS port of the load sensing pump through the first shuttle valve and the second shuttle valve, and the load sensing pump supplies oil to the steering gear and / or the boarding multi-way valve through the priority valve, and the steering flow is given priority.

9. The control method of the hydraulic control system based on single pump oil supply according to claim 8, characterized in that: When the steering gear and / or the multi-way valve on the vehicle is actuated, making the oil outlet pressure of the load sensing pump higher than the upper pressure limit set by the LS type charging valve, the oil outlet pressure of the load sensing pump is reduced by the pressure reducing valve to charge the brake accumulator in real time, wherein the set pressure value of the pressure reducing valve is higher than the upper pressure limit set by the LS type charging valve.

10. A high-position forklift, characterized in that: It comprises a hydraulic control system based on single pump oil supply as described in any one of claims 1 to 7.

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