Closed hydraulic system multi-stage pressure unauthorized control valve group, hydraulic system and road maintenance vehicle

Abstract

The utility model provides a closed hydraulic system multi-stage pressure unauthorized control valve set, a hydraulic system and a road maintenance vehicle, and the control valve set comprises a first branch assembly which is provided with an oil inlet MA, a throttling valve A, a two-position three-way electromagnetic valve A, a two-position four-way electromagnetic valve A, a sequence valve A, a sequence valve B, a one-way valve A, a one-way valve B, an output oil port X3B and an output oil port X3A; the sequence valve A is connected with the output oil port X3A and the output oil port X3B through the one-way valve A and the one-way valve B. The sequence valve B is connected with the output oil port X3A and the output oil port X3B through the one-way valve A and the one-way valve B. The second branch assembly is provided with an oil inlet MB, a throttling valve B, a two-position three-way electromagnetic valve B, a two-position four-way electromagnetic valve B, a sequence valve C, a sequence valve D, a one-way valve C, a one-way valve D, an oil output port X4A and an oil output port X4B, the sequence valve C is connected with the oil output port X4A and the oil output port X4B through the one-way valve C and the one-way valve D, and the sequence valve D is connected with the oil output port X4A and the oil output port X4B through the one-way valve C and the one-way valve D. Compared with an existing control valve set, the application range of the control valve set can be greatly widened.

Description

Technical Field

[0001] This application relates to the field of closed hydraulic system control valve assembly technology, and in particular to a closed hydraulic system multi-stage pressure overriding control valve assembly, a hydraulic system, and a road maintenance vehicle. Background Technology

[0002] When large track maintenance machinery operates in sections using hydraulic drive, the maximum operating speed can reach about 80-100 km / h. During operation, if the speed control handle is suddenly pulled back or when running on a long slope, the hydraulic motor and hydraulic pump will switch working conditions due to the vehicle's inertia. The reverse pressure will drag the engine, causing the engine to run away or damaging the hydraulic components of the travel drive circuit, affecting the normal travel function of the whole vehicle, and even threatening the safety of track operation.

[0003] The existing solution is to connect the inlet of the reverse pressure control valve group to the pressure output port of the hydraulic pump, and the outlet of the valve group to the oil port of the hydraulic pump variable control mechanism. When the reverse pressure reaches the set value, the reverse pressure control valve group outputs control oil to increase the displacement of the hydraulic pump, absorb the reverse pressure, and avoid the above-mentioned risks.

[0004] However, when large road maintenance machinery is in a non-high-speed travel condition, if the high-speed travel motor does not adopt a forced large displacement scheme and uses the same system for work travel drive, the high-speed travel hydraulic pump can only be switched to a closed working system with non-overlapping working conditions and a rated pressure greater than or equal to the pump's rated pressure, or even left idle, resulting in a narrow range of applications. Summary of the Invention

[0005] To address one of the aforementioned technical deficiencies, this application provides a closed-loop hydraulic system multi-stage pressure overriding control valve group, a hydraulic system, and a road maintenance vehicle.

[0006] The first aspect of this application provides a multi-stage pressure overriding control valve assembly for a closed hydraulic system, comprising:

[0007] Valve body;

[0008] The first branch assembly is disposed on the valve body. The first branch assembly is provided with an oil inlet MA, a throttle valve A, a two-position three-way solenoid valve A, a two-position four-way solenoid valve A, a first sequence valve group, a first check valve group, and an output oil port X3B and an output oil port X3A in sequence from upstream to downstream. The first sequence valve group includes a sequence valve A and a sequence valve B, and the first check valve group includes a check valve A and a check valve B. The sequence valve A is connected to the output oil ports X3A and X3B through the check valves A and B, and the sequence valve B is connected to the output oil ports X3A and X3B through the check valves A and B. The pressure of the sequence valves A and B is adjustable.

[0009] The second branch assembly is disposed on the valve body. The second branch assembly is provided with an oil inlet MB, a throttle valve B, a two-position three-way solenoid valve B, a two-position four-way solenoid valve B, a second sequence valve group, a second check valve group, and an output oil port X4A and an output oil port X4B in sequence from upstream to downstream. The second sequence valve group includes a sequence valve C and a sequence valve D. The second check valve group includes a check valve D and a check valve C. The sequence valve C is connected to the output oil ports X4A and X4B through the check valves C and D. The sequence valve D is connected to the output oil ports X4A and X4B through the check valves C and D. The pressure of the sequence valves C and D is adjustable.

[0010] Specifically, when the two-position four-way solenoid valve A is de-energized, the output port of the two-position three-way solenoid valve A is connected to the input port of the sequence valve A. When the two-position four-way solenoid valve B is de-energized, the output port of the two-position three-way solenoid valve B is connected to the input port of the sequence valve C. The set pressure of the sequence valves A and C is the maximum reverse hydraulic pressure under high-speed travel conditions. When the two-position four-way solenoid valve A is energized, the output port of the two-position three-way solenoid valve A is connected to the input port of the sequence valve B. When the two-position four-way solenoid valve B is energized, the output port of the two-position three-way solenoid valve B is connected to the input port of the sequence valve D. The set pressure of the sequence valves B and D is the maximum output pressure of the hydraulic pump under non-high-speed travel conditions.

[0011] Optionally, a two-position two-way solenoid valve A is installed between the downstream output port X3A of check valve A and the downstream output port X4A of check valve C, and a two-position two-way solenoid valve B is installed between the downstream output port X3B of check valve B and the downstream output port X4B of check valve D.

[0012] When the two-position two-way solenoid valve A is de-energized, the output port X3A and the output port X4A are connected. When the two-position two-way solenoid valve B is de-energized, the output port X3B and the output port X4B are connected.

[0013] Optionally, a shuttle valve is connected downstream of sequence valves A and B, as well as downstream of sequence valves C and D. A relief valve is connected downstream of the shuttle valve, and the pressure of the relief valve is adjustable.

[0014] Optionally, the overflow valve is also connected to the K3 pressure test port;

[0015] The two-position four-way solenoid valve A is connected to the pressure measuring port K2;

[0016] The two-position four-way solenoid valve B is connected to the pressure test port K1.

[0017] Optionally, the throttle valve A is an adjustable throttle valve or a fixed throttle orifice;

[0018] The throttle valve B is an adjustable throttle valve or a fixed throttle orifice.

[0019] Optionally, the oil inlet MA and the oil inlet MB are respectively connected to the main oil port A and the main oil port B of the hydraulic system drive circuit.

[0020] A second aspect of this application provides a hydraulic system including the aforementioned closed-loop hydraulic system multi-stage pressure overriding control valve group.

[0021] A third aspect of this application provides a road maintenance vehicle, including a frame and the aforementioned hydraulic system mounted on the frame.

[0022] By adopting the above technical solution, this application has the following beneficial effects:

[0023] The closed-loop hydraulic system multi-stage pressure overriding control valve group provided in this application adds a two-position four-way solenoid directional valve between a two-position three-way solenoid valve and a downstream sequence valve. At the same time, another sequence valve is connected in parallel at the original sequence valve position. The input end of the two-position four-way solenoid directional valve is connected to the output end of the two-position three-way solenoid valve, and the output end is connected to the two sets of sequence valves respectively. By setting the pressure value of the sequence valves separately, the pump can be used in systems with non-overlapping working conditions and inconsistent pressures, thereby increasing the applicability of the valve group.

[0024] The multi-stage pressure overriding control valve group for closed hydraulic systems provided in this application allows for overriding control of the closed hydraulic system when the same pump source is used in systems with different rated pressures. This limits the system's reverse pressure or the maximum output working pressure of the hydraulic pump, enabling shared use of the pump source within a wide pressure range. This ensures the safe operation of large road maintenance machinery and prevents the working system from overpressure. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 The diagram shows the hydraulic working principle of a multi-stage pressure overriding control valve group in a closed hydraulic system in the present technology.

[0027] Figure 2 This is a front view schematic diagram of the multi-stage pressure overriding control valve group of the closed hydraulic system provided in the embodiments of this application;

[0028] Figure 3 This is a top view of the multi-stage pressure overriding control valve group of the closed hydraulic system provided in the embodiments of this application.

[0029] Figure 4 This is a side view of the multi-stage pressure overriding control valve group of the closed hydraulic system provided in the embodiments of this application;

[0030] Figure 5 The diagram shows a rear view of the multi-stage pressure overriding control valve group of the closed hydraulic system provided in the embodiments of this application.

[0031] Figure reference numerals: 1. Throttling valve A; 2. Two-position three-way solenoid valve A; 3. Two-position four-way solenoid valve A; 4. Sequence valve A; 5. Sequence valve B; 6. Relief valve; 7. Check valve A; 8. Check valve B; 9. Two-position two-way solenoid valve A; 10. Two-position two-way solenoid valve B; 11. Shuttle valve; 12. Check valve C; 13. Check valve D; 14. Sequence valve D; 15. Sequence valve C; 16. Two-position four-way solenoid valve B; 17. Two-position three-way solenoid valve B; 18. Throttling valve B; 19. Valve body; 20. Oil inlet MA; 21. Oil inlet MB; 23. Oil outlet X3A; 24. Oil outlet X4A; 25. Oil outlet X3B; 26. Oil outlet X4B; 27. K1 pressure test port; 28. K2 pressure test port; 29. ​​K3 pressure test port. Detailed Implementation

[0032] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0033] In the description of this application and its embodiments, it should be understood that the indicated orientation or positional relationship terms are based only on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0034] In this application and its embodiments, unless otherwise expressly specified and limited, the terms "set," "install," "connect," "link," "fix," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to 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.

[0035] In this application and its embodiments, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] Example 1

[0037] See Figures 1 to 5 As shown, this embodiment provides a multi-stage pressure overriding control valve assembly for a closed hydraulic system, including a valve body 19, a first branch assembly, and a second branch assembly.

[0038] The first branch assembly is disposed on the valve body 19. The first branch assembly is provided with an oil inlet MA20, a throttle valve A1, a two-position three-way solenoid valve A2, a two-position four-way solenoid valve A3, a first sequence valve group, a first check valve group, and an output oil port X3B25 and an output oil port X3A23 in sequence from upstream to downstream. The first sequence valve group includes a sequence valve A4 and a sequence valve B5. The first check valve group includes a check valve A7 and a check valve B8. The sequence valve A4 is connected to the output oil port X3A23 and the output oil port X3B25 through the check valves A7 and B8. The sequence valve B5 is connected to the output oil port X3A23 and the output oil port X3B25 through the check valves A7 and B8.

[0039] The second branch assembly is disposed on the valve body 19. The second branch assembly is provided from upstream to downstream as follows: oil inlet MB21, throttle valve B18, two-position three-way solenoid valve B17, two-position four-way solenoid valve B16, second sequence valve group, second check valve group, and output oil port X4A24 and output oil port X4B26. The second sequence valve group includes sequence valve C15 and sequence valve D14. The second check valve group includes check valve C12 and check valve D13. The sequence valve C15 is connected to output oil port X4A24 and output oil port X4B26 through check valve C12 and check valve D13. The sequence valve D14 is connected to output oil port X4A24 and output oil port X4B26 through check valve C12 and check valve D13.

[0040] Specifically, when the 2-position 4-way solenoid valve A3 is de-energized, the output port of the 2-position 3-way solenoid valve A2 is connected to the input port of the sequence valve A4. When the 2-position 4-way solenoid valve B16 is de-energized, the output port of the 2-position 3-way solenoid valve B17 is connected to the input port of the sequence valve C15. The set pressure of the sequence valves A4 and C15 is the maximum reverse hydraulic pressure under high-speed driving conditions. The set pressure of the sequence valves, which is the maximum reverse hydraulic pressure under high-speed driving conditions, can be adjusted according to the requirements of the vehicle.

[0041] When the 2-position 4-way solenoid valve A3 is energized, the output port of the 2-position 3-way solenoid valve A2 is connected to the input port of the sequence valve B5. When the 2-position 4-way solenoid valve B16 is energized, the output port of the 2-position 3-way solenoid valve B17 is connected to the input port of the sequence valve D14. The set pressure of the sequence valves B5 and D14 is the maximum output pressure of the hydraulic pump under non-high-speed driving conditions. The set pressure of the sequence valves is the maximum output pressure of the hydraulic pump under non-high-speed driving conditions, which can be adjusted according to the requirements of the vehicle.

[0042] The closed-loop hydraulic system multi-stage pressure overriding control valve group provided in this application adds a two-position four-way solenoid directional valve between a two-position three-way solenoid valve and a downstream sequence valve. At the same time, another sequence valve is connected in parallel at the original sequence valve position. The input end of the two-position four-way solenoid directional valve is connected to the output end of the two-position three-way solenoid valve, and the output end is connected to the two sets of sequence valves respectively. By setting the pressure value of the sequence valves separately, the pump can be used in systems with non-overlapping working conditions and inconsistent pressures, thereby increasing the applicability of the valve group.

[0043] The multi-stage pressure overriding control valve group for closed hydraulic systems provided in this application allows for overriding control of the closed hydraulic system when the same pump source is used in systems with different rated pressures. This limits the system's reverse pressure or the maximum output working pressure of the hydraulic pump, enabling shared use of the pump source within a wide pressure range. This ensures the safe operation of large road maintenance machinery and prevents the working system from overpressure.

[0044] The check valve ensures that pressurized oil can only flow out from output ports X3A23 and X3B25 or output ports X4A24 and X4B26, while ensuring that the two sets of output ports X3A23, X3B25, X4A24, and X4B26 are independent and do not affect each other, thus enabling the control of one pump or the simultaneous control of two pumps.

[0045] In some possible implementations, a two-position two-way solenoid valve A9 is installed between the downstream output port X3A23 of check valve A7 and the downstream output port X4A24 of check valve C12, and a two-position two-way solenoid valve B10 is installed between the downstream output port X3B25 of check valve B8 and the downstream output port X4B26 of check valve D13. When the two-position two-way solenoid valve A9 is de-energized, output ports X3A23 and X4A24 are connected; when the two-position two-way solenoid valve B10 is de-energized, output ports X3B25 and X4B26 are connected. Since the pressure at both ends of the variable displacement cylinder of the hydraulic pump is the same, variable displacement control is not possible, and the hydraulic pump has no flow output. When the vehicle is stopped or the working device is not started, this prevents vehicle movement or working device malfunction due to pump failure, thus improving safety.

[0046] In some possible implementations, shuttle valves 11 are connected downstream of sequence valves A4 and B5, as well as downstream of sequence valves C15 and D14. A relief valve 6 is connected downstream of shuttle valves 11, and the pressure of the relief valve 6 is adjustable. Regardless of which branch contains pressurized oil, the pressurized oil will reach the inlet of the relief valve 6 through shuttle valves 11. When the pressure of the pressurized oil reaches the set pressure of the relief valve 6, it begins to overflow, thereby limiting the maximum pressure of the pressurized oil downstream of sequence valves A4, B5, C15, and D14 to not exceeding the set pressure range of the relief valve 6.

[0047] In some possible implementations, the overflow valve 6 is also connected to pressure test port 29 (K3), the two-position four-way solenoid valve A3 is connected to pressure test port 28 (K2), and the two-position four-way solenoid valve B16 is connected to pressure test port 27 (K1). This allows for the detection of the working pressures at pressure test ports 27 (K1), 28 (K2), and 29 (K3). This ensures the stability of the control valve assembly and facilitates understanding of its operating conditions.

[0048] In some possible implementations, the throttle valve A1 is an adjustable throttle valve or a fixed orifice, and the throttle valve B18 is also an adjustable throttle valve or a fixed orifice. An adjustable throttle valve has a regulating function, allowing the flow rate of the fluid to be adjusted by changing the position of the valve core. It is typically equipped with a handwheel or other adjusting mechanism, allowing the operator to easily adjust the valve opening to control the flow rate. This regulating function makes adjustable throttle valves suitable for systems requiring frequent flow rate adjustments. A fixed orifice has a relatively simple function, primarily limiting the fluid flow rate through its fixed orifice diameter. Because its flow rate is preset and not adjustable, a fixed orifice is suitable for applications requiring relatively stable flow rates. The choice can be made according to specific needs.

[0049] In some possible implementations, the oil inlet MA20 and the oil inlet MB21 are respectively connected to the main oil port A and the main oil port B of the hydraulic system drive circuit.

[0050] Example 2

[0051] See Figure 1-5 As shown, this embodiment provides a control method for a multi-stage pressure overriding control valve group in a closed hydraulic system as described in Embodiment 1, including:

[0052] a1. During high-speed travel, the oil inlet MA20 and MB21 are connected to the high-pressure side and low-pressure side of the main circuit of the travel system. By controlling the on / off state of the two-position three-way solenoid valve, the oil on the low-pressure side reaches the sequence valve through the throttle valve, the two-position three-way solenoid valve and the two-position four-way solenoid valve, while the oil on the high-pressure side is not connected to the sequence valve.

[0053] b1. When the vehicle is decelerated by pulling back the travel handle or running on a long slope, the operating conditions of the pump and motor in the travel circuit change, and the pressure on the high-pressure side and low-pressure side of the system also changes. The original low-pressure side pressure increases, and the travel drive circuit generates reverse pressure, so the speed of the vehicle will gradually decrease or the speed will no longer increase.

[0054] c1. When the pressure on the original low-pressure side rises to the set pressure of the sequence valve, the sequence valve is turned on, and the pressure oil enters the variable control cylinder of the hydraulic pump to overtake the pump's displacement and increase rapidly, thereby absorbing the output flow of the hydraulic motor and keeping the pressure on the original low-pressure side from rising further.

[0055] d1. When the vehicle speed drops to a certain value, the low-pressure side pressure will drop below the opening pressure of the sequence valve, at which point the sequence valve will close, and the hydraulic pump displacement will return to the original state controlled by the travel handle.

[0056] In some possible implementations, the control method for the multi-stage pressure overriding control valve group of the closed hydraulic system includes:

[0057] a2. During non-high-speed travel, the oil inlet MA20 and MB21 are connected to the high-pressure side and low-pressure side of the main circuit of the travel system. By controlling the on / off state of the two-position three-way solenoid valve, the oil on the high-pressure side reaches the sequence valve through the throttle valve, the two-position three-way solenoid valve and the two-position four-way solenoid valve, while the oil on the low-pressure side is not connected to the sequence valve.

[0058] b2. When the working system is operating normally, the system pressure is lower than the set pressure of the sequence valve, and the hydraulic pump displacement is consistent with the given displacement.

[0059] c2. When the working system encounters an impact or the motor is affected by an external load and the pressure rises to the set pressure of the sequence valve, the sequence valve is opened, and the pressure oil enters the variable control cylinder of the hydraulic pump to control the pump's displacement to decrease rapidly. The pump output flow decreases, and the pressure of the closed working system decreases. When it drops below the opening pressure of the sequence valve, the sequence valve closes, and the hydraulic pump displacement returns to the given displacement. This limits the maximum pressure of the closed working system to be consistent with the rated pressure of the sequence valve, protects the hydraulic components from damage, and enables the use of pump sources for different pressure ranges.

[0060] In some possible implementations, the control method for the multi-stage pressure overriding control valve group of the closed hydraulic system is characterized in that, under high-speed driving conditions, the two-position three-way solenoid valve A2 or the two-position three-way solenoid valve B17 controls the connection or disconnection of the input port with the subsequent channel through de-energization or energization logic. When the two-position three-way solenoid valve A2 is de-energized, the two-position four-way solenoid valve A3 is de-energized, or the two-position three-way solenoid valve B17 is de-energized, and the two-position four-way solenoid valve B16 is de-energized, the pressure at the inlet of the sequence valve A4 or the sequence valve C15 is... When the pressure reaches its set opening pressure, sequence valve A4 or sequence valve C15 will be turned on. The pressurized oil passes through sequence valve A4 or sequence valve C15 and the subsequent check valves A7, B8, C12, or D13 to reach output ports X3A23, X3B25, X4A24, or X4B26, thereby entering the variable mechanism of the hydraulic pump to perform overriding control of the hydraulic pump. The adjustable flow valve or fixed throttle orifice in the path can limit the flow rate through the sequence valve.

[0061] A closed-loop hydraulic drive circuit achieves the required speed and working pressure by matching the flow rates of a variable pump and a variable motor. Under normal circumstances, the hydraulic pump outputs flow to drive the motor and establishes a certain pressure between the hydraulic pump outlet and the motor inlet. The output flow rate of the hydraulic pump determines the motor speed. When the displacement of the hydraulic pump decreases rapidly while the hydraulic motor maintains its original speed, the output flow rate of the hydraulic pump will be less than the flow rate required for the hydraulic motor to maintain its speed, while the output flow rate of the hydraulic motor will be greater than the flow rate sucked in by the hydraulic pump. At this time, the hydraulic motor will operate as a pump, and the hydraulic pump will operate as a motor, with the hydraulic motor driving the hydraulic pump to rotate. Alternatively, when the displacement of the hydraulic pump remains constant and the speed of the hydraulic motor increases rapidly, the output flow rate of the hydraulic pump will also be less than the flow rate sucked in by the hydraulic motor, and the output flow rate of the hydraulic motor will be greater than the flow rate sucked in by the hydraulic pump. In this case, the hydraulic pump will operate as a motor, and the hydraulic motor will operate as a pump.

[0062] In some possible implementations, the control method of the multi-stage pressure overriding control valve group of the closed hydraulic system is characterized in that, under non-high-speed running conditions, the two-position three-way solenoid valve A2 or the two-position three-way solenoid valve B17 controls whether the input port and the subsequent channel are connected or disconnected through de-energization or energization logic. When the two-position three-way solenoid valve A2 is de-energized and the two-position four-way solenoid valve A3 is energized, or the two-position three-way solenoid valve B17 is de-energized and the two-position four-way solenoid valve B16 is energized, and the pressure at the inlet of the sequence valve B5 or the sequence valve D14 reaches its set opening pressure, the sequence valve B5 or the sequence valve D14 will be connected. The pressurized oil passes through the sequence valve B5 or the sequence valve D14 and the subsequent check valves A7 or B8 or C12 or D13 to reach the output ports X3A23, X3B25, X4A24, and X4B26, thereby entering the variable mechanism of the hydraulic pump to perform overriding control of the hydraulic pump.

[0063] The multi-stage pressure overriding control valve group of the closed hydraulic system described in this embodiment can detect pressure changes in the drive circuit of the high-speed travel system or the working system under different operating conditions, control the displacement of the hydraulic pump, limit the maximum reverse pressure of the high-speed travel drive system or the highest pressure of the working system, thereby effectively controlling the magnitude of the reverse drag force of the high-speed travel system on the engine and the highest pressure of the non-high-speed travel working system, ensuring the normal function of the engine and hydraulic drive circuit components and the operational safety of the entire vehicle.

[0064] In this embodiment, the reverse pressure control in high-speed travel conditions and the maximum pressure limiting process of the non-high-speed travel working system are hydraulically automatic controlled, which is rapid, sensitive and accurate.

[0065] The pressure settings of sequence valves A4, B5, C15, D14, and relief valve 6 mentioned above are all adjustable and can be set according to the actual requirements of the components selected in the system.

[0066] This application also provides a hydraulic system, including the above-described closed hydraulic system multi-stage pressure overriding control valve group.

[0067] This application also provides a road maintenance vehicle, including a frame and the aforementioned hydraulic system mounted on the frame. The hydraulic system and the road maintenance vehicle have the same technical effects as the aforementioned control valve assembly.

[0068] The foregoing disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described above. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0069] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0070] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A multi-stage pressure overriding control valve assembly for a closed hydraulic system, characterized in that, include: Valve body; The first branch assembly is disposed on the valve body. The first branch assembly is provided with an oil inlet MA, a throttle valve A, a two-position three-way solenoid valve A, a two-position four-way solenoid valve A, a first sequence valve group, a first check valve group, and an output oil port X3B and an output oil port X3A in sequence from upstream to downstream. The first sequence valve group includes a sequence valve A and a sequence valve B, and the first check valve group includes a check valve A and a check valve B. The sequence valve A is connected to the output oil ports X3A and X3B through the check valves A and B, and the sequence valve B is connected to the output oil ports X3A and X3B through the check valves A and B. The pressure of the sequence valves A and B is adjustable. The second branch assembly is disposed on the valve body. The second branch assembly is provided with an oil inlet MB, a throttle valve B, a two-position three-way solenoid valve B, a two-position four-way solenoid valve B, a second sequence valve group, a second check valve group, and an output oil port X4A and an output oil port X4B in sequence from upstream to downstream. The second sequence valve group includes a sequence valve C and a sequence valve D. The second check valve group includes a check valve D and a check valve C. The sequence valve C is connected to the output oil ports X4A and X4B through the check valves C and D. The sequence valve D is connected to the output oil ports X4A and X4B through the check valves C and D. The pressure of the sequence valves C and D is adjustable. Specifically, when the two-position four-way solenoid valve A is de-energized, the output port of the two-position three-way solenoid valve A is connected to the input port of the sequence valve A. When the two-position four-way solenoid valve B is de-energized, the output port of the two-position three-way solenoid valve B is connected to the input port of the sequence valve C. The set pressure of the sequence valves A and C is the maximum reverse hydraulic pressure under high-speed travel conditions. When the two-position four-way solenoid valve A is energized, the output port of the two-position three-way solenoid valve A is connected to the input port of the sequence valve B. When the two-position four-way solenoid valve B is energized, the output port of the two-position three-way solenoid valve B is connected to the input port of the sequence valve D. The set pressure of the sequence valves B and D is the maximum output pressure of the hydraulic pump under non-high-speed travel conditions.

2. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 1, characterized in that, A two-position two-way solenoid valve A is installed between the downstream output port X3A of check valve A and the downstream output port X4A of check valve C, and a two-position two-way solenoid valve B is installed between the downstream output port X3B of check valve B and the downstream output port X4B of check valve D. When the two-position two-way solenoid valve A is de-energized, the output port X3A and the output port X4A are connected. When the two-position two-way solenoid valve B is de-energized, the output port X3B and the output port X4B are connected.

3. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 1, characterized in that, Downstream of sequence valves A and B, as well as downstream of sequence valves C and D, are shuttle valves. Downstream of each shuttle valve is an overflow valve, the pressure of which is adjustable.

4. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 3, characterized in that, The overflow valve is also connected to the K3 pressure test port; The two-position four-way solenoid valve A is connected to the pressure measuring port K2; The two-position four-way solenoid valve B is connected to the pressure test port K1.

5. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 1, characterized in that, The throttle valve A is an adjustable throttle valve or a fixed throttle orifice.

6. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 1, characterized in that, The throttle valve B is an adjustable throttle valve or a fixed throttle orifice.

7. The multi-stage pressure overriding control valve assembly for a closed hydraulic system according to claim 1, characterized in that, The oil inlet MA and the oil inlet MB are respectively connected to the main oil inlet A and the main oil inlet B of the hydraulic system drive circuit.

8. A hydraulic system, characterized in that, include: The multi-stage pressure overriding control valve assembly of the closed hydraulic system according to any one of claims 1-7.

9. A road maintenance vehicle, characterized in that, include: The chassis and the hydraulic system of claim 8 mounted on the chassis.

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