A walking hydraulic system and an engineering vehicle thereof

Abstract

This application provides a hydraulic system for travel and an engineering vehicle thereof, belonging to the field of engineering machinery technology. The pressure control valve of the hydraulic system switches between a first opening state and a second opening state according to the vehicle's braking stroke. In the first opening state, the pressure oil in the first accumulator is output as high-pressure control oil via the pressure control valve and flows into the control chamber of the hydraulic directional valve. In the second opening state, the pressure oil in the first accumulator is output as low-pressure control oil via the pressure control valve and flows into the control chamber of the hydraulic directional valve. The hydraulic directional valve is used to be partially open under the actuation of low-pressure control oil and open under the actuation of high-pressure control oil to regulate the flow rate of hydraulic oil from the hydraulic travel assembly to the first accumulator via the hydraulic directional valve. This allows energy recovery to adapt to and match the vehicle's braking stroke, resulting in good energy recovery without affecting the vehicle's braking performance.

Description

Technical Field

[0001] This application relates to the field of engineering machinery technology, and in particular to a walking hydraulic system and its engineering vehicle. Background Technology

[0002] Since vehicles such as excavators and loaders frequently decelerate and brake during operation, and consume a lot of energy during operation, recycling and reusing braking energy can reduce exhaust emissions and fuel consumption, thus achieving the goal of energy conservation and emission reduction.

[0003] In related technologies, an energy recovery system for construction machinery includes a hydraulic pump and a hydraulic motor. The hydraulic pump drives the hydraulic motor, and the hydraulic pump and the hydraulic motor form a closed loop and together constitute part of a closed system. The energy recovery system includes an accumulator. When the construction machinery brakes, the energy recovery system can store a portion of the hydraulic fluid on the high-pressure side of the closed system into the accumulator to recover braking energy.

[0004] However, in some application scenarios, when the above method is used to recover braking energy, the recovery effect is poor and it will affect the vehicle's braking performance. Summary of the Invention

[0005] This application provides a walking hydraulic system and its engineering vehicle to solve the problem that the braking energy recovery method in the related technology has poor recovery effect and affects the braking effect of the vehicle.

[0006] On one hand, this application provides a walking hydraulic system, including a hydraulic walking component, an energy storage component, and a control device; the energy storage component includes at least one first accumulator, and the control device includes a pressure control valve and a hydraulic directional valve; the first accumulator is connected to the hydraulic walking component via the hydraulic directional valve, the pressure control valve is connected to the first accumulator, and the hydraulic directional valve is connected to the pressure control valve; the pressure control valve is used to switch between a first opening state and a second opening state according to the vehicle's braking stroke, wherein, in the first opening state, the pressure oil stored in the first accumulator is output as low-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve, and in the second opening state, the pressure oil stored in the first accumulator is output as high-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve; the hydraulic directional valve is used to be in a partially open state under the actuation of low-pressure control oil, and in a fully open state under the actuation of high-pressure control oil, to regulate the flow rate of hydraulic oil from the hydraulic walking component to the first accumulator through the hydraulic directional valve.

[0007] In one possible implementation, the hydraulic system for walking provided in this application further includes at least one second accumulator in the energy storage component, and the control device further includes a control element and an electromagnetic directional valve. The control element is communicatively connected to the engine of the hydraulic walking component and is used to detect the engine speed. The second accumulator is connected to the hydraulic walking component through the electromagnetic directional valve. The control element is configured to control the electromagnetic directional valve to open when the engine speed changes from a first speed to a second speed, so as to connect the hydraulic walking component and the second accumulator, allowing the hydraulic oil of the hydraulic walking component to flow into the second accumulator through the electromagnetic directional valve. The first speed is greater than the second speed.

[0008] In one possible implementation, the walking hydraulic system provided in this application further includes a brake, which is connected to the outlet of a pressure control valve, and the outlet of at least one of the first accumulator and the second accumulator is connected to the inlet of the pressure control valve. The pressure control valve is further configured to, in a first open state, output low-pressure control oil from the pressure oil in the first accumulator and / or the pressure oil in the second accumulator via the pressure control valve to the brake; and in a second open state, output high-pressure control oil from the pressure oil in the first accumulator and / or the pressure oil in the second accumulator via the pressure control valve to the brake. The brake is configured to apply a first braking force to the brake disc of the hydraulic walking assembly under the actuation of the high-pressure control oil, and to apply a second braking force to the brake disc of the hydraulic walking assembly under the actuation of the low-pressure control oil; wherein the first braking force is greater than the second braking force.

[0009] In one possible implementation, the walking hydraulic system provided in this application further includes an electro-proportional directional valve and a selector valve in the control device. The electro-proportional directional valve is electrically connected to the control unit. The outlets of the first accumulator and the second accumulator are both connected to the inlet of the electro-proportional directional valve. The outlet of the electro-proportional directional valve is connected to the high-pressure side of the hydraulic walking assembly through the selector valve. The control unit is configured to, when the engine speed changes from a third speed to a fourth speed, control the electro-proportional directional valve to open, thereby connecting the first accumulator and the high-pressure side of the hydraulic walking assembly, so that the hydraulic oil of the first accumulator flows to the high-pressure side of the hydraulic walking assembly via the electro-proportional directional valve; and to connect the second accumulator and the high-pressure side of the hydraulic walking assembly, so that the hydraulic oil of the second accumulator flows to the high-pressure side of the hydraulic walking assembly via the electro-proportional directional valve; wherein the third speed is less than the fourth speed.

[0010] In one possible implementation, the walking hydraulic system provided in this application further includes a control component configured to, when the difference between the fourth speed and the third speed is detected to be greater than a preset value, send a first command to the electro-proportional directional valve to increase the valve core opening of the electro-proportional directional valve; and, when the difference between the fourth speed and the third speed is detected to be less than or equal to a preset value, send a second command to the electro-proportional directional valve to decrease the valve core opening of the electro-proportional directional valve.

[0011] In one possible implementation, the walking hydraulic system provided in this application includes a selection valve comprising a first sub-outlet, a second sub-outlet, and an inlet. The inlet is connected to the outlet of an electro-proportional directional valve. The first sub-outlet is connected to a first side of the hydraulic walking assembly, and the second sub-outlet is connected to a second side of the hydraulic walking assembly. The selection valve is configured to connect the inlet and the first sub-outlet when the pressure on the first side is greater than the pressure on the second side; or, to connect the inlet and the second sub-outlet when the pressure on the second side is greater than the pressure on the first side.

[0012] In one possible implementation, the walking hydraulic system provided in this application further includes a first check valve and a second check valve. The first check valve is located between the hydraulically controlled directional valve and the first accumulator, and the outlet of the hydraulically controlled directional valve is connected to the inlet of the first accumulator through the first check valve. The second check valve is located between the electromagnetic directional valve and the second accumulator, and the outlet of the electromagnetic directional valve is connected to the inlet of the second accumulator through the second check valve.

[0013] In one possible implementation, the walking hydraulic system provided in this application further includes a third check valve and a fourth check valve, wherein the outlets of the first accumulator and the second accumulator are both connected to the inlet of the pressure control valve; the outlet of the first accumulator is connected to the inlet of the pressure control valve through the third check valve, and the outlet of the second accumulator is connected to the inlet of the pressure control valve through the fourth check valve.

[0014] In one possible implementation, the walking hydraulic system provided in this application further includes a pressure shut-off valve assembly, which includes a first pressure shut-off valve and a second pressure shut-off valve; the first pressure shut-off valve is located between a first check valve and a first accumulator, the outlet of the first check valve is connected to the inlet of the first pressure shut-off valve, and the outlet of the first pressure shut-off valve is connected to the inlet of the first accumulator; the second pressure shut-off valve is located between a second check valve and a second accumulator, the outlet of the second check valve is connected to the inlet of the second pressure shut-off valve, and the outlet of the second pressure shut-off valve is connected to the inlet of the second accumulator.

[0015] On the other hand, this application provides an engineering vehicle, including a vehicle body and a walking hydraulic system, as described above, disposed on the vehicle body.

[0016] The travel hydraulic system and its engineering vehicle provided in this application include a travel hydraulic system with a hydraulically controlled directional valve and at least one first accumulator. The first accumulator is connected to the hydraulic travel assembly via the hydraulically controlled directional valve to establish an energy recovery path during vehicle braking. A pressure control valve is connected to the first accumulator, and the hydraulically controlled directional valve is connected to the pressure control valve. Thus, the pressure control valve switches between a first opening state and a second opening state according to the vehicle's braking stroke, so as to provide different directional control pressures to the hydraulically controlled directional valve through the pressure oil in the first accumulator, thereby achieving proportional adjustment of the valve core position of the hydraulically controlled directional valve.

[0017] In the first opening state, corresponding to the vehicle's slow, light braking stroke, the pressure oil stored in the first accumulator is output as low-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve. This causes the hydraulic directional valve to be partially open under the push of the low-pressure control oil, thereby preventing the first accumulator from recovering a large flow of hydraulic oil from the hydraulic travel assembly through the hydraulic directional valve, which would reduce the effective flow of the hydraulic travel assembly and cause the vehicle to brake suddenly. In the second opening state, corresponding to the vehicle's emergency braking stroke, the pressure oil stored in the first accumulator is output as high-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve. This causes the hydraulic directional valve to be fully open under the push of the high-pressure control oil, thereby preventing the first accumulator from recovering a small flow of hydraulic oil from the hydraulic travel assembly through the hydraulic directional valve, which would waste energy. The travel hydraulic system provided in this application allows the energy recovery of the hydraulic travel assembly by the first accumulator through the hydraulic directional valve to adapt to and match the vehicle's braking stroke. The energy recovery effect is good, and the vehicle's braking effect is not affected while recovering energy. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] Figure 1 A schematic diagram of the walking hydraulic system provided in the embodiments of this application. Figure 1 ;

[0020] Figure 2 A schematic diagram of the walking hydraulic system provided in the embodiments of this application. Figure 2 ;

[0021] Figure 3 A schematic diagram of the walking hydraulic system provided in the embodiments of this application. Figure 3 ;

[0022] Figure 4 A schematic diagram of the walking hydraulic system provided in the embodiments of this application. Figure 4 .

[0023] Explanation of reference numerals in the attached figures:

[0024] 100-Energy Storage Component;

[0025] 110 - First accumulator; 120 - Second accumulator;

[0026] 200 - Control device;

[0027] 210 - Pressure control valve; 220 - Hydraulic directional valve; 230 - Control unit; 240 - Solenoid directional valve; 250 - Electro-proportional directional valve; 260 - Selector valve; 270 - Hydraulic oil tank;

[0028] 300 - Braking components;

[0029] 400 - First check valve; 500 - Second check valve; 600 - Third check valve; 700 - Fourth check valve;

[0030] 800 - Pressure shut-off valve assembly;

[0031] 810 - First pressure shut-off valve; 820 - Second pressure shut-off valve;

[0032] 900-Hydraulic walking assembly;

[0033] 910 - Hydraulic motor; 920 - Hydraulic pump; 930 - Engine; 940 - Shuttle valve. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0035] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those illustrated or described herein.

[0038] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0039] As stated in the background art, in the related art, there is an energy recovery system for construction machinery, the construction machinery including a hydraulic pump and a hydraulic motor, the hydraulic pump being used to drive the hydraulic motor, the hydraulic pump and the hydraulic motor forming a closed loop and together constituting part of a closed system, the energy recovery system including an accumulator, wherein, when the construction machinery brakes, the energy recovery system is able to store a portion of the hydraulic fluid on the high-pressure side of the closed system into the accumulator to realize the recovery of braking energy.

[0040] However, in some application scenarios, such as when a vehicle is slowly and lightly braking, if the flow rate of hydraulic fluid stored in the accumulator on the high-pressure side of the closed system is large, it will cause a sudden decrease in the effective flow rate of the closed system, resulting in emergency braking. Conversely, if the flow rate of hydraulic fluid stored in the accumulator on the high-pressure side of the closed system is small during emergency braking, a large amount of high-pressure hydraulic energy will be lost due to overflow. Furthermore, the braking system loses a significant amount of vehicle kinetic energy through brake pad friction, while also causing excessive wear on the brake pads, resulting in a great waste of energy. Therefore, when using the above methods to recover braking energy, the recovery effect is poor and it will affect the vehicle's braking performance.

[0041] In view of this, this application provides a walking hydraulic system and its engineering vehicle. The walking hydraulic system is provided with a hydraulically controlled directional valve and at least one first accumulator. The first accumulator is connected to the hydraulic walking assembly through the hydraulically controlled directional valve to establish an energy recovery path during vehicle braking. By providing a pressure control valve and connecting it to the first accumulator, and by connecting the hydraulically controlled directional valve to the pressure control valve, the pressure control valve switches between a first opening state and a second opening state according to the vehicle's braking stroke, so as to provide different switching control pressures to the hydraulically controlled directional valve through the pressure oil in the first accumulator, thereby realizing proportional adjustment of the valve core position of the hydraulically controlled directional valve.

[0042] In the first opening state, corresponding to the vehicle's slow, light braking stroke, the pressure oil stored in the first accumulator is output as low-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve. This causes the hydraulic directional valve to be partially open under the push of the low-pressure control oil, thereby preventing the first accumulator from recovering a large flow of hydraulic oil from the hydraulic travel assembly through the hydraulic directional valve, which would reduce the effective flow of the hydraulic travel assembly and cause the vehicle to brake suddenly. In the second opening state, corresponding to the vehicle's emergency braking stroke, the pressure oil stored in the first accumulator is output as high-pressure control oil through the pressure control valve and flows into the control chamber of the hydraulic directional valve. This causes the hydraulic directional valve to be fully open under the push of the high-pressure control oil, thereby preventing the first accumulator from recovering a small flow of hydraulic oil from the hydraulic travel assembly through the hydraulic directional valve, which would waste energy. The travel hydraulic system provided in this application allows the energy recovery of the hydraulic travel assembly by the first accumulator through the hydraulic directional valve to adapt to and match the vehicle's braking stroke. The energy recovery effect is good, and the vehicle's braking effect is not affected while recovering energy.

[0043] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0044] See Figure 1 and Figure 4 The walking hydraulic system provided in this application embodiment includes a hydraulic walking component 900, an energy storage component 100, and a control device 200; the energy storage component 100 includes at least one first energy storage device 110, and the control device 200 includes a pressure control valve 210 and a hydraulic directional valve 220; the first energy storage device 110 is connected to the hydraulic walking component 900 through the hydraulic directional valve 220, the pressure control valve 210 is connected to the first energy storage device 110, and the hydraulic directional valve 220 is connected to the pressure control valve 210.

[0045] The pressure control valve 210 is used to switch between a first opening state and a second opening state according to the vehicle's braking stroke. In the first opening state, the pressure oil stored in the first accumulator 110 is output as low-pressure control oil through the pressure control valve 210 and flows into the control chamber of the hydraulic directional valve 220. In the second opening state, the pressure oil stored in the first accumulator 110 is output as high-pressure control oil through the pressure control valve 210 and flows into the control chamber of the hydraulic directional valve 220. The hydraulic directional valve 220 is used to be partially open under the actuation of low-pressure control oil and fully open under the actuation of high-pressure control oil to regulate the flow rate of hydraulic oil from the hydraulic travel assembly 900 to the first accumulator 110 through the hydraulic directional valve 220.

[0046] It should be noted that the vehicle in this embodiment can be construction machinery, such as a snow blower, excavator, loader, etc. The hydraulic travel assembly 900 may include a hydraulic motor 910, which drives the vehicle's travel transmission system to enable the vehicle to move.

[0047] It is understood that when the walking hydraulic system of this application recovers the braking energy of the vehicle, the hydraulic oil of the hydraulic walking component 900 flows to the first accumulator 110 through the hydraulic control directional valve 220, which refers to the hydraulic oil on the high-pressure side of the hydraulic walking component 900.

[0048] Specifically, the first accumulator 110 is used to store hydraulic oil on the high-pressure side of the hydraulic travel assembly 900 during braking; the pressure control valve 210 is used to switch between a first opening state and a second opening state according to the vehicle's braking stroke, providing different braking pressures to the hydraulic control directional valve 220.

[0049] It should be noted that, in practice, the pressure control valve 210 is continuously proportionally controlled. That is, when the vehicle is in a slow braking stroke, the valve core position of the pressure control valve 210 is adjusted proportionally according to the change in the slow braking stroke. During the proportional adjustment process, the valve core position is always in the first opening state as long as it does not exceed the critical position. In other words, the first opening state can correspond to multiple continuously changing positions of the valve core to output different control oil pressures. That is, the low-pressure control oil proportionally adjusts the valve core position of the hydraulic directional valve 220, so that the hydraulic directional valve 220 is in a partially open state overall.

[0050] Furthermore, when the vehicle is in the emergency braking stroke, according to the change in the emergency braking stroke of the vehicle, the valve core position of the pressure control valve 210 is adjusted proportionally. The state in which the valve core position exceeds the critical position is the second opening state. That is, the second opening state can also correspond to multiple continuously changing positions of the valve core to output different control oil pressures. In other words, the high pressure control oil proportionally adjusts the valve core position of the hydraulic directional valve 220, so that the hydraulic directional valve 220 is in a fully open state.

[0051] It is understood that the critical position can be set according to the actual scenario, and the embodiments of this application do not impose any restrictions.

[0052] The hydraulic directional valve 220 is used to disconnect the high-pressure oil circuit on the high-pressure side of the hydraulic travel assembly 900 from the oil circuit connected to the first accumulator 110 when the vehicle is not braking, so as to prevent the hydraulic oil on the high-pressure side from entering the first accumulator 110 to fill when the hydraulic travel assembly 900 is working normally, which would affect the working efficiency of the hydraulic travel assembly 900; and, when the vehicle is braking, it is used to open the valve core by the braking pressure provided by the pressure control valve 210, so that the pressure oil of the hydraulic travel assembly 900 enters the first accumulator 110 for storage through the hydraulic directional valve 220.

[0053] The valve core opening of the hydraulic directional valve 220 is proportional to the braking pressure. When the vehicle is in the first braking stroke, that is, when the driver operates the brake pedal at a distance less than or equal to the preset distance and performs slow and stable braking, the pressure control valve 210 will be in the first opening state. Thus, the pressure oil stored in the first accumulator 110 is output as low-pressure control oil through the pressure control valve 210 to the control chamber of the hydraulic directional valve 220, providing a small switching control pressure for the hydraulic directional valve 220, so that the hydraulic directional valve 220 is in a partially open state. In this way, the hydraulic oil of the small flow hydraulic travel component 900 is stored in the first accumulator 110 through the hydraulic directional valve 220. This can avoid the sudden reduction of the effective flow of the hydraulic travel component 900 due to a large amount of hydraulic oil entering the first accumulator 110, which would cause the vehicle to brake suddenly and pose a safety hazard to the driver.

[0054] When the vehicle is in its second braking stroke, i.e., the distance the driver moves by controlling the brake pedal is greater than a preset distance, and emergency rapid braking is performed, the pressure control valve 210 will be in the second opening state. As a result, the pressure oil stored in the first accumulator 110 will be output as high-pressure control oil through the pressure control valve 210 to the control chamber of the hydraulic directional valve 220, providing a larger directional control pressure to the hydraulic directional valve 220, so that the hydraulic directional valve 220 is in the fully open state. In this way, the hydraulic oil of the large-flow hydraulic travel component 900 is stored in the first accumulator 110, reducing the pressure loss of the hydraulic oil through the hydraulic directional valve 220, so that the hydraulic oil of the hydraulic travel component 900 can enter the first accumulator 110 more efficiently and quickly for filling and storing energy.

[0055] It should be noted that the preset distance can be set and adjusted according to the actual situation, and this application embodiment will not elaborate on this further.

[0056] In specific implementation, the pressure control valve 210 of this application embodiment can be manually controlled, or it can be hydraulically controlled, electromagnetically controlled, or electro-hydraulic controlled, so that the pressure control valve 210 can provide different reversing control pressures to the hydraulically controlled reversing valve 220 according to the vehicle's braking stroke.

[0057] For example, the pressure control valve 210 includes a valve body, which includes a valve seat and a valve core disposed on the valve seat.

[0058] When the pressure control valve 210 is manually controlled, the valve core can be connected to the vehicle's brake pedal via a linkage mechanism. The linkage mechanism includes a connecting rod and a push rod connected to the connecting rod. The connecting rod is used to connect to the vehicle's brake pedal, and the push rod is connected to the valve core. Thus, when the driver presses the brake pedal, the brake pedal will be displaced, and the displacement will be transmitted to the valve core through the linkage mechanism, so that the valve core adjusts its position according to the magnitude of the brake pedal displacement, thereby realizing the switching of different opening states.

[0059] When the pressure control valve 210 is controlled by hydraulic control, the pressure control valve 210 may also include a spring and a hydraulic control chamber for adjusting the position of the valve core. The spring is used to set the initial position of the valve core. The hydraulic control chamber can be connected to external pressure oil through a hydraulic control port. In this way, when the driver presses the brake pedal, the brake pedal is displaced. According to the magnitude of the brake pedal displacement, different pressure oil is output and transmitted to the hydraulic control chamber of the pressure control valve 210, thereby adjusting the position of the valve core of the pressure control valve 210.

[0060] When the pressure control valve 210 is controlled electromagnetically, the pressure control valve 210 may also include a spring and an electromagnetic coil for generating a magnetic field to attract or repel the valve core. The electromagnetic coil can be connected to the vehicle's brake pedal via a control device 200. The control device 200 includes a controller and a stroke sensor that is communicatively connected to the controller. The controller is electrically connected to the electromagnetic coil. The stroke sensor is used to detect the travel of the brake pedal and outputs an electrical signal proportional to the travel to the controller, causing the controller to adjust the current of the electromagnetic coil according to the magnitude of the brake pedal displacement, thereby changing the position of the valve core by varying the strength of the magnetic field generated by the electromagnetic coil.

[0061] When the pressure control valve 210 is controlled electromagnetically, the electromagnetic coil acts on the hydraulic piston or diaphragm, which adjusts its position according to the magnetic field generated by the electromagnetic coil, thereby adjusting the position of the valve core.

[0062] The number of first accumulators 110 in this application embodiment can be set to one, and the vehicle braking energy can be recovered by one first accumulator 110. Of course, the number of first accumulators 110 can also be set to at least two. Two or more first accumulators 110 can increase the energy storage space and meet the storage of the large flow of hydraulic oil flowing in when the hydraulic walking component 900 brakes.

[0063] This application embodiment does not limit the specific number of hydraulically controlled directional valves 220. For example, the first accumulator 110 is configured as follows: Figure 1 Of the two shown, the hydraulic directional valve 220 can be set as follows: Figure 1 As shown, both first accumulators 110 are connected to the hydraulic walking assembly 900 through a hydraulically controlled directional valve 220; of course, the hydraulically controlled directional valve 220 can also be configured to correspond one-to-one with the first accumulator 110, so that the first accumulator 110 is connected to the hydraulic walking assembly 900 through the corresponding hydraulically controlled directional valve 220.

[0064] In summary, in the walking hydraulic system of this application embodiment, the pressure control valve 210 switches between a first opening state and a second opening state according to the vehicle's braking stroke. This allows the pressure oil in the first accumulator 110 to provide different reversing control pressures to the hydraulic directional valve 220, thereby proportionally adjusting the valve core position of the hydraulic directional valve 220. In the first opening state, corresponding to the vehicle's slow, light braking stroke, the pressure oil stored in the first accumulator 110 is output as low-pressure control oil through the pressure control valve 210 and flows into the control chamber of the hydraulic directional valve 220. This causes the hydraulic directional valve 220 to be partially open under the push of the low-pressure oil, thus preventing the first accumulator 110 from recovering a large flow of hydraulic oil from the hydraulic walking assembly 900 via the hydraulic directional valve 220, which would reduce the effective flow of the hydraulic walking assembly 900 and cause the vehicle to brake suddenly.

[0065] In the second opening state, corresponding to the vehicle's emergency braking stroke, the pressure oil stored in the first accumulator 110 is output as high-pressure control oil through the pressure control valve 210 and flows into the control chamber of the hydraulic directional valve 220. This causes the hydraulic directional valve 220 to be fully open under the push of the high-pressure oil, thereby avoiding insufficient hydraulic oil flow recovered by the first accumulator 110 to the hydraulic travel assembly 900 through the hydraulic directional valve 220, which would otherwise result in energy waste. With this design, the energy recovery of the hydraulic travel assembly 900 by the first accumulator 110 through the hydraulic directional valve 220 can be adapted to match the vehicle's braking stroke, resulting in good energy recovery effect without affecting the vehicle's braking performance.

[0066] See Figure 2 and Figure 4 In some embodiments, the energy storage assembly 100 further includes at least one second energy storage device 120, and the control device 200 further includes a control element 230 and a solenoid directional valve 240. The control element 230 is communicatively connected to the engine 930 of the hydraulic walking assembly 900 and is used to detect the rotational speed of the engine 930. The second energy storage device 120 is connected to the hydraulic walking assembly 900 through the solenoid directional valve 240. The control element 230 is configured to control the solenoid directional valve 240 to open when the engine 930 changes from a first rotational speed to a second rotational speed, so as to connect the hydraulic walking assembly 900 and the second energy storage device 120, so that the hydraulic oil of the hydraulic walking assembly 900 flows into the second energy storage device 120 through the solenoid directional valve 240. The first rotational speed is greater than the second rotational speed.

[0067] Here, when the engine 930 changes from the first speed to the second speed, and the first speed is greater than the second speed, that is, when the vehicle is in a deceleration condition, this embodiment of the application can reduce energy loss during vehicle operation by setting a second energy accumulator 120 to recover excess energy released when the vehicle decelerates, and the energy recovery of the hydraulic walking component 900 is more comprehensive.

[0068] Specifically, the control unit 230 is used to output control current to the solenoid directional valve 240 based on the detected engine speed information 930, thereby controlling the opening and closing of the solenoid directional valve 240.

[0069] For example, when the vehicle decelerates, the controller 230 sends a signal to open the valve core of the solenoid directional valve 240, thereby connecting the hydraulic oil of the hydraulic travel assembly 900 to the second accumulator 120 for energy storage. Further, it can be understood that when the vehicle accelerates or travels at a constant speed, the controller disconnects the control signal to the solenoid directional valve 240. The valve core of the solenoid directional valve 240 is reset under the action of spring force, closing its oil inlet and outlet, thereby disconnecting the oil circuit between the hydraulic travel assembly 900 and the second accumulator 120. This prevents the hydraulic oil of the hydraulic travel assembly 900 from entering the second accumulator 120 and filling it, thus affecting the working efficiency of the hydraulic travel assembly 900.

[0070] The specific number of the second accumulator 120 and the electromagnetic reversing valve 240 is not limited in this embodiment. For example, the second accumulator 120 can be set to one or more. When the second accumulator 120 is set to two or more, the electromagnetic reversing valve 240 can be set to one or correspond one-to-one with the second accumulator 120.

[0071] To achieve effective utilization of the energy recovered from the first accumulator 110 and the second accumulator 120, refer to... Figure 3 and Figure 4 In some embodiments, the walking hydraulic system further includes a brake 300, which is connected to the outlet of a pressure control valve 210. The outlet of at least one of the first accumulator 110 and the second accumulator 120 is connected to the inlet of the pressure control valve 210. The pressure control valve 210 is also used to, in the first opening state, output high-pressure control oil from the pressure oil in the first accumulator 110 and / or the pressure oil in the second accumulator 120 via the pressure control valve 210 to the brake 300.

[0072] In the second opening state, the pressure oil in the first accumulator 110 and / or the pressure oil in the second accumulator 120 is output as low-pressure control oil through the pressure control valve 210 and flows into the brake member 300; the brake member 300 is used to apply a first braking force to the brake disc of the hydraulic travel assembly 900 under the push of the high-pressure control oil, and to apply a second braking force to the brake disc of the hydraulic travel assembly 900 under the push of the low-pressure control oil; wherein the first braking force is greater than the second braking force.

[0073] With this configuration, when the vehicle brakes, the hydraulic oil stored in the hydraulic travel assembly 900 is recovered by at least one of the first accumulator 110 and the second accumulator 120 and used as a brake oil source. It can be further applied to the brake element 300 through the pressure control valve 210 and used as a brake oil source, thereby using the brake element 300 to brake the vehicle. As a result, the pump and filling valve used for braking in the vehicle itself can be eliminated, which helps to reduce costs and make the vehicle lighter.

[0074] Specifically, the brake component 300 receives pressurized oil and applies braking force to the brake disc of the hydraulic travel assembly 900 to achieve vehicle deceleration and braking. In practice, the brake component 300 applies different braking forces according to the pressure of the hydraulic oil to ensure that appropriate braking force can be provided to the brake disc under different braking strokes, thereby improving braking performance and safety under different driving conditions.

[0075] It should be noted that, in the specific implementation, such as Figure 1 and Figure 4 As shown, the pressure control valve 210 is also equipped with a hydraulic oil tank 270. Thus, after the brake pedal is released, the pressure oil in the brake component 300 enters the hydraulic oil tank 270 through the return port of the pressure control valve 210 for storage.

[0076] For example, the brake component 300 may include a brake cylinder and a brake caliper. The brake caliper is connected to the piston of the brake cylinder. The vehicle's brake disc is mounted on the vehicle's wheel axle. The brake disc is used to cooperate with the brake caliper to generate friction, thereby achieving vehicle braking. Thus, when low-pressure oil flows into the brake cylinder through the pressure control valve 210 and pushes the piston to move accordingly, the piston pushes the brake caliper according to the pressure of the low-pressure oil, applying a smaller braking force to the brake disc, i.e., a second braking force suitable for slow braking conditions. When high-pressure oil flows into the brake cylinder through the pressure control valve 210 and pushes the piston to move accordingly, the piston pushes the brake caliper according to the pressure of the high-pressure oil, applying a larger braking force to the brake disc, i.e., a first braking force suitable for emergency braking conditions.

[0077] It should be noted that, in this embodiment of the application, the vehicle can be braked by recovering the stored braking energy through the first accumulator 110, or by recovering the stored deceleration energy through the second accumulator 120, or by a combination of the two. This embodiment of the application does not limit this.

[0078] See Figure 4In some examples, the control device 200 further includes an electro-proportional directional valve 250 and a selector valve 260, the electro-proportional directional valve 250 being electrically connected to the control element 230; the outlets of the first accumulator 110 and the second accumulator 120 are both connected to the inlet of the electro-proportional directional valve 250, and the outlet of the electro-proportional directional valve 250 is connected to the high-pressure side of the hydraulic travel assembly 900 via the selector valve 260; the control element 230 is configured to, when the engine 930 changes from a third speed to a fourth speed, control the electro-proportional directional valve 250 to open, thereby connecting the first accumulator 110 and the high-pressure side of the hydraulic travel assembly 900, allowing hydraulic oil from the first accumulator 110 to flow to the high-pressure side of the hydraulic travel assembly 900 via the electro-proportional directional valve 250; and to, connect the second accumulator 120 and the high-pressure side of the hydraulic travel assembly 900, allowing hydraulic oil from the second accumulator 120 to flow to the high-pressure side of the hydraulic travel assembly 900 via the electro-proportional directional valve 250; wherein the third speed is less than the fourth speed.

[0079] Specifically, the electro-proportional directional valve 250 is used to release the hydraulic oil stored in the first accumulator 110 and the second accumulator 120 into the high-pressure side of the hydraulic travel assembly 900 when the engine 930 changes from the third speed to the fourth speed, thereby assisting the vehicle in traveling. In specific implementation, the third speed being less than the fourth speed can correspond to at least one of the vehicle's starting, acceleration, and uphill driving conditions.

[0080] This configuration reduces the load on the engine 930 of the hydraulic travel assembly 900, thereby reducing the power consumption of the engine 930 and the vehicle's fuel consumption.

[0081] By setting the selector valve 260, when the high-pressure side and low-pressure side of the vehicle's hydraulic travel assembly 900 are interchanged under different working conditions, the selector valve 260 can ensure that the hydraulic oil flowing out through the electro-proportional directional valve 250 can flow correctly into the high-pressure side of the hydraulic travel assembly 900, thereby providing power for the vehicle's starting, acceleration and climbing conditions.

[0082] like Figure 4 As shown, specifically, the selector valve 260 includes a first sub-outlet 4, a second sub-outlet 5, and an inlet 6. The inlet 6 is connected to the outlet of the electro-proportional directional valve 250. The first sub-outlet 4 is connected to the first side A of the hydraulic travel assembly 900, and the second sub-outlet 5 is connected to the second side B of the hydraulic travel assembly 900. The selector valve 260 is configured to connect the inlet 6 and the first sub-outlet 4 when the pressure on the first side A is greater than the pressure on the second side B; or, to connect the inlet 6 and the second sub-outlet 5 when the pressure on the second side B is greater than the pressure on the first side A.

[0083] In other words, when the first side A is the high-pressure side, the inlet 6 and the first sub-outlet 4 are connected by the action of the selector valve 260; when the second side B is the high-pressure side, the inlet 6 and the second sub-outlet are connected by the action of the selector valve 260; in this way, the hydraulic oil flowing out through the electro-proportional directional valve 250 can flow correctly into the high-pressure side of the hydraulic travel assembly 900 after passing through the selector valve 260, thereby driving the hydraulic motor 910 to accelerate rotation.

[0084] This application does not limit the specific type of the selection valve 260. Exemplarily, the selection valve 260 is configured as a pressure-sensitive directional valve. The pressure-sensitive directional valve may include a valve body, a valve core located within the valve body, and a pressure-balancing piston. A first sub-outlet 4, a second sub-outlet 5, and an inlet 6 are disposed on the valve body. The pressure-balancing piston is used to detect the pressure difference between the first side A and the second side B, and moves the valve core according to the pressure difference. Exemplarily, when the pressure on the first side A increases and exceeds the pressure on the second side B, the pressure-balancing piston moves the valve core towards the first sub-outlet 4, thus connecting the inlet 6 and the first sub-outlet 4.

[0085] Furthermore, the control unit 230 is also configured to send a first command to the electro-proportional directional valve 250 to increase the valve core opening of the electro-proportional directional valve 250 when the difference between the fourth speed and the third speed is detected to be greater than a preset value; and to send a second command to the electro-proportional directional valve 250 to decrease the valve core opening of the electro-proportional directional valve 250 when the difference between the fourth speed and the third speed is detected to be less than or equal to a preset value.

[0086] Specifically, the control unit 230 sends a corresponding proportional signal to the electro-proportional directional valve 250 according to the rate of increase of the engine speed 930. This allows the electro-proportional directional valve 250 to control the release of hydraulic oil stored in the first accumulator 110 and the second accumulator 120 into the high-pressure side of the hydraulic travel assembly 900 at different valve openings during starting, acceleration, and uphill conditions. In this way, it can quickly respond to changes in the engine speed 930, improve the response speed of the entire system, and optimize the vehicle's performance during starting, acceleration, and uphill conditions.

[0087] For example, when the vehicle is going uphill and starting, the engine 930 changes from the third speed to the fourth speed, and the difference between the fourth speed and the third speed is greater than a preset value, that is, the engine 930 shows a rapid increase in speed. The control unit 230 sends a first command, namely a high current signal, to the electro-proportional directional valve 250, so that the valve core of the electro-proportional directional valve 250 opens more. In this way, the hydraulic oil stored in the first accumulator 110 and the second accumulator 120 can be released quickly and replenished to the high-pressure side of the hydraulic travel assembly 900, driving the hydraulic motor 910 of the hydraulic travel assembly 900 to rotate, so that the hydraulic motor 910 can quickly complete the start-up and hill climbing.

[0088] When the vehicle accelerates, the difference between the fourth and third speeds of the engine 930 is less than or equal to a preset value, meaning that the engine 930 exhibits a slower speed increase. The control unit 230 sends a second command, namely a small current signal, to the electro-proportional directional valve 250, causing the valve core of the electro-proportional directional valve 250 to open less. As a result, the hydraulic oil stored in the first accumulator 110 and the second accumulator 120 can be slowly released and replenished to the high-pressure side of the hydraulic travel assembly 900, driving the hydraulic motor 910 of the hydraulic travel assembly 900 to rotate, enabling the hydraulic motor 910 to slowly complete the acceleration.

[0089] It is understood that the preset value can be set according to the actual situation, and this application embodiment will not elaborate on this.

[0090] See 2 to Figure 4 In some examples, the walking hydraulic system also includes a first check valve 400 and a second check valve 500. The first check valve 400 is located between the hydraulically controlled directional valve 220 and the first accumulator 110, and the outlet of the hydraulically controlled directional valve 220 is connected to the inlet of the first accumulator 110 through the first check valve 400. The second check valve 500 is located between the solenoid directional valve 240 and the second accumulator 120, and the outlet of the solenoid directional valve 240 is connected to the inlet of the second accumulator 120 through the second check valve 500.

[0091] With the above settings, when the oil pressure stored in the first accumulator 110 and the second accumulator 120 is higher than that of the hydraulic travel assembly 900, the first check valve 400 and the second check valve 500 can ensure that the hydraulic oil stored in the first accumulator 110 and the second accumulator 120 will not flow back into the hydraulic travel assembly 900, thus avoiding affecting the vehicle's braking and deceleration.

[0092] See 2 to Figure 4 In some embodiments, the walking hydraulic system further includes a third check valve 600 and a fourth check valve 700. The outlets of the first accumulator 110 and the second accumulator 120 are both connected to the inlet of the pressure control valve 210. The outlet of the first accumulator 110 is connected to the inlet of the pressure control valve 210 through the third check valve 600, and the outlet of the second accumulator 120 is connected to the inlet of the pressure control valve 210 through the fourth check valve 700.

[0093] Thus, by setting the third check valve 600 and the fourth check valve 700 to isolate the oil circuits of the first accumulator 110 and the second accumulator 120, the operation of the other oil circuit will not be affected if the oil circuit of one of the first accumulator 110 and the second accumulator 120 is accidentally damaged.

[0094] For example, by setting a fourth check valve 700, when the vehicle brakes, it can be ensured that the hydraulic oil of the hydraulic travel assembly 900 can be stored in the first accumulator 110, and the hydraulic oil is prevented from further entering the second accumulator 120 through the first accumulator 110, which would cause the pressure of the second accumulator 120 to be too high and unable to store and recover the energy released by the hydraulic travel assembly 900 when the vehicle decelerates, resulting in energy waste.

[0095] By setting a third one-way valve 600, when braking the vehicle solely through the second accumulator 120, it is possible to prevent the second accumulator 120 from being connected to the first accumulator 110, which would cause the hydraulic oil in the second accumulator 120 to flow into the first accumulator 110, resulting in a lower pressure in the second accumulator 120 that cannot meet the pressure requirements of the vehicle during braking and thus affecting the vehicle's braking performance.

[0096] Continue reading 2 to 3 Figure 4 In some examples, the travel hydraulic system also includes a pressure shut-off valve assembly 800, which includes a first pressure shut-off valve 810 and a second pressure shut-off valve 820. The first pressure shut-off valve 810 is located between a first check valve 400 and a first accumulator 110, with the outlet of the first check valve 400 connected to the inlet of the first pressure shut-off valve 810 and the outlet of the first pressure shut-off valve 810 connected to the inlet of the first accumulator 110. The second pressure shut-off valve 820 is located between a second check valve 500 and a second accumulator 120, with the outlet of the second check valve 500 connected to the inlet of the second pressure shut-off valve 820 and the outlet of the second pressure shut-off valve 820 connected to the inlet of the second accumulator 120.

[0097] Specifically, by setting a first pressure cut-off valve 810, when the braking energy is recovered, when the filling pressure in the first accumulator 110 reaches the threshold pressure set by the first pressure cut-off valve 810, the valve core of the first pressure cut-off valve 810 closes to stop the filling, preventing the hydraulic oil of the hydraulic walking assembly 900 from continuing to fill the first accumulator 110 and causing damage to the accumulator, thus ensuring the safety and reliability of the first accumulator 110.

[0098] By setting a second pressure shut-off valve 820, when the deceleration energy is recovered, when the filling pressure in the second accumulator 120 reaches the threshold pressure set by the second pressure shut-off valve 820, the valve core of the second pressure shut-off valve 820 closes to stop filling, preventing the hydraulic oil of the hydraulic walking assembly 900 from continuing to fill the second accumulator 120 and causing damage to the second accumulator 120, thus ensuring the safety and reliability of the second accumulator 120.

[0099] This application also provides an engineering vehicle, including a vehicle body and a walking hydraulic system as described in any of the above embodiments, which is mounted on the vehicle body.

[0100] The overall structure and working principle of the walking hydraulic system are the same as those in the aforementioned embodiments, and will not be repeated here.

[0101] In a specific implementation, the hydraulic walking assembly 900 includes, for example: Figure 1 The engine 930, hydraulic pump 920, hydraulic motor 910 and shuttle valve 940 are shown. The engine 930 drives the hydraulic pump 920 to output high-pressure oil, which in turn drives the hydraulic motor 910 to rotate. The outlet of the hydraulic motor 910 is connected to the inlet of the hydraulic control directional valve 220 of the control device 200 through the shuttle valve 940.

[0102] Specifically, the engine 930 provides power input to the hydraulic travel assembly 900; the hydraulic pump 920 provides pressurized oil to the hydraulic travel assembly 900. In practice, for example... Figure 4 As shown, the hydraulic pump 920 is equipped with a hydraulic oil tank 270, which is used to store and provide hydraulic oil required by the hydraulic travel assembly 900.

[0103] The hydraulic motor 910 is used to drive the vehicle's drive system when it rotates, thereby enabling the vehicle to move; the shuttle valve 940 is used to select the connection between the high-pressure side of the hydraulic drive assembly 900 and the inlet of the hydraulic control directional valve 220, allowing the hydraulic oil of the hydraulic drive assembly 900 to enter the first accumulator 110 for storage; for example, as Figure 4 As shown, when the first side A of the hydraulic walking assembly 900 is the high-pressure side, the inlet 1 and outlet 3 of the shuttle valve 940 are connected, and when the second side B of the hydraulic walking assembly 900 is the high-pressure side, the inlet 2 and outlet 3 of the shuttle valve 940 are connected.

[0104] The engineering vehicle in this application embodiment, by setting a walking hydraulic system, can achieve a good energy recovery effect on the vehicle, and at the same time recovering energy, it will not affect the braking effect of the vehicle.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A hydraulic system for walking, characterized in that, The hydraulic walking assembly (900), the energy storage assembly (100) and the control device (200) are included. The energy storage assembly (100) includes at least one first accumulator (110), and the control device (200) includes a pressure control valve (210) and a hydraulic control reversing valve (220); the first accumulator (110) is connected with the hydraulic walking assembly (900) through the hydraulic control reversing valve (220), the pressure control valve (210) is connected with the first accumulator (110), and the hydraulic control reversing valve (220) is connected with the pressure control valve (210). The pressure control valve (210) is used for switching between a first opening state and a second opening state according to a brake stroke of the vehicle, wherein, in the first opening state, pressure oil stored in the first accumulator (110) is output as low-pressure control oil into a control cavity of the hydraulic control reversing valve (220) through the pressure control valve (210), and in the second opening state, the pressure oil stored in the first accumulator (110) is output as high-pressure control oil into the control cavity of the hydraulic control reversing valve (220) through the pressure control valve (210). The hydraulic control reversing valve (220) is used for being in a partially open state under the pushing of the low-pressure control oil and being in a fully open state under the pushing of the high-pressure control oil, so as to adjust the flow of hydraulic oil of the hydraulic walking assembly (900) to the first accumulator (110) through the hydraulic control reversing valve (220).

2. The hydraulic travel system of claim 1, wherein, The energy storage assembly (100) further includes at least one second accumulator (120), and the control device (200) further includes a control member (230) and an electromagnetic reversing valve (240); the control member (230) is communicatively connected with an engine (930) of the hydraulic walking assembly (900), and is used for detecting a rotating speed of the engine (930); the second accumulator (120) is connected with the hydraulic walking assembly (900) through the electromagnetic reversing valve (240). The control member (230) is configured to control the electromagnetic reversing valve (240) to open when the engine (930) changes from a first rotating speed to a second rotating speed, so as to connect the hydraulic walking assembly (900) and the second accumulator (120), and make the hydraulic oil of the hydraulic walking assembly (900) flow into the second accumulator (120) through the electromagnetic reversing valve (240); wherein the first rotating speed is greater than the second rotating speed.

3. The hydraulic travel system of claim 2, wherein, A brake member (300) is further included, the brake member (300) is connected with an outlet of the pressure control valve (210), and an inlet of the pressure control valve (210) is connected with an outlet of at least one of the first accumulator (110) and the second accumulator (120). The pressure control valve (210) is also used to output low-pressure control oil to the brake (300) via the pressure control valve (210) when the first opening state is in the first accumulator (110) and / or the second accumulator (120) pressure oil; in the second opening state, the pressure oil in the first accumulator (110) and / or the second accumulator (120) is output to the brake (300) via the pressure control valve (210) after the high-pressure control oil; The brake (300) is used to apply a first brake force to the brake disc of the hydraulic walking assembly (900) under the push of the high-pressure control oil, and a second brake force to the brake disc of the hydraulic walking assembly (900) under the push of the low-pressure control oil; wherein the first brake force is greater than the second brake force.

4. The hydraulic travel system of claim 2, wherein, The control device (200) further comprises an electric proportional directional valve (250) and a selection valve (260), the electric proportional directional valve (250) is electrically connected with the control (230); The outlet of the first accumulator (110) and the second accumulator (120) is connected with the inlet of the electric proportional directional valve (250), and the outlet of the electric proportional directional valve (250) is connected with the high-pressure side of the hydraulic walking assembly (900) through the selection valve (260); The control (230) is configured to control the electric proportional directional valve (250) to open when the engine (930) is changed from a third speed to a fourth speed, to connect the first accumulator (110) and the high-pressure side of the hydraulic walking assembly (900), and to make the hydraulic oil of the first accumulator (110) flow to the high-pressure side of the hydraulic walking assembly (900) via the electric proportional directional valve (250), and to connect the second accumulator (120) and the high-pressure side of the hydraulic walking assembly (900), and to make the hydraulic oil of the second accumulator (120) flow to the high-pressure side of the hydraulic walking assembly (900) via the electric proportional directional valve (250); wherein the third speed is less than the fourth speed.

5. The hydraulic travel system of claim 4, wherein, The control (230) is further configured to send a first instruction to the electric proportional directional valve (250) to increase the valve core opening of the electric proportional directional valve (250) when it is detected that the difference between the fourth speed and the third speed is greater than a preset value; And when it is detected that the difference between the fourth speed and the third speed is less than or equal to a preset value, a second instruction is sent to the electric proportional directional valve (250) to reduce the valve core opening of the electric proportional directional valve (250).

6. The hydraulic travel system of claim 4, wherein, The selection valve (260) comprises a first sub-outlet, a second sub-outlet and an inlet, the inlet is connected with the outlet of the electric proportional directional valve (250), the first sub-outlet is connected with the first side of the hydraulic walking assembly (900), and the second sub-outlet is connected with the second side of the hydraulic walking assembly (900); The selection valve (260) is configured to connect the inlet and the first sub-outlet when the pressure on the first side is greater than the pressure on the second side, or to connect the inlet and the second sub-outlet when the pressure on the second side is greater than the pressure on the first side.

7. A hydraulic travel system according to any one of claims 2 to 6, wherein Further comprising a first check valve (400) and a second check valve (500), the first check valve (400) is located between the hydraulic control reversing valve (220) and the first accumulator (110), the outlet of the hydraulic control reversing valve (220) is connected with the inlet of the first accumulator (110) through the first check valve (400); The second check valve (500) is located between the electromagnetic reversing valve (240) and the second accumulator (120), the outlet of the electromagnetic reversing valve (240) is connected with the inlet of the second accumulator (120) through the second check valve (500).

8. The hydraulic system of any one of claims 3 to 6, wherein, Further comprising a third check valve (600) and a fourth check valve (700), the outlet of the first accumulator (110) and the outlet of the second accumulator (120) are both connected with the inlet of the pressure control valve (210); The outlet of the first accumulator (110) is connected with the inlet of the pressure control valve (210) through the third check valve (600), and the outlet of the second accumulator (120) is connected with the inlet of the pressure control valve (210) through the fourth check valve (700).

9. The hydraulic travel system of claim 7, wherein, Further comprising a pressure cut-off valve assembly (800), the pressure cut-off valve assembly (800) comprises a first pressure cut-off valve (810) and a second pressure cut-off valve (820); The first pressure cut-off valve (810) is located between the first check valve (400) and the first accumulator (110), the outlet of the first check valve (400) is connected with the inlet of the first pressure cut-off valve (810), and the outlet of the first pressure cut-off valve (810) is connected with the inlet of the first accumulator (110); The second pressure cut-off valve (820) is located between the second check valve (500) and the second accumulator (120), the outlet of the second check valve (500) is connected with the inlet of the second pressure cut-off valve (820), and the outlet of the second pressure cut-off valve (820) is connected with the inlet of the second accumulator (120).

10. An engineering vehicle characterized by, A vehicle body and a traveling hydraulic system as claimed in any one of claims 1 to 9 disposed on the vehicle body.

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