Hydraulic drive system and engineering vehicle

Abstract

The application discloses a hydraulic driving system and an engineering vehicle, and relates to the field of engineering machinery, which is used for reducing the phenomenon that a diesel engine is overspeeded by back thrust. The hydraulic driving system comprises a motor, a hydraulic pump, a first check valve, a loading overflow valve and a pilot overflow valve. The motor comprises a first working oil port and a second working oil port. The hydraulic pump comprises a third working oil port and a fourth working oil port. The first check valve is arranged on an oil path between the second working oil port of the motor and the fourth working oil port of the hydraulic pump. The loading overflow valve is arranged in parallel with the first check valve and also arranged on the oil path between the second working oil port of the motor and the fourth working oil port of the hydraulic pump. The pilot overflow valve is communicated with a control oil port of the loading overflow valve to control the valve position of the loading overflow valve. The hydraulic driving system provided by the above technical scheme avoids the additional energy loss of the system caused by the excessively high loading pressure, so that the working efficiency of the system can be ensured while the equipment is full-speed operated in a passive state.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of construction machinery, in particular to a hydraulic drive system and a construction vehicle. BACKGROUND

[0002] Hydraulic drive system is widely used in various mobile construction machinery as a power system driving device. Diesel engine is the most widely used power source for mobile construction machinery hydraulic system. In terms of hydraulic system type, considering system efficiency and system economy, especially for high-power (high-flow) system, closed hydraulic system is relatively more common.

[0003] The energy feedback of closed hydraulic system under the condition of driving system doing negative work (such as lowering under load or downhill) is also a double-edged sword. As a common characteristic of itself, the diesel engine can withstand limited load reverse torque. Therefore, when the motor feedback energy to the power system without other pump consumption, the feedback torque of the system cannot exceed the diesel engine itself limit. If it exceeds the limit, the diesel engine will be reverse speeded up.

[0004] In the related art, for the problem of diesel engine being reverse speeded up in the closed hydraulic system, the common method is to keep the design of the commonly used closed hydraulic system without processing. SUMMARY

[0005] The present application provides a hydraulic drive system and a construction vehicle to reduce the phenomenon of diesel engine being reverse speeded up.

[0006] The present application provides a hydraulic drive system, comprising:

[0007] a motor, comprising a first working oil port and a second working oil port;

[0008] a hydraulic pump, comprising a third working oil port and a fourth working oil port;

[0009] a first check valve arranged on an oil path between the second working oil port of the motor and the fourth working oil port of the hydraulic pump;

[0010] a loading relief valve arranged in parallel with the first check valve and also arranged on the oil path between the second working oil port of the motor and the fourth working oil port of the hydraulic pump; and

[0011] a pilot relief valve in communication with a control oil port of the loading relief valve to control the valve position of the loading relief valve.

[0012] In some embodiments, the hydraulic drive system further comprises:

[0013] a diesel engine; the pilot relief valve takes the actual speed of the diesel engine as a control signal to change the valve position of the pilot relief valve.

[0014] In some embodiments, the oil inlet of the first check valve is in fluid communication with the second working oil port of the motor, the oil outlet of the first check valve is provided with a first spring, and the oil outlet of the first check valve is in fluid communication with the fourth working oil port of the hydraulic pump.

[0015] In some embodiments, the oil inlet of the loading relief valve is in fluid communication with the fourth working oil port of the hydraulic pump, the oil outlet of the loading relief valve is in fluid communication with the second working oil port of the motor, the first control end of the loading relief valve is in fluid communication with the oil inlet of the loading relief valve, the second control end of the loading relief valve is provided with a second spring, and the second control end of the loading relief valve is in fluid communication with the pilot relief valve.

[0016] In some embodiments, the control end of the pilot relief valve is provided with an actual rotating speed of the diesel engine as a control signal, the first oil port of the pilot relief valve is in fluid communication with the second control end of the loading relief valve, and the second oil port of the pilot relief valve is in fluid communication with an oil tank.

[0017] In some embodiments, the hydraulic driving system further comprises:

[0018] A second check valve is arranged at the second working oil port of the motor to realize one-way oil return.

[0019] In some embodiments, the oil inlet of the second check valve is in fluid communication with the oil supplementing oil path of the hydraulic pump.

[0020] In some embodiments, the hydraulic pump comprises:

[0021] A main pump comprises the third working oil port and the fourth working oil port, the third working oil port of the main pump is in fluid communication with the first working oil port of the motor, and the fourth working oil port of the main pump is in fluid communication with the oil inlet of the loading relief valve.

[0022] A supplementing pump is mechanically connected with the main pump, and the oil inlet of the second check valve is in fluid communication with the first oil outlet of the supplementing pump.

[0023] In some embodiments, the second oil outlet of the second check valve is in fluid communication with the second working oil port of the motor, and the second oil outlet of the second check valve is further provided with a third spring.

[0024] The embodiments of the present application also provide an engineering vehicle comprising the hydraulic driving system provided by any of the technical solutions of the present application.

[0025] The hydraulic driving system provided by the technical scheme has the advantages that the loading pressure can be controlled in time according to the load condition, the extra energy loss of the system caused by the excessively high loading pressure is avoided, the equipment can run at full speed in the passive state without reducing the displacement of the hydraulic pump, the diesel engine is protected, the system failure rate is reduced, the reliability of the system is improved, and the working efficiency of the system is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and serve to explain the principles of the application, and do not limit the application in any way. In the drawings:

[0027] Figure 1 The principle schematic view of the hydraulic driving system provided by the embodiment of the application.

[0028] Figure 2 The hydraulic oil flow direction schematic view of the active driving state of the hydraulic driving system provided by the embodiment of the application.

[0029] Figure 3 The hydraulic oil flow direction schematic view of the passive driving state of the hydraulic driving system provided by the embodiment of the application.

[0030] Reference signs:

[0031] 1, motor; 2, hydraulic pump; 3, first check valve; 4, loading relief valve; 5, pilot relief valve; 6, second check valve; 11, first working oil port; 12, second working oil port; 21, third working oil port; 22, fourth working oil port; 23, main pump; 24, oil supplement pump. DETAILED DESCRIPTION

[0032] The technical scheme provided by the application will be described in detail below. Figures 1-3 The technical scheme provided by the application will be described in detail below.

[0033] The inventor finds that the diesel engine reverse thrust overspeed problem in the related art is not treated because the feedback torque of the hydraulic system to the diesel engine is limited. The related art considers that even if the closed hydraulic system has high overall efficiency, the overall mechanical and hydraulic driving efficiency of the system only accounts for a certain ratio of the total driving power. Even in the maximum working power condition, when the driving system is "driven", with the "help" of the overall driving efficiency of the equipment, the diesel engine will not be overloaded by the reverse thrust. The inventor considers that this way artificially ignores the possibility of the diesel engine reverse thrust overspeed problem, and the system has potential risks. The technical scheme of the embodiment of the application directly faces this problem and provides a corresponding solution.

[0034] Reference is made to Figure 1The embodiment of the present application provides a hydraulic driving system, and the hydraulic driving system can be a closed hydraulic system.

[0035] The hydraulic driving system comprises a motor 1, a hydraulic pump 2, a first check valve 3, a load relief valve 4 and a pilot relief valve 5. The motor 1 comprises a first working oil port 11 and a second working oil port 12. The hydraulic pump 2 comprises a third working oil port 21 and a fourth working oil port 22. The first check valve 3 is arranged on an oil circuit between the second working oil port 12 of the motor 1 and the fourth working oil port 22 of the hydraulic pump 2. The load relief valve 4 is arranged in parallel with the first check valve 3 and also on the oil circuit between the second working oil port 12 of the motor 1 and the fourth working oil port 22 of the hydraulic pump 2. The pilot relief valve 5 is in communication with a control oil port of the load relief valve 4, so as to control the valve position of the load relief valve 4.

[0036] The hydraulic system is a system for converting mechanical energy into hydraulic energy by the hydraulic pump 2 to drive an executing element (the hydraulic motor 1 or the oil cylinder).

[0037] The closed hydraulic system is an internal circulation hydraulic driving system for directly controlling the hydraulic motor 1 by the hydraulic pump 2. The closed system directly controls the action speed and direction by controlling the displacement of the main pump 23 of the hydraulic pump 2. The motor 1 and the hydraulic pump 2 are directly connected through a pipeline, and compared with the open system, the closed system has no additional pressure loss caused by the reversing valve, and the overall efficiency of the hydraulic system is more advantageous. The closed system controls the load lowering process by the circuit formed by the hydraulic pump 2 and the motor 1, avoids the additional system heat loss caused by the open valve control, and the stability of the closed system in the load lowering process is relatively better, especially for the high-power system, there is no size and flow limitation problem of the control hydraulic valve. In the load lowering process of the closed system control, the gravitational potential energy of the load can be finally recycled as energy feedback and converted into mechanical energy by the main pump 23. In the case of compound action, the closed system can be used to drive other motors working synchronously.

[0038] The first working oil port 11 and the second working oil port 12 of the motor 1 are respectively connected to different control valves, so as to realize the action of the executing mechanism.

[0039] Referring to Figure 1 The hydraulic pump 2 comprises a main pump 23 and a supplement pump 24, and the two are fixedly connected in a mechanical mode. The main pump 23 comprises the third working oil port 21 and the fourth working oil port 22; the third working oil port 21 of the main pump 23 is in fluid communication with the first working oil port 11 of the motor 1. The supplement pump 24 is mechanically connected with the main pump 23; the oil inlet of the second check valve 6 is in fluid communication with the first oil outlet 241 of the supplement pump 24.

[0040] The main pump 23 provides hydraulic oil and provides the hydraulic oil to the required valve group. The hydraulic oil provided by the main pump 23 also flows to the first working oil port 11 of the motor 1 through the third working oil port 21.

[0041] In some embodiments, the hydraulic drive system further comprises a diesel engine. The pilot relief valve 5 takes the actual speed of the diesel engine as a control signal, and controls the pilot pressure setting of the pilot relief valve 5 by adjusting the size of the control signal of the pilot relief valve 5.

[0042] The system's counter-thrust torque of the diesel engine = the feedback torque of the main pump 23 of the hydraulic pump 2 - the driving torque of the oil supplement pump 24 = the displacement of the main pump 23 * the A&B pressure difference of the main pump 23 * n - the driving torque of the oil supplement pump 24, wherein n is a fixed coefficient. The A&B pressure difference of the main pump 23 refers to the pressure difference between the third working oil port 21 and the fourth working oil port 22 of the main pump 23. The A&B pressure difference of the main pump 23 is determined by the load and is proportional to the load.

[0043] The above technical solution can limit the torque of the hydraulic pump 2 (i.e. the pressure difference between the third working oil port 21 and the fourth working oil port 22) by adding a certain loading pressure on the low-pressure side of the hydraulic pump 2. In any working condition, the relationship between the load pressure, the A&B pressure difference of the hydraulic pump 2 and the loading pressure always satisfies the following relationship: the load pressure of the hydraulic drive system = the pressure difference between the third hydraulic oil port and the fourth hydraulic oil port of the hydraulic pump 2 + the loading pressure + the system oil supplement pressure. The above technical solution can keep the system working efficiently without reducing the displacement of the hydraulic pump 2, and realizes the control of the pressure difference between the third working oil port 21 and the fourth working oil port 22 of the hydraulic pump 2.

[0044] In some embodiments, the oil inlet 30 of the first check valve 3 is in fluid communication with the second working oil port 12 of the motor 1, the oil outlet 32 of the first check valve 3 is provided with the first spring 31, and the oil outlet 32 of the first check valve 3 is in fluid communication with the fourth working oil port 22 of the hydraulic pump 2.

[0045] In some embodiments, the oil inlet 42 of the loading relief valve 4 is in fluid communication with the fourth working oil port 22 of the hydraulic pump 2, the oil outlet 41 of the loading relief valve 4 is in fluid communication with the second working oil port 12 of the motor 1, the first control end of the loading relief valve 4 is in fluid communication with the oil inlet 42 of the loading relief valve 4, and the second control end of the loading relief valve 4 is provided with the second spring 43 and is in fluid communication with the pilot relief valve 5. The load lowering stability is mainly controlled by the loading relief valve 4, and such arrangement has higher running stability for a large-flow system.

[0046] Referring to Figure 1 , the pilot relief valve 5 is specifically a pilot proportional relief valve. In some embodiments, the control end of the pilot relief valve 5 takes the actual speed of the diesel engine as a control signal, the first oil port 51 of the pilot relief valve 5 is in fluid communication with the second control end of the loading relief valve 4, and the second oil port 52 of the pilot relief valve 5 is in fluid communication with the oil tank.

[0047] The technical scheme increases the loading overflow valve 4 and the pilot overflow valve 5 at the outlet of the hydraulic pump 2. The diesel engine rotating speed is taken as the feedback signal, and the pressure value of the loading overflow valve 4 is adjusted by controlling the pilot overflow valve 5.

[0048] In some embodiments, the hydraulic driving system further comprises a second one-way valve 6 arranged at the second working oil port 12 of the motor 1 to realize one-way oil return. The oil inlet of the second one-way valve 6 is in fluid communication with the first oil outlet 241 of the oil supplement pump 24.

[0049] When the pressure at the A port and the B port (the third working oil port 21 and the fourth working oil port 22) of the hydraulic pump 2 exceeds the system oil supplement pressure after loading, the oil supplement pump 24 supplements oil for the system through the second one-way valve 6.

[0050] In some embodiments, the second oil outlet 61 of the second one-way valve 6 is in fluid communication with the second working oil port 12 of the motor 1, and the third spring 62 is further installed at the second oil outlet 61 of the second one-way valve 6.

[0051] In some embodiments, the oil inlet 63 of the second one-way valve 6 is in fluid communication with the oil supplement oil path of the hydraulic pump 2.

[0052] In the driven state, when the feedback torque of the diesel engine (the pressure difference between the third working oil port 21 and the fourth working oil port 22 of the hydraulic pump 2) exceeds the limited value, the diesel engine will be over-speeded by back thrust. The rotating speed signal of the diesel engine is fed back to the pilot overflow valve 5, and the pressure of the loading overflow valve 4 is timely controlled, so that the reaction torque value of the diesel engine can be limited and adjusted at all times.

[0053] Referring to Figure 1 , the pipeline between the A port (the third working oil port 21) of the hydraulic pump 2 and the A port (the first working oil port 11) of the motor 1 generates a pressure area for the load, and the hydraulic pump 2 and the motor 1 convert mechanical energy and hydraulic energy to each other to form high pressure in the pipeline area, and the torque generated by the motor 1 is used to control the load.

[0054] The pipeline area between the B port (the second working oil port 12) of the hydraulic pump 2 and the loading overflow valve 4 is a loading pressure area.

[0055] The pipeline area communicated with the B port (the second working oil port 12) of the motor 1 is a system oil supplement pressure area, and this part always works under the system oil supplement pressure.

[0056] The working principle of the hydraulic driving system will be introduced below.

[0057] Referring to Figure 2 , the hydraulic system is in the active driving state (load lifting), and the system forms a loop through the first one-way valve 3. The oil flow direction is shown in Figure 2As shown, the oil flows from the third working oil port 21 of the hydraulic pump 2 to the first working oil port of the motor. Then the hydraulic oil flows out of the second working oil port 12 of the motor 1, passes through the first check valve 3 to the fourth working oil port 22 of the hydraulic pump 2.

[0058] Referring to Figure 3 When the system is in the driven state (under load), the system forms a loop through the loading relief valve 4. The hydraulic oil flows from the fourth working oil port 22 of the hydraulic pump 2 to the loading relief valve 4, then enters the motor 1 through the second working oil port 12 of the motor 1, then flows out of the first working oil port 11 of the motor 1, and finally flows back to the third working oil port 21 of the hydraulic pump 2. When the load feedback exceeds the diesel engine self-limitation, the diesel engine speed increases, and the actual speed is used to feedback control the pilot relief valve 5. The pressure of the loading relief valve 4 is controlled through the pilot relief valve 5, thereby reducing the pressure difference between the hydraulic pump 2A, B ports (the third working oil port 21 and the fourth working oil port 22), and reducing the feedback torque of the system to the diesel engine. In this process, the load can be kept at high speed.

[0059] The technical scheme of the embodiment of the present application adds the first check valve 3, the loading relief valve 4 and the pilot relief valve 5 for the state of the hydraulic motor 1 being driven in one direction. For the state of being driven in two directions such as walking uphill and downhill, the first check valve 3, the loading relief valve 4 and the pilot relief valve 5 can be added to both ends of the hydraulic pump 2. In this case, the working principle of the system is the same as that of the one-way system.

[0060] The embodiment of the present application also provides an engineering vehicle comprising the hydraulic drive system provided by any of the technical schemes of the present application.

[0061] The above technical scheme can be applied to a closed hydraulic system driven by a diesel engine, used for passive overload protection of the engine, and has higher reliability and safety, simple operation, and meets the development trend of intelligence, economy, efficiency and safety. The comprehensive efficiency of the hydraulic system is considered while the diesel engine is effectively protected, and the purpose of energy saving is achieved.

[0062] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the protection scope of the present application.

[0063] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some of the technical features can be replaced by equivalents, but these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A hydraulic drive system, characterized in that, include: The motor (1) includes a first working oil port (11) and a second working oil port (12); The hydraulic pump (2) includes a third working port (21) and a fourth working port (22); The first check valve (3) is arranged in the oil line between the second working oil port (12) of the motor (1) and the fourth working oil port (22) of the hydraulic pump (2); A relief valve (4) is arranged in parallel with the first check valve (3) and is also arranged in the oil line between the second working port (12) of the motor (1) and the fourth working port (22) of the hydraulic pump (2); and The pilot relief valve (5) is connected to the oil control port of the loading relief valve (4) to control the valve position of the loading relief valve (4); The oil inlet (30) of the first check valve (3) is in fluid communication with the second working oil port (12) of the motor (1), the oil outlet (32) of the first check valve (3) is equipped with a first spring (31), and the oil outlet (32) of the first check valve (3) is in fluid communication with the fourth working oil port (22) of the hydraulic pump (2). The inlet (42) of the loading relief valve (4) is fluidly connected to the fourth working port (22) of the hydraulic pump (2), and the outlet (41) of the loading relief valve (4) is fluidly connected to the second working port (12) of the motor (1); the first control end of the loading relief valve (4) is fluidly connected to the inlet (42) of the loading relief valve (4); the second control end of the loading relief valve (4) is provided with a second spring (43), and the second control end of the loading relief valve (4) is fluidly connected to the pilot relief valve (5).

2. The hydraulic drive system according to claim 1, characterized in that, Also includes: diesel engine; The pilot relief valve (5) uses the actual speed of the diesel engine as a control signal to change the valve position of the pilot relief valve (5).

3. The hydraulic drive system according to claim 1, characterized in that, The control terminal of the pilot relief valve (5) uses the actual speed of the diesel engine as the control signal. The first oil port (51) of the pilot relief valve (5) is fluidly connected to the second control terminal of the loading relief valve (4), and the second oil port (52) of the pilot relief valve (5) is fluidly connected to the oil tank.

4. The hydraulic drive system according to claim 1, characterized in that, Also includes: The second check valve (6) is arranged at the second working oil port (12) of the motor (1) to realize one-way oil return.

5. The hydraulic drive system according to claim 4, characterized in that, The oil inlet of the second check valve (6) is in fluid communication with the oil replenishment circuit of the hydraulic pump (2).

6. The hydraulic drive system according to claim 4, characterized in that, The hydraulic pump (2) includes: The main pump (23) includes the third working port (21) and the fourth working port (22); the third working port (21) of the main pump (23) is in fluid communication with the first working port (11) of the motor (1); and The replenishing pump (24) is mechanically connected to the main pump (23); the oil inlet (63) of the second check valve (6) is in fluid communication with the first oil outlet (241) of the replenishing pump (24).

7. The hydraulic drive system according to claim 4, characterized in that, The second oil outlet (61) of the second check valve (6) is in fluid communication with the second working oil port (12) of the motor (1), and a third spring (62) is also installed on the second oil outlet (61) of the second check valve (6).

8. An engineering vehicle, characterized in that, Includes the hydraulic drive system described in any one of claims 1 to 7.

Images