Oil changing device and method for relieving pressure impact of closed hydraulic system pipeline

Abstract

The application discloses a kind of oil change device and relieving method that can relieve pressure impact of closed hydraulic system pipeline, the closed hydraulic system is one-way operation closed hydraulic system, the oil change device includes oil change valve, and shuttle valve (1) is arranged in oil change valve, first oil inlet (10), second oil inlet (11) and oil outlet (12) are arranged on shuttle valve (1), first oil inlet (10) is connected with the outlet oil path A of system, second oil inlet (11) is connected with the inlet oil path B of system, and oil outlet (12) is connected with oil tank T by low pressure overflow valve (2), further include check valve (3), the oil outlet end of check valve (3) is connected with first oil inlet (10), and the oil inlet end of check valve (3) is connected with second oil inlet (11).The application is used in one-way operation closed hydraulic system, has the advantages that system pipeline pressure pulsation can be avoided and equipment can be slowed down to stop down, and hydraulic pump can be avoided to lock and fail.

Description

Technical Field

[0001] This invention belongs to the field of closed hydraulic systems, and particularly relates to an oil change device and method for mitigating pressure shocks in closed hydraulic system pipelines. Background Technology

[0002] Unidirectional closed-loop hydraulic systems (such as fan-cooled systems) are common hydraulic systems in engineering machinery and weaponry. Compared with ordinary open-loop hydraulic systems, closed-loop hydraulic systems not only have lower energy consumption in their circuits, but also have a more compact structure. Their functions, such as oil pump for oil change, oil replenishment, system overflow, and control, are all integrated into the hydraulic pump, which simplifies pipeline connections. This not only reduces leakage and pipeline vibration caused by pipeline connections and improves system reliability, but also simplifies the operation process. However, because the hydraulic oil in a closed system is always in a closed circulation state, heat dissipation is very difficult, and it is also difficult to remove metal debris and impurities from the hydraulic system. Therefore, a change valve is usually connected in parallel on the hydraulic pump or system pipeline. The change valve is equipped with a shuttle valve. The two inlets of the shuttle valve introduce hydraulic fluid into the system's inlet and outlet oil circuits, respectively. High-pressure oil pushes the shuttle valve to move, introducing low-pressure oil into the return oil circuit. A low-pressure relief valve is connected in series on the return oil circuit. The size of the throttle orifice on the low-pressure relief valve can be used to return a relatively fixed flow of change oil to the oil tank. After filtration and cooling, it is then returned to the hydraulic system by the replenishment pump. The hydraulic structure of the change valve is as follows: Figure 4 As shown.

[0003] In existing closed-loop hydraulic systems, the set pressure of the high-pressure relief valve integrated on the hydraulic pump is typically 35 MPa, and in some high-pressure systems it even reaches over 45 MPa. This high set pressure of the relief valve allows the hydraulic pump to provide more torque output. The acceleration and deceleration of the hydraulic pump in a closed-loop system are mainly achieved by changing its speed or displacement. During the deceleration process of the hydraulic pump, energy unloading is integrated into the high-pressure relief valve. The high set pressure of the relief valve can provide a large reverse torque to the hydraulic pump and interact with the inertial torque of the equipment, helping the equipment to brake and stop smoothly. However, this also brings another problem. For some small-weight, high-speed equipment, when it decelerates, the torque generated by the inertial load is too small to overcome the reverse torque generated by the hydraulic pump driven by the high-pressure relief valve at its high set pressure. The high-pressure relief valve opens for a short time or fails to open, resulting in large pressure pulsations in the system pipeline and insufficient sliding distance or even sudden stop of the entire equipment, posing safety hazards to equipment operation and system stability. For some equipment with low structural strength, such as fans in a fan cooling system, sudden deceleration or impact can affect structural strength, severely reduce service life, and may even lead to disintegration, posing safety hazards to production. Furthermore, when the equipment stops suddenly at high speed, the inertial load drives the hydraulic pump to rotate, causing the hydraulic pump to suck in air, which may lead to the hydraulic pump seizing and permanent failure.

[0004] In summary, existing unidirectional closed-loop hydraulic systems have the drawback that when the equipment decelerates or the hydraulic pump stops at high speed, but the equipment's inertial torque is insufficient to overcome the reverse torque generated by the hydraulic pump under high pressure, it may cause severe pipeline pressure pulsation and force the equipment to stop suddenly. Furthermore, the hydraulic pump may seize up or even fail permanently. Summary of the Invention

[0005] The purpose of this invention is to provide an oil change device and method for mitigating pressure shocks in closed-loop hydraulic systems. This invention is used in unidirectional closed-loop hydraulic systems and has the advantages of preventing system pipeline pressure pulsations and allowing equipment to stop slowly, while also preventing hydraulic pump seizure and failure.

[0006] The technical solution of the present invention is an oil changing device that can alleviate pressure shock in the pipeline of a closed hydraulic system. The closed hydraulic system is a one-way operating closed hydraulic system. The oil changing device includes an oil changing valve, which is equipped with a shuttle valve. The shuttle valve is equipped with a first oil inlet, a second oil inlet, and an oil outlet. The first oil inlet is connected to the system's outlet oil circuit A, the second oil inlet is connected to the system's inlet oil circuit B, and the oil outlet is connected to the oil tank T through a low-pressure relief valve. It also includes a check valve. The oil outlet end of the check valve is connected to the first oil inlet, and the oil inlet end of the check valve is connected to the second oil inlet. The check valve is equipped with a spring that determines the opening pressure of the check valve.

[0007] In the aforementioned oil changing device that can alleviate pressure shock in closed hydraulic system pipelines, the shuttle valve housing is provided with a first cavity and a second cavity, a through hole is provided between the first cavity and the second cavity, the middle part of the through hole is connected to the oil tank T, the first cavity is connected to the first oil inlet, and the second cavity is connected to the second oil inlet.

[0008] The one-way valve includes a valve core located in the first cavity, one end of which is sealed at the end of the through hole, and the other end of which is provided with a spring.

[0009] In the aforementioned oil change device that can alleviate pressure shock in closed hydraulic system pipelines, the valve core and the end face conical surface of the through hole are in contact.

[0010] In the aforementioned oil change device that can alleviate pressure shock in closed hydraulic system pipelines, the outer end of the valve core is provided with a screw plug connected to the housing, the inner end of the screw plug is provided with a guide hole that is slidably connected to the valve core, and the spring is disposed in the guide hole.

[0011] In the aforementioned oil change device that can alleviate pressure shock in closed hydraulic system pipelines, the outer end of the valve core is provided with a blind hole into which a spring extends.

[0012] A method for mitigating pressure shock in a closed hydraulic system is provided, wherein the closed hydraulic system employs an oil changing device according to any one of claims 1 to 5, and the opening pressure of the check valve is changed by adjusting the preload of the spring to enable smooth braking of the equipment.

[0013] In the aforementioned method for mitigating pressure shock in closed hydraulic system pipelines, the preload of the spring is adjusted according to the inertial torque of the equipment driven by the closed hydraulic system, thereby changing the opening pressure of the check valve and enabling the equipment to brake smoothly.

[0014] Compared to existing technologies, this invention incorporates a check valve into the existing oil change valve. When the equipment is about to undergo high-speed deceleration or the hydraulic pump is about to stop at high speed, the check valve creates a stable pressure difference between the inlet and outlet oil lines of the system. This pressure difference generates a stable reverse braking torque in the hydraulic pump, which, combined with the equipment's original inertial torque, ensures that the high-pressure relief valve has a longer opening time, reducing system pipeline pressure pulsation and allowing the equipment to coast for a longer period before stopping slowly, thus avoiding safety hazards to system stability and equipment operation. For equipment with lower structural strength, the slow stopping reduces impact, increases service life, and lowers the risk of disintegration, reducing production safety hazards. Furthermore, because the equipment stops smoothly, the replenishing pump also stops smoothly, preventing the hydraulic pump from dry-suction and avoiding hydraulic pump seizure and failure. Therefore, this invention, used in unidirectional closed-loop hydraulic systems, has the advantages of avoiding system pipeline pressure pulsation and enabling slow equipment stopping, while also preventing hydraulic pump seizure and failure. Attached Figure Description

[0015] Figure 1 This is a hydraulic schematic diagram of the present invention.

[0016] Figure 2 This is a cross-sectional view of the present invention.

[0017] Figure 3 This is a structural diagram of a one-way valve.

[0018] Figure 4 This is the hydraulic schematic diagram of an existing oil change valve.

[0019] The markings in the attached diagram are as follows: 1-Shuttle valve, 10-First oil inlet, 11-Second oil inlet, 12-Oil outlet, 13-Housing shell, 14-First cavity, 15-Second cavity, 16-Through hole; 2-Low-pressure relief valve; 3-Check valve, 30-Spring, 31-Valve core, 32-Plug, 33-Guide hole, 34-Blind hole, 35-Guide rod, 36-Plug. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0021] Example. An oil changing device that can alleviate pressure shocks in closed-loop hydraulic system pipelines, such as... Figure 1 As shown, the closed-loop hydraulic system is a unidirectional closed-loop hydraulic system. The oil changing device includes an existing oil changing valve, which contains a shuttle valve 1. The shuttle valve 1 has a first oil inlet 10, a second oil inlet 11, and an oil outlet 12. The first oil inlet 10 is connected to the system's outlet oil circuit A. Figure 1 As shown in Figure A), the second oil inlet 11 connects to the system's inlet oil circuit B. Figure 1 As shown in Figure B), the oil outlet 12 is connected to the oil tank T via the low-pressure overflow valve 2. Figure 1 As shown in Figure T), its characteristics are as follows:

[0022] It also includes a one-way valve 3, the oil outlet of which is connected to the first oil inlet 10, and the oil inlet of which is connected to the second oil inlet 11.

[0023] like Figure 2 As shown, the housing 13 of the shuttle valve 1 is provided with a first cavity 14 and a second cavity 15. A through hole 16 is provided between the first cavity 14 and the second cavity 15. The middle part of the through hole 16 is connected to the oil tank T. The first cavity 14 is connected to the first oil inlet 10, and the second cavity 15 is connected to the second oil inlet 11.

[0024] like Figure 3 As shown, the one-way valve 3 includes a valve core 31 located in the first cavity 14. The valve core 31 includes a guide rod 35 and a plug 36. The plug 36 is sealed at the end of the through hole 16. The outer end of the guide rod 35 is provided with a spring 30 that determines the opening pressure of the one-way valve 3.

[0025] The end face conical surfaces of the plug 36 and the through hole 16 are in contact.

[0026] The outer end of the guide rod 35 is provided with a screw plug 32 that is connected to the housing 13, and the inner end of the screw plug 32 is provided with a guide hole 33 that is slidably connected to the guide rod 35. The spring 30 is disposed in the guide hole 33.

[0027] The outer end of the guide rod 35 is provided with a blind hole 34 into which the spring 30 extends. The function of the blind hole 34 is to extend the length of the spring 30 while ensuring that the length of the one-way valve 3 remains unchanged, thus leaving a larger range for adjusting the preload of the spring 30.

[0028] Working principle: Figure 1As explained, this invention incorporates a one-way valve 3 into the existing oil change valve. When the hydraulic pump displacement or speed increases, the flow rate and pressure of the system's outlet oil circuit A increase. Since the pressure of outlet oil circuit A is higher than that of inlet oil circuit B, shuttle valve 1 moves upward, introducing the oil from inlet oil circuit B into the inlet of low-pressure relief valve 2. The low-pressure oil from inlet oil circuit B reaches the oil tank T through low-pressure relief valve 2, thus changing the oil in the system and achieving system cooling and oil cleaning. Simultaneously, high-pressure oil from outlet oil circuit A enters the outlet of check valve 3. The pressure difference between outlet oil circuit A and inlet oil circuit B, along with the elastic force generated by check valve spring 6, causes check valve 3 to close, and the system operates normally. When the hydraulic pump displacement decreases or the speed decreases, the flow rate and pressure of outlet oil circuit A decrease. Under the action of the inertial force of the drive device, the pressure of inlet oil circuit B is higher than that of outlet oil circuit A. When the pressure difference between inlet oil circuit B and outlet oil circuit A is greater than the opening pressure of check valve 3 (the opening pressure of check valve 3 is determined by the preload of spring 30 and the working area of ​​the oil pressure on plug 32), check valve 3 opens, the oil in inlet oil circuit B is depressurized, and the pressure difference between inlet oil circuit B and outlet oil circuit A is maintained at the set pressure of check valve 3. This pressure causes the hydraulic pump to generate a stable reverse braking torque. Under the same load, different set pressures of check valve 3 result in different equipment gliding times. The higher the opening pressure of check valve 3, the shorter the working time of the hydraulic pump; the lower the opening pressure of check valve 3, the longer the working time of the hydraulic pump.

[0029] A method for mitigating pressure shock in closed-loop hydraulic systems is provided. The closed-loop hydraulic system employs the aforementioned oil changing device. Based on the inertial torque of the equipment driven by the closed-loop hydraulic system (determined by variables such as the equipment's mass, volume, and structural strength, which are generally calculated or tested by engineers), the preload of spring 30 is adjusted to change the opening pressure of check valve 3, thus ensuring smooth braking of the equipment. Adjusting the preload of spring 30 only requires changing the screw depth of plug 32.

Claims

1. An oil changing device for relieving pressure shock in a closed hydraulic system, wherein the closed hydraulic system is a unidirectional closed hydraulic system, the oil changing device includes an oil changing valve, the oil changing valve is provided with a shuttle valve (1), the shuttle valve (1) is provided with a first oil inlet (10), a second oil inlet (11) and an oil outlet (12), the first oil inlet (10) is connected to the system's outlet oil circuit A, the second oil inlet (11) is connected to the system's inlet oil circuit B, and the oil outlet (12) is connected to the oil tank T through a low-pressure relief valve (2), characterized in that: It also includes a check valve (3), the oil outlet of the check valve (3) is connected to the first oil inlet (10), the oil inlet of the check valve (3) is connected to the second oil inlet (11), and the check valve (3) is provided with a spring (30) that determines the opening pressure of the check valve (3). The shuttle valve housing (13) is provided with a first cavity (14) and a second cavity (15). A through hole (16) is provided between the first cavity (14) and the second cavity (15). The middle part of the through hole (16) is connected to the oil tank T. The first cavity (14) is connected to the first oil inlet (10), and the second cavity (15) is connected to the second oil inlet (11). The one-way valve includes a valve core (31) located in the first cavity (14), one end of the valve core (31) is sealed at the end of the through hole (16), and the other end of the valve core (31) is provided with a spring (30).

2. The oil changing device for mitigating pressure shock in closed-loop hydraulic systems according to claim 1, characterized in that: The valve core (31) and the through hole (16) are connected by tapered surfaces.

3. The oil changing device for mitigating pressure shock in closed-loop hydraulic systems according to claim 1, characterized in that: The outer end of the valve core (31) is provided with a screw plug (32) connected to the housing (13), and the inner end of the screw plug (32) is provided with a guide hole (33) that is slidably connected to the valve core (31). The spring (30) is located in the guide hole (33).

4. The oil changing device for mitigating pressure shock in closed-loop hydraulic systems according to claim 3, characterized in that: The outer end of the valve core (31) is provided with a blind hole (34) into which the spring (30) extends.

5. A method for mitigating pressure shock in closed-loop hydraulic systems, characterized in that: The closed hydraulic system employs an oil changing device according to any one of claims 1 to 4, which changes the opening pressure of the check valve (3) by adjusting the preload of the spring (30) to make the equipment brake smoothly.

6. The method for mitigating pressure shock in closed-loop hydraulic systems according to claim 5, characterized in that: Based on the inertial torque of the equipment driven by the closed hydraulic system, the preload of the spring (30) is adjusted to change the opening pressure of the check valve (3) so that the equipment can brake smoothly.

Images