Hydraulic systems and construction vehicles

Abstract

The present invention relates to a hydraulic system and an engineering vehicle, wherein the hydraulic system comprises: a working hydraulic cylinder (16) for driving a working component to move; a working hydraulic pump, comprising a first hydraulic pump (7) for providing hydraulic fluid to the working hydraulic cylinder (16) and a second hydraulic pump (8) for providing hydraulic fluid to the working hydraulic cylinder (16); and an unloading valve (9) connected to the second hydraulic pump (8) for discharging the hydraulic fluid discharged by the second hydraulic pump (8) to a hydraulic fluid box (1) when the load pressure of the working hydraulic cylinder (16) is greater than a predetermined value. The technical solution of the present invention is applied to improve the problems of low working efficiency and high energy consumption of engineering vehicles existing in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering equipment, and in particular to a hydraulic system and an engineering vehicle. Background Art

[0002] In the prior art, the hydraulic systems of engineering vehicles such as loaders are mostly fixed-flow systems with overflow losses. The fixed-variable hydraulic systems that emerged later are basically steering and working combined systems with a more complex structure. When the working system is working, the variable pump becomes a fixed-flow pump, and the system pipeline losses are large, resulting in higher fuel losses.

[0003] The hydraulic system of engineering vehicles is generally slow to respond in low temperature environments due to its cumbersome variable signal control. The lower the hydraulic oil temperature, the slower the system response. Therefore, it is not suitable for certain working conditions of the loader, affecting the efficiency of the loader. Summary of the invention

[0004] The present invention aims to provide a hydraulic system and an engineering vehicle, so as to improve the problem of high energy consumption of the engineering vehicle existing in the prior art.

[0005] According to one aspect of an embodiment of the present invention, the present invention provides a hydraulic system, the hydraulic system comprising:

[0006] Working hydraulic cylinder, used to drive the working parts to move;

[0007] A working hydraulic pump, comprising a first hydraulic pump for supplying hydraulic fluid to the working hydraulic cylinder and a second hydraulic pump for supplying hydraulic fluid to the working hydraulic cylinder;

[0008] The unloading valve is communicated with the second hydraulic pump and is used for discharging the hydraulic fluid discharged from the second hydraulic pump to the hydraulic fluid tank when the load pressure of the working hydraulic cylinder is greater than a predetermined value.

[0009] Optionally, the unloading valve comprises a buffer valve, and the buffer valve comprises:

[0010] Valve body;

[0011] a first inlet, provided on the valve body and connected to the second hydraulic pump;

[0012] A first outlet, provided on the valve body and used for communicating with the hydraulic fluid tank;

[0013] The valve core is movably arranged in the valve body and has a first position and a second position. In the first position, the first inlet and the first outlet are connected. In the second position, the passage between the first inlet and the first outlet is cut off.

[0014] Optionally, the valve core also has a third position, which is located between the first position and the second position along the moving direction of the valve core. When the valve core is in the third position, the flow area of ​​the channel between the first inlet and the first outlet is smaller than when the valve core is in the first position.

[0015] Optionally, the buffer valve further comprises:

[0016] A control fluid inlet for introducing hydraulic fluid that feeds back the load pressure of the working hydraulic cylinder to push the valve core from the second position to the first position;

[0017] The control fluid outlet discharges the hydraulic fluid when the valve core moves from the second position to the first position.

[0018] a second inlet, communicating with the control fluid outlet;

[0019] The second outlet is used to communicate with the hydraulic fluid tank. When the valve core is in the first position, the passage between the second inlet and the second outlet is cut off. When the valve core is in the second position, the second inlet is communicated with the second outlet.

[0020] Optionally, the valve core also has a third position, which is located between the first position and the second position along the moving direction of the valve core. When the valve core is in the third position, the flow area of ​​the channel between the first inlet and the first outlet is smaller than when the valve core is in the first position, and the second inlet and the second outlet are connected.

[0021] Optionally, the unloading valve further comprises:

[0022] The second relief valve includes an inlet communicating with the pipeline between the second hydraulic pump and the working hydraulic cylinder and an outlet communicating with the control fluid inlet of the buffer valve.

[0023] Optionally, the unloading valve further comprises a control fluid flow path, the control fluid flow path comprises an inlet end connected to the control fluid inlet of the reversing valve and an outlet end for connecting to the hydraulic fluid tank, and a first throttling component is provided in the control fluid flow path.

[0024] Optionally, the unloading valve further comprises a one-way valve, an inlet of which is connected to the second hydraulic pump, and the one-way valve is located on the flow path between the working hydraulic cylinders of the second hydraulic pump and upstream of the second overflow valve.

[0025] Optionally, the unloading valve further comprises:

[0026] a first flow path, communicating with the control fluid outlet and the second inlet;

[0027] a second flow path communicating with the control fluid outlet and the hydraulic fluid tank; and

[0028] The second throttling component is arranged in the second flow path and is used for throttling the hydraulic fluid flowing from the control fluid outlet to the hydraulic fluid tank.

[0029] Optionally, the second throttling component includes a one-way throttle valve, and the one-way throttle valve includes a one-way valve and a throttling component connected in parallel with the one-way valve.

[0030] According to another aspect of the present invention, there is provided an engineering machine, which comprises the above-mentioned hydraulic system.

[0031] Optionally, the construction machinery includes a loader.

[0032] By applying the technical solution of the present application, when the load pressure of the working hydraulic cylinder is greater than a predetermined value, the hydraulic fluid discharged by the second hydraulic pump is no longer delivered to the working hydraulic cylinder, but directly flows back to the hydraulic fluid tank. The hydraulic system can avoid that both the first hydraulic pump and the second hydraulic pump work in a high-power working state, which is beneficial to reducing the energy consumption of the hydraulic system.

[0033] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 A schematic structural diagram of a hydraulic system according to an embodiment of the present invention is shown;

[0036] Figure 2 A schematic diagram showing the structure of a unloading valve of a hydraulic system according to an embodiment of the present invention; and

[0037] Figure 3 The pressure variation curve of the working hydraulic cylinder of the hydraulic system with unoptimized unloading valve during the unloading process is shown;

[0038] Figure 4 The figure shows the pressure variation curve of the working hydraulic cylinder of the hydraulic system of the embodiment of the present invention during the unloading process. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Figure 1 The structural diagram of the hydraulic system of this embodiment is shown in FIG. Figure 1 As shown, the hydraulic system of this embodiment includes a steering hydraulic cylinder 5 for driving the steering of the wheels, a variable displacement pump 2 for providing hydraulic fluid to the steering hydraulic cylinder 5 , and a steering valve 4 for controlling the movement of the steering hydraulic cylinder 5 .

[0041] The steering valve 4 has a first state in which the piston rod of the steering hydraulic cylinder 5 is extended, and a second state in which the piston rod of the steering hydraulic cylinder 5 is retracted.

[0042] The hydraulic system also includes a steering gear 3 for controlling the switching state of the steering valve 4 and a pilot oil source valve 12 for providing hydraulic fluid to the steering gear 3. The pilot oil source valve 12 includes an inlet P1 connected to the variable pump 2, a first working port A for outputting the pilot hydraulic fluid, and a second working port B for outputting the pilot hydraulic fluid. Among them, the second working port B of the pilot oil source valve 12 is used to provide hydraulic fluid to the steering gear 3. The pilot oil source valve 12 is integrated on the variable pump 2 and can receive the hydraulic fluid provided by the hydraulic variable pump 2 at the closest distance.

[0043] The hydraulic system also includes another steering hydraulic cylinder, whose rodless chamber is connected to the second working port of the reversing valve 41, and whose rod chamber is connected to the first working port of the reversing valve 41. Therefore, when the piston rods of the two steering hydraulic cylinders are extended, the piston rod of the other steering hydraulic cylinder is retracted, and the two steering hydraulic cylinders cooperate to drive the wheel steering.

[0044] The hydraulic system further comprises a working hydraulic cylinder 16, which is used to drive the working component to move. The working component may be one of a bucket of a loader, a boom of a crane, and an excavating arm of an excavator.

[0045] The hydraulic system further includes a working hydraulic pump for providing hydraulic fluid to the working hydraulic cylinder 16 . The working hydraulic pump includes a first hydraulic pump 7 and a second hydraulic pump 8 . Both the first hydraulic pump 7 and the second hydraulic pump 8 can independently provide hydraulic fluid to the working hydraulic cylinder 16 .

[0046] Optionally, the working hydraulic pump is a double gear pump, the first hydraulic pump 7 is a first gear pump of the double gear pump, and the second hydraulic pump 8 is a second gear pump of the double gear pump.

[0047] The hydraulic system also includes a working hydraulic cylinder reversing valve 15 for controlling the movement direction of the working hydraulic cylinder 16. The working hydraulic cylinder reversing valve 15 includes an inlet P connected to both the first hydraulic pump 7 and the second hydraulic pump 8, a return port T connected to the hydraulic fluid tank 1, a first working port connected to the rod chamber of the working hydraulic cylinder 16, and a second working port connected to the rodless chamber of the working hydraulic cylinder 16.

[0048] The hydraulic system further includes a radiator 10 and a filter 11 which are arranged in a pipeline between a return port T of the working hydraulic cylinder reversing valve 15 and the hydraulic fluid tank 1 .

[0049] The working hydraulic cylinder reversing valve 15 has a first working state and a second working state. In the first working state, the inlet P of the working hydraulic cylinder reversing valve 15 is connected to the first working port and the return port T is connected to the second working port. In the second working state, the inlet P of the working hydraulic cylinder reversing valve 15 is connected to the second working port and the return port T is connected to the first working port. The working hydraulic cylinder reversing valve 15 can be hydraulic pilot controlled and electric proportional pilot controlled.

[0050] The hydraulic system also includes a pilot valve 14 for controlling the working hydraulic cylinder reversing valve 15 to switch the working state. The pilot valve 14 includes an inlet P connected to the first working port A of the pilot oil source valve 12, a return port T connected to the hydraulic fluid tank 1, and an outlet connected to the control fluid port of the working hydraulic cylinder reversing valve 15.

[0051] The pilot valve 14 can be a manual pilot valve or an electromagnetic pilot valve. The user controls the working component to operate by manipulating the pilot valve 14.

[0052] The hydraulic system further includes a stop valve 13 provided on the flow path between the pilot valve 14 and the first working port A of the pilot oil source valve 12 .

[0053] The hydraulic system also includes a unloading valve 9 connected to the second hydraulic pump 8. The unloading valve 9 is used to discharge the hydraulic fluid discharged from the second hydraulic cylinder 8 to the hydraulic fluid tank 1 when the load pressure of the working hydraulic cylinder 16 is greater than a predetermined value. When the load pressure of the working hydraulic cylinder 16 is greater than a predetermined value, the hydraulic fluid discharged from the second hydraulic pump 8 is no longer transported to the working hydraulic cylinder 16, but directly flows back to the hydraulic fluid tank 1. The hydraulic system can avoid that the first hydraulic pump 7 and the second hydraulic pump 8 both work in a high-power working state, which is beneficial to reducing the energy consumption of the hydraulic system.

[0054] Figure 2 An enlarged view of the unloading valve 9 of the hydraulic system of this embodiment is shown, combined with Figure 1 and Figure 2 As shown, the unloading valve 9 of this embodiment includes an inlet P communicated with the second hydraulic pump 8 and an outlet A communicated with the inlet P of the working hydraulic cylinder reversing valve 15 .

[0055] The unloading valve 9 includes a buffer valve 22, which includes a valve body, a first inlet arranged on the valve body, a first outlet arranged on the valve body and a valve core movably arranged in the valve body, and the valve core has a first position and a second position. In the first position, the first inlet and the first outlet are connected, and in the second position, the channel between the first inlet and the first outlet is cut off.

[0056] The unloading valve 9 further includes a second relief valve 21, which includes an inlet connected to the pipeline between the second hydraulic pump 8 and the working hydraulic cylinder 16 and an outlet connected to the control fluid inlet of the buffer valve 22. The second relief valve 21 is used to deliver hydraulic fluid to the buffer valve 22 to push the valve core of the buffer valve 22 from the second position to the first position.

[0057] The unloading valve 9 further includes a one-way valve 20 , which is located on the flow path between the working hydraulic cylinders 16 of the second hydraulic pump 8 and upstream of the second overflow valve 21 .

[0058] When the load pressure of the working hydraulic cylinder 16 increases, the pressure of the hydraulic fluid in the flow path between the inlet of the working hydraulic cylinder reversing valve 15 and the second hydraulic pump 8 also increases. When the load pressure of the working hydraulic cylinder 16 is greater than a predetermined value, the hydraulic fluid discharged by the second overflow valve 21 pushes the valve core of the buffer valve 22 from the second position to the first position, so that the hydraulic fluid discharged by the second hydraulic pump 8 directly flows back to the hydraulic fluid tank 1, thereby avoiding the first hydraulic pump 7 and the second hydraulic pump 8 both working under high-power conditions, which is beneficial to reducing the energy consumption of the hydraulic system.

[0059] The valve core also has a third position, which is located between the first position and the second position along the moving direction of the valve core. When the valve core is in the third position, the flow area of ​​the channel between the first inlet and the first outlet is smaller than when the valve core is in the first position. Figure 2 As shown, when the buffer valve 22 is opened due to excessive load pressure of the working hydraulic cylinder 16, the valve core of the buffer valve 22 moves from the second position to the first position via the third position. Figure 2 The lower valve position of the middle buffer valve 22 corresponds to the second position of the valve core. Figure 2 The middle valve position of the middle buffer valve 22 corresponds to the third position of the valve core. Figure 2 The upper valve position of the buffer valve corresponds to the first position of the valve core.

[0060] It can be seen that when the buffer valve of the unloading valve 9 is opened, the flow area of ​​the channel between the second hydraulic pump 8 and the hydraulic fluid box 1 gradually increases, which is beneficial to reducing the impact and noise of the hydraulic system.

[0061] The buffer valve 22 also includes a control fluid inlet for introducing hydraulic fluid for feeding back the load pressure of the working hydraulic cylinder 16, a control fluid outlet for discharging the hydraulic fluid when the valve core moves from the second position to the first position, a second inlet connected to the control fluid outlet, and a second outlet for connecting to the hydraulic fluid tank 1, and when the valve core is in the second position, the second inlet is connected to the second outlet.

[0062] The unloading valve 9 further includes a control fluid flow path, which includes an inlet end communicating with the control fluid inlet of the reversing valve 22 and an outlet end for communicating with the hydraulic fluid tank 1, and a first throttling component 23 is provided in the control fluid flow path. When the valve core of the buffer valve 22 moves from the first position to the second position, the hydraulic fluid discharged from the control fluid inlet of the buffer valve flows to the hydraulic fluid tank 1 through the control fluid flow path.

[0063] The unloading valve 9 also includes a first flow path 26 for connecting the control fluid outlet and the second inlet, a second flow path 25 for connecting the control fluid port and the hydraulic fluid tank 1, and a second throttling component 24 arranged in the second flow path, and the second throttling component 24 is used to throttle the hydraulic fluid flowing from the control fluid outlet to the hydraulic fluid tank 1.

[0064] When the valve core is in the third position, the second inlet is connected to the second outlet. It can be seen that in the process of the valve core moving from the second position to the first position, when the valve core is in the second position and the third position, the hydraulic fluid discharged from the control fluid outlet flows to the hydraulic fluid tank 1 through the first flow path 26, the second inlet and the second outlet.

[0065] After the valve core reaches the first position, it can continue to move to increase the opening of the buffer valve 22. Figure 2 The upper valve position of the buffer valve 22 shown in the figure, when the valve core continues to move after reaching the first position to increase the opening of the buffer valve 22, the hydraulic fluid discharged from the control fluid outlet flows into the hydraulic fluid tank 1 through the second flow path 25.

[0066] Figure 3 The pressure variation curve of the working hydraulic cylinder of the hydraulic system with unoptimized unloading valve during the unloading process is shown. The pressure fluctuation of the curve is large and the pressure peak is high, which affects the reliability of the hydraulic components and the system.

[0067] Figure 4 The pressure variation curves of the first hydraulic pump 7 and the second hydraulic pump 8 during the unloading process of the hydraulic system are shown. The pressure is stable during the unloading process, and the pressure peak is low, which improves the life of the hydraulic system.

[0068] In this embodiment, the variable displacement pump 2 only provides hydraulic fluid to the steering hydraulic cylinder 5 , and the working hydraulic pump only provides hydraulic fluid to the working hydraulic cylinder 16 .

[0069] The working hydraulic pump is a hydraulic double gear pump. The first double gear pump (first hydraulic pump 7) directly provides hydraulic fluid to the working hydraulic cylinder reversing valve 15, and the second double gear pump (second hydraulic pump 8) provides hydraulic fluid to the working hydraulic cylinder reversing valve 15 through the unloading valve 9. During the operation of the system, the pressure at the output port of the unloading valve 9 increases, that is, the pressure after the one-way valve 20 increases. When the pressure reaches the set pressure of the second overflow valve 21, the second overflow valve 21 opens, and the hydraulic fluid output by the second overflow valve 21 pushes the buffer valve 22 to open. At the same time, the control fluid outlet of the buffer valve 22 discharges the hydraulic fluid. When the valve core of the buffer valve 22 moves, the hydraulic fluid output from the control fluid outlet flows to the hydraulic fluid tank 1 through the first flow path 26 and the second flow path 25, so the buffer valve 22 can be opened quickly. Afterwards, as the valve core of the buffer valve 22 moves, the channel between the second outlet and the second inlet is cut off, and the hydraulic fluid discharged from the control fluid outlet of the buffer valve 22 can only flow to the hydraulic fluid tank 1 through the second flow path 25, which slows down the movement speed of the valve core of the buffer valve, so that the valve core of the buffer valve 22 moves slowly to slowly increase the opening of the buffer valve 22 to the maximum opening. In this way, the rapid opening of the buffer valve 22 avoids high pressure shock caused by untimely unloading of the second gear pump, and at the same time unloads step by step to avoid noise caused by unloading.

[0070] When the machine is steering, the hydraulic variable pump 2 supplies hydraulic fluid to the steering hydraulic cylinder on demand. When the working parts of the engineering vehicle are operating, the working hydraulic pump provides hydraulic fluid to the working hydraulic cylinder 16. The steering system and the working system are independent of each other, avoiding mutual interference and improving the reliability and work efficiency of the steering and working systems.

[0071] According to another aspect of the present invention, this embodiment further provides an engineering vehicle, which includes the above-mentioned hydraulic system.

[0072] The above description is only an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A hydraulic system, characterized in that: include: A working hydraulic cylinder (16), used for driving the working parts to move; A working hydraulic pump, comprising a first hydraulic pump (7) for supplying hydraulic fluid to the working hydraulic cylinder (16) and a second hydraulic pump (8) for supplying hydraulic fluid to the working hydraulic cylinder (16); an unloading valve (9) connected to the second hydraulic pump (8) and used for discharging the hydraulic fluid discharged by the second hydraulic pump (8) to the hydraulic fluid tank (1) when the load pressure of the working hydraulic cylinder (16) is greater than a predetermined value, The unloading valve (9) comprises a buffer valve (22), and the buffer valve (22) comprises: Valve body; a first inlet, provided on the valve body and connected to the second hydraulic pump (8); a first outlet, provided on the valve body and used for communicating with a hydraulic fluid tank (1); The valve core is movably disposed in the valve body and has a first position and a second position. In the first position, the first inlet and the first outlet are connected. In the second position, the passage between the first inlet and the first outlet is cut off. A control fluid inlet for introducing hydraulic fluid that feeds back the load pressure of the working hydraulic cylinder (16) to push the valve core from the second position to the first position; a control fluid outlet for discharging hydraulic fluid when the valve core moves from the second position to the first position, and a second inlet for communicating with the control fluid outlet; The second outlet is used to communicate with the hydraulic fluid tank (1); when the valve core is in the first position, the passage between the second inlet and the second outlet is cut off; when the valve core is in the second position, the second inlet is communicated with the second outlet.

2. The hydraulic system according to claim 1, characterized in that: The valve core also has a third position, which is located between the first position and the second position along the moving direction of the valve core. When the valve core is in the third position, the flow area of ​​the channel between the first inlet and the first outlet is smaller than when the valve core is in the first position.

3. The hydraulic system according to claim 1, characterized in that: The valve core also has a third position, which is located between the first position and the second position along the moving direction of the valve core. When the valve core is in the third position, the flow area of ​​the channel between the first inlet and the first outlet is smaller than when the valve core is in the first position, and the second inlet and the second outlet are connected.

4. The hydraulic system according to claim 1, characterized in that: The unloading valve (9) further comprises: a second relief valve (21) comprising an inlet connected to a pipeline between the second hydraulic pump (8) and the working hydraulic cylinder (16) and an outlet connected to a control fluid inlet of the buffer valve (22); A control fluid flow path, comprising an inlet end connected to a control fluid inlet of a buffer valve (22) and an outlet end for connecting to a hydraulic fluid tank (1), wherein a first throttling component (23) is provided in the control fluid flow path; A one-way valve (20), the inlet of which is connected to the second hydraulic pump (8), the one-way valve (20) being located on the flow path between the working hydraulic cylinders (16) of the second hydraulic pump (8) and being located upstream of the second overflow valve (21).

5. The hydraulic system according to claim 1, characterized in that: The unloading valve (9) further comprises: a first flow path (26) communicating the control fluid outlet and the second inlet; A second flow path (25) connects the control fluid outlet and the hydraulic fluid box (1); and a second throttling component (24) is arranged in the second flow path (25) for throttling the hydraulic fluid flowing from the control fluid outlet to the hydraulic fluid box (1).

6. The hydraulic system according to claim 5, characterized in that: The second throttle component (24) comprises a one-way throttle valve, which comprises a one-way valve and a throttle component connected in parallel with the one-way valve.

7. An engineering machine, characterized in that: A hydraulic system comprising any one of claims 1 to 5.

8. The construction machine according to claim 7, characterized in that: Including loader.

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