An energy-saving hydraulic system and a loader

Abstract

The present invention discloses an energy-saving hydraulic system and a loader. The hydraulic system includes a hydraulic oil tank, a steering gear pump, a working gear pump assembly, a priority valve, a one-way unloading valve, etc. The EF ports of the priority valve are connected to the inlet port of the multi-way valve through a one-way unloading valve. When the working hydraulic system is in a high-pressure and low-flow condition or a high-pressure overflow condition, the excess oil in the steering hydraulic system that merges into the working hydraulic system can be unloaded through the one-way unloading valve, avoiding the energy loss and system heating caused by the high-pressure overflow of the steering hydraulic system. The gear pump in the working gear pump assembly sucks oil from the hydraulic oil tank through a variable throttle valve, and returns to the hydraulic oil tank through a speed sensing control valve and a low-pressure overflow valve when there is no load signal. The gear pump no longer provides flow to the multi-way valve, thus greatly reducing the energy loss of the system. Based on the speed sensing control valve, it realizes automatic matching of the lubricating oil suction flow of the pump according to the speed change of the working gear pump, reduces energy consumption, and ensures the reliability of the use of the gear pump.

Description

Technical Field

[0001] The present invention relates to an energy-saving hydraulic system and a loader, belonging to the technical field of construction machinery. Background Art

[0002] The hydraulic system of a loader generally mainly consists of a working hydraulic system and a steering hydraulic system. The working hydraulic system generally consists of a working pump, a multi-way valve, working hydraulic cylinders and their pipelines; the steering hydraulic system generally consists of a steering pump, a priority valve, a steering gear and their pipelines. In the prior art, the most widely installed hydraulic system for loaders is still a fixed-displacement system, that is, external meshing gear pumps with fixed displacements are used as the working pump and the steering pump. Due to advantages such as low price, reliable use, and low requirements for the cleanliness of the oil, it has been widely used in construction machinery.

[0003] Based on the principle of the fixed-displacement system, when applied to loaders of different tonnages, its application forms are slightly different, and are roughly divided into the following two types:

[0004] Solution 1: A non-confluent working and steering system, that is, the working pump supplies oil to the working hydraulic cylinders in the working device alone, and the steering pump supplies oil to the steering cylinders alone;

[0005] Solution 2: A confluent working and steering system, that is, the steering pump supplies oil to the steering cylinders alone, and the excess flow is confluent with the working pump to supply the working hydraulic cylinders in the working device. Among them, in the single-pump flow-splitting hydraulic system applied to small loaders, the working pump and the steering pump are the same pump, which preferentially supplies oil to the steering system, and the excess flow supplies oil to the working system. This system is actually also a confluent working and steering system.

[0006] Based on the above two application forms of the fixed-displacement system, whether confluent or not, in order to solve problems such as heavy steering during engine idling, the displacement of the steering pump cannot be too small, so when the engine is running at high speed, the energy loss will be very large; on the contrary, for the fixed-variable confluent system and the full-variable hydraulic system using variable pumps in the steering system, although the flow can be matched as needed, the use and maintenance costs of the variable pump are relatively high, the system is also more complex, and while achieving the energy-saving effect, the cost advantage and the convenience of maintenance are lost. Summary of the Invention

[0007] To solve the deficiencies of the prior art, the purpose of the present invention is to provide an energy-saving hydraulic system and a loader, which solve the problems of low working efficiency and large energy loss in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions:

[0009] An energy-saving hydraulic system, comprising a hydraulic oil tank, a steering gear pump, a working pump assembly, a working hydraulic cylinder, a steering hydraulic cylinder and a priority valve. The working pump assembly includes a gear pump, a rotational speed sensing control valve, a low-pressure relief valve, a variable throttle valve, a first reversing valve, a second reversing valve, a working oil port P4 and a suction port T2.

[0010] The inlet of the steering gear pump is communicated with the hydraulic oil tank. The outlet of the steering gear pump is connected to the inlet port P of the priority valve. The first working oil port CF of the priority valve supplies oil to the steering hydraulic cylinder, and the second working oil port EF of the priority valve supplies oil to the working hydraulic cylinder.

[0011] The suction port T2 of the working pump assembly is communicated with the hydraulic oil tank. The working oil port P4 of the working pump assembly supplies oil to the working hydraulic cylinder.

[0012] The suction port T2 of the working pump assembly is connected to the suction port T1 of the gear pump through the variable throttle valve. The outlet of the gear pump is connected to the inlet end of the second reversing valve. The first outlet end of the second reversing valve is connected to the Q1 oil port of the rotational speed sensing control valve. The second outlet end of the second reversing valve is connected to the working oil port P4. The control oil port LS1 of the second reversing valve is connected to the working oil port P4.

[0013] The P2 oil port of the rotational speed sensing control valve is communicated with the hydraulic oil tank through the low-pressure relief valve. The P3 oil port of the rotational speed sensing control valve is connected to the control oil port of the variable throttle valve.

[0014] The inlet end and the outlet end of the first reversing valve are respectively connected to both ends of the variable throttle valve. The control oil port LS2 of the first reversing valve is connected to the working oil port P4.

[0015] Further, the aforementioned working pump assembly further includes a check valve. The inlet of the check valve is connected to the second outlet end of the second reversing valve, and the outlet of the check valve is connected to the working oil port P4.

[0016] Further, the aforementioned further includes a multi-way valve, a pilot oil source valve and a pilot valve.

[0017] The multi-way valve includes an inlet port P, a first working port, a second working port, pilot oil ports a1, b1, a2, b2 and a return port T. The inlet port P is connected to the working oil port P4 of the working pump assembly. The first working port and the second working port are respectively communicated with different working hydraulic cylinders. The return port T of the multi-way valve is connected to the hydraulic oil tank.

[0018] The inlet port P1 of the pilot oil source valve is connected to the outlet of the steering gear pump. The outlet U of the pilot oil source valve is connected to the inlet port P of the pilot valve. The return port T of the pilot oil source valve is connected to the hydraulic oil tank. The outlet ports 1a, 1b, 2a, 2b of the pilot valve are respectively connected to the corresponding pilot oil ports a1, b1, a2, b2 of the multi-way valve.

[0019] Further, the foregoing also includes a steering gear and a one-way unloading valve;

[0020] The first working oil port CF of the priority valve is connected to the oil inlet of the steering gear. The second working oil port EF of the priority valve is connected to the oil inlet of the multi-way valve through a one-way unloading valve, and the unloading port of the one-way unloading valve is communicated with the hydraulic oil tank;

[0021] The number of steering hydraulic cylinders is two. The rodless cavity of the first steering hydraulic cylinder is communicated with the R port of the steering gear, and the rod chamber is communicated with the L port of the steering gear. The rodless cavity of the second steering hydraulic cylinder is communicated with the L port of the steering gear, and the rod chamber is communicated with the R port of the steering gear.

[0022] Further, the foregoing also includes a radiator and a filter disposed between the return port T of the multi-way valve and the hydraulic oil tank.

[0023] Further, the foregoing hydraulic oil tank is a pre-pressurized hydraulic oil tank with an exhaust pre-pressurized air filter.

[0024] Further, the foregoing multi-way valve is a pilot control open center multi-way valve.

[0025] Further, the foregoing pilot valve is a hydraulically controlled pilot valve.

[0026] Further, the foregoing steering gear is a load sensing full hydraulic steering gear.

[0027] A wheel loader applies the energy-saving hydraulic system according to any one of the foregoing.

[0028] The beneficial effects achieved by the present invention:

[0029] 1. The working pump assembly composed of integrating a variable throttle valve and a speed sensing control valve at the oil inlet and outlet of the gear pump respectively. When the working oil cylinder has no action, the working gear pump can be in a small flow self-lubrication state, solving the energy loss problem caused by the working gear pump returning oil through the middle position of the multi-way valve during the transfer of the wheel loader; and based on the speed sensing control valve, it can automatically match the lubricating oil suction flow of the pump according to the speed change of the working gear pump, further reducing energy consumption while ensuring the reliability of the gear pump.

[0030] 2. By adopting a one-way unloading valve, when the working hydraulic system is in a high-pressure small-flow working condition or a high-pressure overflow working condition, the excess oil in the steering hydraulic system flowing into the working hydraulic system can be unloaded through the one-way unloading valve, avoiding the energy waste caused by the high pressure of the steering hydraulic system. Description of the Drawings

[0031] Figure 1 is the schematic diagram of the hydraulic system of the present invention;

[0032] Figure 2It is an enlarged structural schematic diagram of the working pump assembly of the present invention;

[0033] Figure 3 It is a schematic diagram of the power flow transmission route of the rotational speed sensing control valve of the present invention.

[0034] The meanings of the reference numerals in the figure: 1 - hydraulic oil tank; 2 - steering gear pump; 3 - working pump assembly; 4 - multi-way valve; 5 - working hydraulic cylinder; 6 - pilot valve; 7 - steering hydraulic cylinder; 8 - steering gear; 9 - priority valve; 10 - one-way unloading valve; 11 - hydraulic oil cooler; 12 - return oil filter; 13 - pilot oil source valve; 14 - gear pump; 15 - rotational speed sensing control valve; 16 - low-pressure overflow valve; 17 - variable throttle valve; 18 - first reversing valve; 19 - second reversing valve; 20 - one-way valve. Specific embodiments

[0035] The technical solution of the present invention will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0036] Embodiment 1

[0037] This embodiment discloses an energy-saving hydraulic system, as Figure 1 shown, including a hydraulic oil tank 1, a steering gear pump 2, a working pump assembly 3, a multi-way valve 4, a working hydraulic cylinder 5, a pilot valve 6, a steering hydraulic cylinder 7, a steering gear 8, a priority valve 9, a one-way unloading valve 10, a hydraulic oil cooler 11, a return oil filter 12 and a pilot oil source valve 13.

[0038] The hydraulic oil tank 1 is a pre-pressurized hydraulic oil tank, with an exhaust pre-pressurized air filter. While filtering the air entering the tank, it can keep a certain positive air pressure inside the tank with the change of the liquid level in the hydraulic oil tank, ensuring reliable oil supply to the steering gear pump 2 and the working pump assembly 3.

[0039] The inlet of the steering gear pump 2 and the inlet of the working pump assembly 3 are both connected to the hydraulic oil tank 1.

[0040] The oil inlet P of the priority valve 9 is connected to the oil outlet of the steering gear pump 2. The first working oil port CF of the priority valve 9 is connected to the oil inlet of the steering gear 8, and hydraulic fluid is provided to the steering hydraulic cylinder 7 through the steering gear 8. The second working oil port EF of the priority valve 9 is connected to the oil inlet of the multi-way valve 4 through the one-way unloading valve 10, and excess hydraulic fluid is provided to the working hydraulic cylinder 5 through the multi-way valve 4. When the pressure at the oil inlet of the multi-way valve 4 reaches the set pressure of the one-way unloading valve 10, the working hydraulic system is in a high-pressure and low-flow state, and the hydraulic fluid provided by the steering gear pump 2 to the working hydraulic cylinder 5 through the EF port of the priority valve 9 flows back to the hydraulic oil tank 1 through the unloading port of the one-way unloading valve 10, avoiding energy waste caused by high pressure in the steering hydraulic system.

[0041] The steering gear 8 is a load-sensing full-hydraulic steering gear; the steering gear 8 has a first state that makes the piston rod of the steering hydraulic cylinder 7 extend and a second state that makes the piston rod of the steering hydraulic cylinder 7 retract. As Figure 1 shown, the rodless cavity of one of the steering hydraulic cylinders is connected to the R port of the steering gear 8, and the rod chamber is connected to the L port of the steering gear 8; the rodless cavity of the other steering hydraulic cylinder is connected to the L port of the steering gear 8, and the rod chamber is connected to the R port of the steering gear 8. Therefore, when the piston rod of one of the steering hydraulic cylinders extends, the piston rod of the other steering hydraulic cylinder retracts, and the two steering hydraulic cylinders cooperate to drive the wheels to steer. The speed of movement of the steering hydraulic cylinder 7 is controlled by the input of the steering gear 8.

[0042] The multi-way valve 4 is an open-center multi-way valve; the multi-way valve 4 has an oil inlet P port, a first working port, a second working port, pilot oil ports a1 port, b1 port, a2 port, b2 port, and a return port T port; the first working port of the multi-way valve 4 is connected to the first working hydraulic cylinder, the second working port of the multi-way valve 4 is connected to the second working hydraulic cylinder, and the return port T of the multi-way valve 4 is connected to the hydraulic oil tank 1 through an oil return pipeline.

[0043] Each working port of the multi-way valve 4 is respectively connected to the corresponding working hydraulic cylinder 5, and the working hydraulic cylinder 5 is used to drive the operation components to move; the loader bucket can perform actions such as lifting the arm, lowering the arm, closing the bucket, and discharging materials.

[0044] The hydraulic system also includes a pilot oil source valve 13 and a pilot valve 6. The oil inlet P1 of the pilot oil source valve 13 is connected to the oil outlet of the steering gear pump 2; the oil outlet U of the pilot oil source valve 13 is connected to the oil inlet P of the pilot valve 6; the oil return port T of the pilot oil source valve 13 is connected to the hydraulic oil tank 1; the oil outlets 1a port, 1b port, 2a port, and 2b port of the pilot valve 6 are respectively connected to the corresponding pilot oil ports a1 port, b1 port, a2 port, and b2 port of the multi-way valve 4, and are used to control the switching of the working state of the multi-way valve 4.

[0045] The hydraulic system also includes a radiator 11 and a filter 12 arranged in the pipeline between the return port T of the multi-way valve 4 and the hydraulic oil tank 1.

[0046] The hydraulic system further includes a working pump assembly 3, Figure 2 An enlarged view of the working pump assembly 3 is shown, in combination with Figure 1 and Figure 2 As shown, the working pump assembly 3 includes a gear pump 14, a rotational speed sensing control valve 15, a low-pressure overflow valve 16, a variable throttle valve 17, a first reversing valve 18, a second reversing valve 19, and a check valve 20; the working pump assembly 3 includes a working oil port P4 and a suction port T2; the working oil port P4 of the working pump assembly 3 is connected to the oil inlet of the multi-way valve 4, and hydraulic fluid is provided to the working hydraulic cylinder 5 through the multi-way valve 4. The suction port T2 of the working pump assembly 3 is connected to the pre-pressure hydraulic oil tank 1.

[0047] The first reversing valve 18 has a first position and a second position. One end of the first reversing valve 18 is a spring with a spring force of ΔP2, and the other end is composed of control oil LS2. The control oil LS2 of the first reversing valve 18 is connected to the working oil port P4 of the working pump assembly 3.

[0048] The second reversing valve 19 has a first position and a second position. One end of the second reversing valve 19 is a spring with a spring force of ΔP1, and the other end is composed of control oil LS1. The control oil LS1 of the second reversing valve 19 is connected to the working oil port P4 of the working pump assembly 3.

[0049] The P2 oil port of the rotational speed sensing control valve 15 is connected to the hydraulic oil tank 1 through the low-pressure overflow valve 16. The rotational speed sensing control valve 15 is a rotational speed sensing control valve that can generate a control pressure P3 port proportional to the rotational speed of the gear pump 14, and the P3 oil port of the rotational speed sensing control valve 15 is connected to the control oil port of the variable throttle valve 17 to control the throttle opening of the variable throttle valve 17, thereby adjusting the oil suction flow rate of the gear pump 14.

[0050] When the pressure at the working oil port P4 of the working pump assembly 3 is lower than ΔP1, the oil outlet P5 of the gear pump 14 is connected to the rotational speed sensing control valve 15, and returns to the hydraulic oil tank 1 through the rotational speed sensing control valve 15 and the low-pressure overflow valve; at the same time, the gear pump 14 sucks oil from the hydraulic oil tank 1 through the variable throttle valve 17, and the oil suction flow rate decreases. At this time, the gear pump 14 no longer provides hydraulic fluid to the multi-way valve 4, but the gear pump 14 is in a small-flow self-lubrication state, that is, in a "standby" state to reduce system energy loss. At the same time, Figure 3 A schematic diagram of the power flow transmission route of the rotational speed sensing control valve 15 is shown, in combination with Figure 2 and Figure 3 As shown, through the rotational speed sensing control valve 15, it is possible to automatically control the throttle opening of the variable throttle valve 17 according to the change in the rotational speed of the gear pump 14, thereby matching the oil suction lubrication flow rate.

[0051] The specific working process of this embodiment is as follows:

[0052] When the steering gear 8 is not operating and the working hydraulic cylinder 5 is not operating: The oil outlet of the steering gear pump 2 enters the neutral position of the multi-way valve 4 and returns to the hydraulic oil tank 1 through the second working EF port of the priority valve 9; the pressure at the working port P4 of the working pump assembly 3 is lower than the spring force ΔP2 at the left end of the first reversing valve 18, and at the same time, the pressure at the working port P4 of the working pump assembly 3 is lower than the spring force ΔP1 at the left end of the second reversing valve 19. The gear pump 14 sucks oil from the hydraulic oil tank 1 through the variable throttle valve 17. The oil outlet P5 of the gear pump 14 returns to the hydraulic oil tank 1 through the P2 port of the rotational speed sensing control valve 15 and the low-pressure overflow valve. At this time, the gear pump 14 no longer supplies hydraulic fluid to the multi-way valve 4, and the oil suction flow rate decreases. The gear pump 14 is in a small-flow self-lubricating state, maintaining extremely low power consumption operation;

[0053] When the steering gear 8 is operating and the working hydraulic cylinder 5 is not operating: The oil outlet of the steering gear pump 2 provides hydraulic fluid for the steering gear 8 through the first working CF port of the priority valve 9, thereby driving the movement of the steering hydraulic cylinder 7 and driving the whole machine to steer. When the steering load exceeds the rated value or the stroke of the steering cylinder is at the limit position, the LS port of the priority valve 9 is depressurized, and the oil from the steering gear pump 2 enters the neutral position of the multi-way valve 4 and returns to the hydraulic oil tank 1 through the second working EF port of the priority valve 9; at the same time, the working hydraulic cylinder 5 is not operating, the pressure at the working port P4 of the working pump assembly 3 is lower than the spring force ΔP2 at the left end of the first reversing valve 18, and at the same time, the pressure at the working port P4 of the working pump assembly 3 is lower than the spring force ΔP1 at the left end of the second reversing valve 19. The gear pump 14 sucks oil from the hydraulic oil tank 1 through the variable throttle valve 17. The oil outlet P5 of the gear pump 14 returns to the hydraulic oil tank 1 through the P2 port of the rotational speed sensing control valve 15 and the low-pressure overflow valve. At this time, the gear pump 14 no longer supplies hydraulic fluid to the multi-way valve 4, and the oil suction flow rate decreases. The gear pump 14 is in a small-flow self-lubricating state, maintaining extremely low power consumption operation;

[0054] When the steering gear 8 is not operating and the working hydraulic cylinder 5 is operating: The oil outlet of the steering gear pump 2 enters the multi-way valve 4 through the second working EF port of the priority valve 9. When the working hydraulic cylinder 5 is operating, the pressure at the working port P4 of the working pump assembly 3 is higher than the spring force ΔP2 at the left end of the first reversing valve 18, and the pressure at the working port P4 of the working pump assembly 3 is higher than the spring force ΔP1 at the left end of the second reversing valve 19. The gear pump 14 sucks oil from the hydraulic oil tank 1 through the first reversing valve 18, and the outlet of the gear pump 14 enters the multi-way valve 4 through the check valve 20. At this time, the gear pump 14 sucks oil without passing through the variable throttle valve 17 and operates at full displacement. The combined oil fluid of the gear pump 14 and the steering gear pump 2 together pushes the working hydraulic cylinder 5 to operate. When the working load exceeds the rated value or the working hydraulic cylinder stroke is at the limit position, the main safety valve of the multi-way valve 9 opens, and the oil output from the gear pump 14 returns to the hydraulic oil tank 1 through the main safety valve of the multi-way valve 9. And at this time, the pressure at the inlet port of the multi-way valve 4 reaches the set pressure of the one-way unloading valve 10, and the hydraulic fluid provided by the steering gear pump 2 to the working hydraulic cylinder 5 through the EF port of the priority valve 9 is unloaded back to the hydraulic oil tank 1 through the one-way unloading valve 10, avoiding energy waste caused by high pressure in the steering hydraulic system.

[0055] When the steering gear 8 is operating and the working hydraulic cylinder 5 is operating: The oil outlet of the steering gear pump 2 provides hydraulic fluid for the steering gear 8 through the first working CF port of the priority valve 9, and then drives the steering hydraulic cylinder 7 to move to drive the whole machine to steer. When the steering load exceeds the rated value or the steering cylinder stroke is at the limit position, the LS port of the priority valve 9 is depressurized, and the oil from the steering gear pump 2 enters the multi-way valve 4 through the second working EF port of the priority valve 9; at the same time, the working hydraulic cylinder 5 is operating, the pressure at the working port P4 of the working pump assembly 3 is higher than the spring force ΔP2 at the left end of the first reversing valve 18, and the pressure at the working port P4 of the working pump assembly 3 is higher than the spring force ΔP1 at the left end of the second reversing valve 19. The gear pump 14 sucks oil from the hydraulic oil tank 1 through the first reversing valve 18, and the outlet of the gear pump 14 enters the multi-way valve 4 through the check valve 20. At this time, the gear pump 14 sucks oil without passing through the variable throttle valve 17 and operates at full displacement. The combined oil fluid of the gear pump 14 and the steering gear pump 2 together pushes the working hydraulic cylinder 5 to operate. When the working load exceeds the rated value or the working hydraulic cylinder stroke is at the limit position, the main safety valve of the multi-way valve 9 opens, and the oil output from the gear pump 14 returns to the hydraulic oil tank 1 through the high-pressure overflow of the main safety valve of the multi-way valve 9. And at this time, the pressure at the inlet port of the multi-way valve 4 reaches the set pressure of the one-way unloading valve 10, and the hydraulic fluid provided by the steering gear pump 2 to the working hydraulic cylinder 5 through the EF port of the priority valve 9 is unloaded back to the hydraulic oil tank 1 through the one-way unloading valve 10, avoiding energy waste caused by high pressure in the steering hydraulic system.

[0056] Meanwhile, when the gear pump 14 is in the small-flow self-lubrication state, that is, the oil outlet P5 of the gear pump 14 is connected to the rotational speed sensing control valve 15, and it returns to the hydraulic oil tank 1 through the P2 port of the rotational speed sensing control valve 15 and the low-pressure overflow valve; at the same time, the gear pump 14 sucks oil from the hydraulic oil tank 1 through the variable throttle valve 17, the oil suction flow rate decreases, and at this time the gear pump 14 no longer supplies hydraulic fluid to the multi-way valve 4, but is in a "standby" state to reduce the energy loss of the system.

[0057] Combined Figure 2 with Figure 3 As shown, through the rotational speed sensing control valve 15, it is possible to automatically control the opening of the throttle port of the variable throttle valve 17 according to the change in the rotational speed of the gear pump 14, and thus match the lubricating oil suction flow rate.

[0058] When the rotational speed of the gear pump 14 increases as the rotational speed of the prime mover increases, the output flow rate of the gear pump 14 increases, that is, the oil inlet flow rate Q1 of the rotational speed sensing control valve 15 increases. Through the rotational speed sensing control of the rotational speed sensing control valve 15, the control pressure P3 output by the rotational speed sensing control valve 15 increases. The control pressure P3 acts on the variable throttle valve 17 to open the throttle port, and thus synchronously increases the lubricating oil suction flow rate of the gear pump 14 to ensure that the gear pump 14 is fully lubricated and cooled during high-speed operation.

[0059] When the rotational speed of the gear pump 14 decreases as the rotational speed of the prime mover decreases, the output flow rate of the gear pump 14 decreases, that is, the oil inlet flow rate Q1 of the rotational speed sensing control valve 15 decreases. Through the rotational speed sensing control of the rotational speed sensing control valve 15, the control pressure P3 output by the rotational speed sensing control valve 15 decreases. The control pressure P3 acts on the variable throttle valve 17 to close the throttle port, and thus synchronously reduces the lubricating oil suction flow rate of the gear pump 14 to further reduce the energy consumption of the system.

[0060] Embodiment 2

[0061] This embodiment discloses a wheel loader that applies the energy-saving hydraulic system in Embodiment 1. When the wheel loader is traveling at high speed, the working hydraulic cylinder 5 does not move, and only the steering cylinder 7 needs to move. At this time, the working gear pump 14 is in the small-flow self-lubrication state and no longer supplies flow to the reversing valve 4, avoiding the energy waste caused by the large flow of the working pump returning to the oil through the neutral position of the multi-way valve. At the same time, it can also further reduce the system heat generation; when the working boom of the wheel loader is lifted to the top or the bucket is retracted to the limit position, the pressure of the working hydraulic system rises to the set pressure of the multi-way valve safety valve. By using a one-way unloading valve, while ensuring that the pressure of the working hydraulic system is maintained, the excess oil in the steering hydraulic system can be directly unloaded back to the oil tank, avoiding the energy waste caused by the high-pressure overflow of the steering hydraulic system.

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An energy-saving hydraulic system, characterized in that, It includes a hydraulic oil tank (1), a steering gear pump (2), a working pump assembly (3), a working hydraulic cylinder (5), a steering hydraulic cylinder (7) and a priority valve (9). The working pump assembly (3) includes a gear pump (14), a rotational speed sensing control valve (15), a low-pressure overflow valve (16), a variable throttle valve (17), a first reversing valve (18), a second reversing valve (19), a working oil port P4 and a suction port T2. The inlet port of the steering gear pump (2) is communicated with the hydraulic oil tank (1). The outlet port of the steering gear pump (2) is connected to the inlet port P of the priority valve (9). The first working oil port CF of the priority valve (9) supplies oil to the steering hydraulic cylinder (7), and the second working oil port EF of the priority valve (9) supplies oil to the working hydraulic cylinder (5). The suction port T2 of the working pump assembly (3) is communicated with the hydraulic oil tank (1). The working oil port P4 of the working pump assembly (3) supplies oil to the working hydraulic cylinder (5). The suction port T2 of the working pump assembly (3) is connected to the suction port T1 of the gear pump (14) through the variable throttle valve (17). The outlet port of the gear pump (14) is connected to the inlet end of the second reversing valve (19). The first outlet end of the second reversing valve (19) is connected to the Q1 oil port of the rotational speed sensing control valve (15). The second outlet end of the second reversing valve (19) is connected to the working oil port P4. The control oil port LS1 of the second reversing valve (19) is connected to the working oil port P4. The P2 oil port of the rotational speed sensing control valve (15) is communicated with the hydraulic oil tank (1) through the low-pressure overflow valve (16). The P3 oil port of the rotational speed sensing control valve (15) is communicated with the control oil port of the variable throttle valve (17). The inlet end and the outlet end of the first reversing valve (18) are respectively connected to both ends of the variable throttle valve (17). The control oil port LS2 of the first reversing valve (18) is connected to the working oil port P4.

2. An energy-saving hydraulic system according to claim 1, characterized in that, The working pump assembly (3) further includes a check valve (20). The inlet port of the check valve (20) is connected to the second outlet end of the second reversing valve (19), and the outlet port of the check valve (20) is connected to the working oil port P4.

3. An energy-saving hydraulic system according to claim 1, characterized in that, It further includes a multi-way valve (4), a pilot oil source valve (13) and a pilot valve (6). The multi-way valve (4) includes an inlet port P, a first working port, a second working port, pilot oil ports a1, b1, a2, b2 and a return port T. The inlet port P is connected to the working oil port P4 of the working pump assembly (3). The first working port and the second working port are respectively communicated with different working hydraulic cylinders (5). The return port T of the multi-way valve (4) is connected to the hydraulic oil tank (1). The inlet port P1 of the pilot oil source valve (13) is connected to the outlet port of the steering gear pump (2). The outlet port U of the pilot oil source valve (13) is connected to the inlet port P of the pilot valve (6). The return port T of the pilot oil source valve (13) is connected to the hydraulic oil tank (1). The outlet ports 1a, 1b, 2a, 2b of the pilot valve (6) are respectively connected to the corresponding pilot oil ports a1, b1, a2, b2 of the multi-way valve (4).

4. An energy-saving hydraulic system according to claim 3, characterized in that, It also includes a steering gear (8) and a one-way unloading valve (10); The first working oil port CF port of the priority valve (9) is connected to the oil inlet of the steering gear (8), the second working oil port EF port of the priority valve (9) is connected to the oil inlet of the multi-way valve (4) through the one-way unloading valve (10), and the unloading port of the one-way unloading valve (10) is communicated with the hydraulic oil tank (1); The number of the steering hydraulic cylinders (7) is two. The rodless cavity of the first steering hydraulic cylinder is communicated with the R port of the steering gear (8), the rod chamber is communicated with the L port of the steering gear (8), the rodless cavity of the second steering hydraulic cylinder is communicated with the L port of the steering gear (8), and the rod chamber is communicated with the R port of the steering gear (8).

5. An energy-saving hydraulic system according to claim 3, characterized in that, It also includes a radiator (11) and a filter (12) arranged between the return port T port of the multi-way valve (4) and the hydraulic oil tank (1).

6. An energy-saving hydraulic system according to claim 1, characterized in that, The hydraulic oil tank (1) is a pre-pressurized hydraulic oil tank with an exhaust pre-pressurized air filter.

7. An energy-saving hydraulic system according to claim 3, characterized in that, The multi-way valve (4) is a pilot control open center multi-way valve.

8. An energy-saving hydraulic system according to claim 3, characterized in that, The pilot valve (6) is a hydraulically controlled pilot valve.

9. An energy-saving hydraulic system according to claim 4, characterized in that, The steering gear (8) is a load sensing full hydraulic steering gear.

10. A loader, characterized in that, Apply the energy-saving hydraulic system according to any one of claims 1-9.

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