Multifunctional valve for closed hydraulic plunger variable pump and its use method

Abstract

The present invention discloses a multifunctional valve for a closed hydraulic plunger variable displacement pump and a method for use thereof. The multifunctional valve comprises a first valve sleeve, one end of which is provided with a hole A, a side wall of which is provided with a hole B, and the other end of which is provided with a threaded sleeve, the side wall of which is provided with a hole C. The first valve sleeve is provided within a second valve sleeve, and the second valve sleeve is provided within a first valve core. One end of the first valve core extends out of the second valve sleeve and abuts against the hole A. A first spring seat, a second spring seat, and a pressure-adjusting screw are sequentially provided on one side of the first valve core. A first spring is provided between the first valve core and the first spring seat, and a second spring is provided between the second spring seat and the pressure-adjusting screw. The first valve core is provided with a first through-hole, through which the hole A communicates with the inner cavity of the first valve sleeve. A guide hole is provided on the end surface of the first spring seat away from the hole A, and the second valve core is provided within the guide hole. One end of the second valve core is provided with a conical portion. The present invention has the advantages of reducing the processing cost of the variable displacement pump end cover and being relatively low in cost.

Description

Technical Field

[0001] The invention belongs to the field of closed hydraulic plunger variable pumps, and in particular relates to a multifunctional valve for a closed hydraulic plunger variable pump and a use method thereof. Background Art

[0002] Closed-loop hydraulic piston variable pumps are widely used in construction machinery such as truck cranes, crawler cranes, road rollers, and aerial work platforms. Compared to open-loop hydraulic systems, closed-loop hydraulic systems, consisting of a closed-loop hydraulic piston variable pump, hydraulic motor, and cylinder, simplify piping connections. This not only significantly saves installation space but also reduces problems such as leakage and vibration caused by piping connections, thereby improving system reliability. Closed-loop hydraulic systems reduce the chance of air entering the oil, ensuring smoother operation of the entire hydraulic system. Furthermore, closed-loop hydraulic piston variable pumps can directly control the flow direction of the output oil, ensuring smooth transitions and avoiding the hydraulic shock caused by various valves in open-loop systems. Consequently, closed-loop hydraulic piston variable pumps are gaining popularity with a growing number of mainframes.

[0003] Closed hydraulic systems constantly experience oil losses during operation (oil losses caused by the closed hydraulic plunger variable pump's own volumetric efficiency, leakage from actuators, leakage from pipelines, leakage from valves in the closed hydraulic system, etc.). To compensate for the oil losses in the closed hydraulic system and ensure the normal operation of the entire closed hydraulic system, a small-displacement fixed-flow pump, called a charge pump, is usually integrated into the closed hydraulic plunger variable pump. The charge pump has a small displacement and low pressure, and the outlet pressure of the charge pump is limited by a built-in charge relief valve. The closed hydraulic plunger variable pump has two independent outlets, A / B, which can both serve as high-pressure and low-pressure oil ports. The A / B ports are isolated by two one-way valves and connected by two relief valves. The charge pump replenishes the oil lost in the closed hydraulic system to the low-pressure side of the A / B port through the one-way valve. The charge pump always communicates with the low-pressure side of the A / B port. The two relief valves at ports A / B limit the maximum pressure of their respective oil ports to prevent overload of the closed hydraulic system. When the pressure of the closed hydraulic system is lower than the opening pressure set by the two relief valves, ports A / B are cut off; when the pressure of the closed hydraulic system is higher than the opening pressure set by the two relief valves, the relief valve on the high-pressure side of ports A / B opens to connect ports A / B.

[0004] Relief valves are divided into pilot-operated relief valves and direct-acting relief valves. The basic principle of a relief valve is to adjust the pressure through the negative feedback effect formed by the balance and movement of the valve core.

[0005] The working principle of a pilot-operated relief valve is as follows: when pressurized oil flows into the inlet, it acts on the lower end face of the main valve core. The valve body is designed with a damping orifice, allowing the pressurized oil to pass through the orifice and enter the right chamber of the pilot valve, ultimately acting on the pilot relief valve core. The pilot relief valve core is normally closed due to spring force. The spring's pre-set pressure can be adjusted using an external adjustment handle. When the hydraulic pressure is less than the spring's pre-set pressure, the pilot valve core remains closed, and the main valve core does not move accordingly. When the system pressure rises, the hydraulic pressure inside the pilot valve exceeds the spring's pre-set pressure, causing the pilot valve to open. The pressure drop across the damping orifice creates a pressure differential between the upper and lower ends of the main valve core, causing it to lift. This connects the previously sealed inlet and outlet oil paths, allowing pressurized oil to flow directly from the inlet to the outlet, achieving unloading.

[0006] The working principle of a direct-acting relief valve is as follows: When the direct-acting relief valve is connected to the system, hydraulic oil acts on the valve core, generating a force opposite to the spring's pre-set pressure. When the inlet pressure is lower than the relief valve's set pressure, the valve core does not open. The inlet pressure is primarily determined by the external load. When the oil force exceeds the spring's pre-set pressure, the valve core opens, and oil flows back to the tank through the relief port. The spring force increases as the relief valve opening increases until it balances the hydraulic force. When the relief valve begins to overflow, the pressure at the inlet remains essentially stable at the set value, providing a pressure-stabilizing function. The pressure-regulating screw adjusts the spring's pre-compression to adjust the relief valve's relief pressure.

[0007] The shut-off valve regulates the pump's displacement to ensure that the pump's operating pressure does not exceed the set shut-off pressure. When the pump's operating pressure exceeds the set pressure, the shut-off valve spool opens, allowing the control oil to the variable cylinder to return to the oil return position, returning the swash plate to zero, and maintaining the pump's zero displacement. Installing a shut-off valve on a closed-circuit pump prevents damage to the closed system due to excessive system pressure, thereby protecting the system.

[0008] Based on the working principle of a closed-loop variable displacement piston pump, it typically lacks oil replenishment, overflow, or shutoff functions. Therefore, control valves such as a replenishment valve, shutoff valve, and relief valve must be integrated. This results in multiple crossover oil circuits on the end cover of the closed-loop variable displacement piston pump, making oil circuit layout and processing difficult and costly. If a host system malfunctions, the entire host will be unable to move, and a bypass valve must usually be integrated into the pump. By adjusting the bypass valve plug, the swash plate is pushed back to zero, enabling short-distance movement of the host. The installation of the bypass valve further complicates oil circuit layout and processing, driving up processing costs.

[0009] Currently, the shut-off valves and relief valves used in closed-loop hydraulic plunger variable pumps on the market are relatively complex in structure, requiring high requirements for the clearance, coaxiality, and roughness between the valve core and the valve sleeve. These valves are difficult to process, especially the valve core step, which requires high machining accuracy (high requirements for valve sleeve coaxiality and coaxiality and roughness of the valve core and valve sleeve step). Otherwise, the valve core will be subjected to the hydraulic clamping force, causing the valve core to stagnate or even become stuck, resulting in poor opening performance of the shut-off valve and relief valve, and even damage to the pump. High-precision shut-off valves and relief valves also increase their cost. Summary of the Invention

[0010] The object of the present invention is to provide a multifunctional valve for a closed hydraulic plunger variable displacement pump and a method for using the same. The present invention has the advantages of reducing the processing cost of the variable displacement pump end cover and having a low cost itself.

[0011] The technical solution of the present invention is as follows: a multifunctional valve for a closed hydraulic plunger variable displacement pump comprises a first valve sleeve, one end of the first valve sleeve is provided with a hole A, a side wall of the first valve sleeve is provided with a hole B, the other end of the first valve sleeve is provided with a screw sleeve, and a side wall of the screw sleeve is provided with a hole C;

[0012] A second valve sleeve is provided in the first valve sleeve, a first valve core is provided in the second valve sleeve, one end of the first valve core extends out of the second valve sleeve and abuts against hole A, a first spring seat, a second spring seat and a pressure-adjusting screw are provided in sequence on one side of the first valve core, a first spring is provided between the first valve core and the first spring seat, and a second spring is provided between the second spring seat and the pressure-adjusting screw.

[0013] The first valve core is provided with a first through hole, and the hole A is connected to the inner cavity of the first valve sleeve through the first through hole;

[0014] A guide hole is provided on the end surface of the first spring seat away from the A hole, and a second valve core is provided in the guide hole. One end of the second valve core extends out of the guide hole and is provided with a conical portion, the bottom surface of the conical portion abuts against the second spring seat.

[0015] In the aforementioned multifunctional valve for a closed hydraulic plunger variable pump, the guide hole is a blind hole, a second through hole connected to the guide hole is provided on the side wall of the first spring seat, and a guide column that is gap-matched with the guide hole is provided at the upper end of the second valve core, and the second through hole is located between the guide column and the conical portion.

[0016] In the aforementioned multifunctional valve for a closed hydraulic plunger variable displacement pump, the pressure regulating screw is connected to the threaded sleeve via a screw plug, and a locking nut is provided at the outer end of the pressure regulating screw.

[0017] In the aforementioned multifunctional valve for a closed hydraulic plunger variable displacement pump, the first valve core is connected to the conical surface of hole A.

[0018] In the aforementioned multifunctional valve for a closed hydraulic plunger variable displacement pump, the inner hole of the second valve sleeve is a stepped hole, and a retaining ring fixed to the first valve core is provided on the stepped bottom surface of the second valve sleeve;

[0019] The end surface of the second valve sleeve close to the A hole is located at the B hole.

[0020] In the aforementioned multifunctional valve for a closed hydraulic plunger variable displacement pump, the first spring seat is fixed between the first valve sleeve and the screw sleeve.

[0021] The above-mentioned method of using the multifunctional valve is to use two multifunctional valves on a closed hydraulic plunger variable pump, and the two multifunctional valves are respectively recorded as valve 1 and valve 2.

[0022] The A hole of valve one is connected to the B port of the closed hydraulic plunger variable pump, the A hole of valve two is connected to the A port of the closed hydraulic plunger variable pump, the B hole of valve one is connected to the B hole of valve two, and the C hole of valve one and the C hole of valve two are respectively connected to the two sides of the variable cylinder of the variable pump.

[0023] In the above-mentioned method of use, the overflow pressure of the high-pressure overflow valve is set by the first spring, the cut-off pressure of the cut-off valve is set by the second spring and the rotating pressure-adjusting screw, and the bypass function is achieved by rotating the screw plug counterclockwise to drive the pressure-adjusting screw to rotate counterclockwise.

[0024] Compared to existing technologies, the present invention integrates the functions of a relief valve, a shut-off valve, an oil supply valve, and a check valve, effectively reducing the number of intersecting oil circuits in the end cover of a closed-type plunger variable pump, simplifying oil circuit layout and processing complexity, and lowering processing costs. Furthermore, the present invention boasts a relatively simple structure, with no components requiring high coaxiality, reducing processing complexity and resulting in lower costs. Therefore, the present invention offers the advantages of reducing both the processing cost of the variable pump end cover and its own inherent cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present invention.

[0026] Figure 2 It is a hydraulic principle diagram of the present invention in use.

[0027] The marks in the accompanying drawings are: 1-locking nut 2-screw plug, 3-screw sleeve, 4-pressure adjusting screw, 5-second spring, 6-second valve core, 7-second spring seat, 8-first spring seat, 9-retaining ring, 10-first spring, 11-second valve sleeve, 12-first valve core, 13-first valve sleeve, 14-first through hole, 15-guide hole, 16-conical part, 17-second through hole, 18-guide column, 19-valve one, 20-valve two. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0029] Example. A multifunctional valve for a closed hydraulic plunger variable pump, such as Figure 1 As shown, it includes a first valve sleeve 13, and the upper end of the first valve sleeve 13 is provided with a hole A ( Figure 1 As shown in A in the middle), the side wall of the first valve sleeve 13 is provided with a B hole ( Figure 1 As shown in B), the lower end of the first valve sleeve 13 is provided with a screw sleeve 3, the first valve sleeve 13 is screwed to the screw sleeve 3, and the side wall of the screw sleeve 3 is provided with a C hole ( Figure 1 (as shown in C in the middle).

[0030] A second valve sleeve 11 is provided in the first valve sleeve 13, and a first valve core 12 is provided in the second valve sleeve 11. One end of the first valve core 12 extends out of the second valve sleeve 11 and abuts against hole A. A first spring seat 8, a second spring seat 7 and a pressure-adjusting screw 4 are provided in sequence on one side of the first valve core 12. A first spring 10 is provided between the first valve core 12 and the first spring seat 8, and a second spring 5 is provided between the second spring seat 7 and the pressure-adjusting screw 4.

[0031] A first through hole 14 is provided on the first valve core 12 , and hole A is connected to the inner cavity of the first valve sleeve 13 through the first through hole 14 . The first through hole 14 is a stepped hole with a smaller top and a larger bottom. The upper end of the first spring 10 abuts against the stepped bottom surface of the first through hole 14 .

[0032] A guide hole 15 is provided on the lower end surface of the first spring seat 8, and a second valve core 6 is provided in the guide hole 15. The lower end of the second valve core 6 extends out of the guide hole 15 and is provided with a conical portion 16 with a smaller upper portion and a larger lower portion. The bottom surface of the conical portion 16 abuts against the second spring seat 7.

[0033] The guide hole 15 is a blind hole, and a second through hole 17 communicating with the guide hole 15 is provided on the side wall of the first spring seat 8. The upper end of the second valve core 6 is provided with a guide column 18 that is clearance-matched with the guide hole 15, and the second through hole 17 is located between the guide column 18 and the conical portion 16.

[0034] The pressure-adjusting screw 4 is connected to the threaded sleeve 3 via the screw plug 2. The pressure-adjusting screw 4 axially passes through the screw plug 2. The pressure-adjusting screw 4 is threadedly connected to the screw plug 2, and the screw plug 2 is threadedly connected to the threaded sleeve 3. A locking nut 1 is provided at the lower end of the pressure-adjusting screw 4. After loosening the locking nut 1, the pressure-adjusting screw 4 can be rotated to adjust the preload force of the second spring 5.

[0035] The first valve core 12 is connected to the conical surface of hole A.

[0036] The inner hole of the second valve sleeve 11 is a stepped hole, and a retaining ring 9 fixed to the first valve core 12 is provided on the stepped bottom surface of the second valve sleeve 11;

[0037] The upper end surface of the second valve sleeve 11 is located at the B hole.

[0038] The first spring seat 8 is fixed between the first valve sleeve 13 and the screw sleeve 3 .

[0039] The working principle of the multifunctional valve: Figure 1 As shown, when pressure in port A is high and pressure in port B is low, the first spring 10 acts to block port A with the first valve core 12, preventing oil from port B from entering port A. The multifunctional valve functions as a one-way valve. As the pressure in port A increases, high-pressure oil flows from port A, enters the inner cavity of the second valve sleeve 11 through the first through-hole 14, and then enters the guide hole 15 through the second through-hole 17. The oil then passes through the gap between the guide post 18 and the guide hole 15, reaching the upper side of the guide post 18. This pushes the second valve core 6 downward, overcoming the elastic force of the second spring 5. The conical portion 16 separates from the first spring seat 8, opening the second valve core 6 and allowing oil to be discharged from port C. The multifunctional valve functions as a shut-off valve. When the pressure in port A continues to rise until it reaches the relief pressure, the first valve core 12 moves downward, overcoming the elastic force of the first spring 10, allowing oil from port A to flow out of port B, achieving high-pressure relief and unloading. The multifunctional valve functions as a relief valve.

[0040] When low-pressure oil is in hole A and high-pressure oil is in hole B, the high-pressure oil enters from hole B and acts on the upper end surface of the second valve sleeve 11. When the pressure difference between holes A and B reaches a certain level, the high-pressure oil pushes the second valve sleeve 11 to move downward. The second valve sleeve 11 drives the first valve core 12 to move downward through the retaining ring 9 to overcome the elastic force of the first spring 10. The first valve core 12 opens, and the oil in hole B enters into hole A. The multi-function valve functions as an oil replenishing valve.

[0041] By rotating the screw plug 2 counterclockwise, the pressure regulating screw 4 is driven to rotate counterclockwise, reducing the preload force of the second spring, causing the second valve core 6 to drop in height, the second valve core 6 to open, and the oil is discharged from the C hole. The multifunctional valve then functions as a bypass valve.

[0042] The method of using the multifunctional valve is as follows: Figure 2 As shown, two multifunctional valves are used on a closed hydraulic plunger variable pump, and the two multifunctional valves are respectively denoted as valve 19 and valve 2 20. The A hole of valve 19 is connected to the B port of the closed hydraulic plunger variable pump, the A hole of valve 2 20 is connected to the A port of the closed hydraulic plunger variable pump, the B hole of valve 19 is connected to the B hole of valve 2, the A hole of valve 19 is connected to the B port of the closed hydraulic plunger variable pump, the A hole of valve 2 20 is connected to the A port of the closed hydraulic plunger variable pump, the B hole of valve 19 is connected to the B hole of valve 2 20, and the C hole of valve 19 and the C hole of valve 2 20 are respectively connected to the two sides of the variable cylinder of the variable pump.

[0043] For example, consider the high-pressure port A and low-pressure port B of a closed-loop hydraulic piston variable displacement pump: Valve 19 functions as a charge valve, Valve 202 acts as a shutoff or relief valve, and the check valve 20 is closed. When the pressure at port A reaches the cutoff pressure set by Valve 20, Valve 20 functions as a shutoff valve, and the oil in Port A of Valve 20 is discharged through Port C. This connects the control oil to the variable displacement cylinder and pushes the swash plate back to center, resulting in zero pump output. When the pressure at port A continues to increase, reaching the relief pressure set by Valve 20, Valve 20 functions as a relief valve, connecting Ports A and B of Valve 20. Oil in Port A enters Valve 20 through Port A and is discharged through Port B of Valve 20, achieving a high-pressure relief unloading function.

Claims

1. A multifunctional valve for a closed hydraulic plunger variable pump, characterized by: It comprises a first valve sleeve (13), one end of the first valve sleeve (13) is provided with a hole A, a side wall of the first valve sleeve (13) is provided with a hole B, the other end of the first valve sleeve (13) is provided with a screw sleeve (3), and a side wall of the screw sleeve (3) is provided with a hole C; A second valve sleeve (11) is provided in the first valve sleeve (13), a first valve core (12) is provided in the second valve sleeve (11), one end of the first valve core (12) extends out of the second valve sleeve (11) and abuts against the A hole, a first spring seat (8), a second spring seat (7) and a pressure regulating screw (4) are provided on one side of the first valve core (12), a first spring (10) is provided between the first valve core (12) and the first spring seat (8), and a second spring (5) is provided between the second spring seat (7) and the pressure regulating screw (4); The first valve core (12) is provided with a first through hole (14), and the hole A is connected to the inner cavity of the first valve sleeve (13) through the first through hole (14); A guide hole (15) is provided on the end surface of the first spring seat (8) away from the A hole, a second valve core (6) is provided in the guide hole (15), one end of the second valve core (6) extends out of the guide hole (15) and is provided with a conical portion (16), the bottom surface of the conical portion (16) abuts against the second spring seat (7); The guide hole (15) is a blind hole. A second through hole (17) communicating with the guide hole (15) is provided on the side wall of the first spring seat (8). A guide post (18) having a clearance fit with the guide hole (15) is provided at the upper end of the second valve core (6). The second through hole (17) is located between the guide post (18) and the conical portion (16).

2. The multifunctional valve for a closed hydraulic plunger variable displacement pump according to claim 1, characterized in that: The pressure regulating screw (4) is connected to the threaded sleeve (3) via the threaded plug (2), and a locking nut (1) is provided at the outer end of the pressure regulating screw (4).

3. The multifunctional valve for a closed hydraulic plunger variable displacement pump according to claim 1, characterized in that: The first valve core (12) is connected to the conical surface of hole A.

4. The multifunctional valve for a closed hydraulic plunger variable displacement pump according to claim 1, characterized in that: The inner hole of the second valve sleeve (11) is a stepped hole, and a retaining ring (9) fixed to the first valve core (12) is provided on the stepped bottom surface of the second valve sleeve (11); The end surface of the second valve sleeve (11) close to the A hole is located at the B hole.

5. The multifunctional valve for a closed hydraulic plunger variable displacement pump according to claim 1, characterized in that: The first spring seat (8) is fixed between the first valve sleeve (13) and the screw sleeve (3).

6. The method for using the multifunctional valve according to any one of claims 1 to 5, characterized in that: Two multifunctional valves are used on a closed hydraulic plunger variable pump. The two multifunctional valves are respectively denoted as valve 1 (19) and valve 2 (20). The A hole of valve one (19) is connected to the B port of the closed hydraulic plunger variable pump, the A hole of valve two (20) is connected to the A port of the closed hydraulic plunger variable pump, the B hole of valve one (19) is connected to the B hole of valve two (20), and the C hole of valve one (19) and the C hole of valve two (20) are respectively connected to the two sides of the variable cylinder of the variable pump.

7. The method of use according to claim 6, characterized in that: The overflow pressure of the high-pressure overflow valve is set by the first spring (10), the cut-off pressure of the cut-off valve is set by the second spring (5) and the rotating pressure regulating screw (4), and the bypass function is achieved by rotating the screw plug (2) counterclockwise to drive the pressure regulating screw (4) to rotate counterclockwise.

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