Constant flow valve for gear pump

Abstract

The utility model discloses a constant flow valve for gear pump belongs to hydraulic control technical field. The valve includes valve body, overflow valve assembly, reset spring, end cover, damping screw, throttle screw and limit screw. Valve body is equipped with oil inlet P, oil outlet A and oil return chamber T. Overflow valve assembly is installed in the inner chamber of valve body, and the upper end surface thereof forms A1 chamber with valve body, and the valve core thereof is equipped with oil channel that is communicated with the oil inlet and the oil return chamber area. The oil circuit between the oil inlet and the oil outlet is provided with throttle screw to form throttle section. The oil outlet is communicated with A1 chamber through the small hole of damping screw. Reset spring acts on the upper end surface of overflow valve assembly, and limit screw limits its stroke from the bottom. The utility model drives overflow valve assembly action through the pressure difference of throttling and realizes the constant output flow. Through the cooperation of built-in overflow valve and damping hole, the output is rapidly reduced when the load is too high, and overload protection is realized. The valve can directly replace the rear cover of gear pump and be integrated into constant flow pump, and the structure is compact and reliable.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic control technology, and in particular to a constant flow valve for a gear pump. Background Technology

[0002] In construction machinery and transport vehicles such as excavators, cranes, and trucks, steering systems typically use fixed-displacement gear pumps as the hydraulic power source. The output flow rate of this type of gear pump is directly proportional to its input speed, i.e., Q = q × n (where Q is the flow rate, q is the displacement, and n is the speed). Engines operate over a wide speed range, varying significantly from idle to maximum speed, causing substantial fluctuations in the gear pump's output flow rate. In existing technology, when the engine is running at high speed, the excessive output flow rate of the gear pump can lead to excessively high steering speeds, posing a safety hazard. Furthermore, when the steering load suddenly increases (e.g., when encountering an obstacle), the system pressure rises sharply, which, without a protection mechanism, can easily damage hydraulic components. To solve these problems, it is usually necessary to install independent flow control valves and relief valves in the system, which not only increases system complexity and installation space but also raises costs. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned technical problems and provide a constant flow valve for gear pumps.

[0004] In order to achieve the above technical objectives and meet the above technical requirements, the technical solution adopted by this utility model is: a constant flow valve for a gear pump, characterized in that it includes a valve body, an overflow assembly, a return spring, an end cover, a damping screw, a throttling screw and a limiting screw; The valve body is provided with an oil inlet P, an oil outlet A, and an oil return chamber T; The overflow valve assembly is axially installed in the inner cavity of the valve body. Its upper end face and the inner wall of the valve body together form cavity A1, and its lower end face and the valve body form a region that communicates with the return oil cavity T. The valve core of the overflow valve assembly is provided with an oil passage that connects the oil inlet P and the region that communicates with the return oil cavity T. The end cap is fixed to the top of the valve body, and the return spring is located inside the end cap. The lower end of the return spring acts on the upper end face of the overflow valve assembly. The damping screw is installed on the valve body and has a damping hole inside, which connects the oil outlet A and the A1 chamber. The throttling screw is installed on the valve body and forms a throttling section in the oil passage between the oil inlet P and the oil outlet A. The throttling area of ​​the throttling section is S0. The limiting screw is screwed into the threaded hole at the bottom of the valve body, and its end extending into the inner cavity is located below the overflow valve assembly.

[0005] Preferably, the upper end face of the valve core of the overflow valve assembly is in fluid communication with the A1 cavity, forming an upper pressure bearing surface; the lower end face or side wall of the valve core is in fluid communication with the oil inlet P, forming a lower pressure bearing surface.

[0006] Preferably, the diameter of the damping hole in the damping screw is 0.8mm-1.2mm.

[0007] Preferably, a first O-ring is provided between the valve body and the limiting screw, and a second O-ring is provided between the end cap and the valve body.

[0008] Compared with the traditional structure, the beneficial effects of this utility model are: 1. This utility model integrates constant flow control and overflow protection functions into a single valve body, and can replace the gear pump back cover as a whole. It can be directly assembled with the pump body, gears, etc. to form a "constant flow pump", which greatly simplifies the system pipeline, reduces leakage points, and significantly saves installation layout space in space-constrained environments such as engineering machinery.

[0009] 2. By generating differential pressure feedback through the throttle screw, the overflow valve assembly is driven to open and divert the flow, realizing automatic constant flow control so that the output flow does not increase indefinitely with the speed, thus ensuring stable and safe steering speed.

[0010] 3. Through the synergistic effect of the built-in overflow valve and damping orifice, when the load pressure is too high, the diversion ratio can be rapidly increased, significantly reducing the flow and power output to the actuator, effectively preventing system overload damage.

[0011] 4. By replacing or adjusting the throttling screw, return spring (to adjust the preload), and limit screw, the required constant flow rate and overflow opening pressure can be easily set to meet the needs of different models and application scenarios. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a constant flow pump. Figure 2 This is a schematic diagram of the structure of this utility model; Figure 3 This is a schematic diagram of the overflow valve assembly of this utility model; Figure 4 A graph showing the relationship between engine speed and constant flow pump output flow rate; In the diagram: 1. Valve body, 2. Damping screw, 3. Relief valve assembly, 31. Valve core, 4. Throttling screw, 5. Limiting screw, 6. First O-ring seal, 7. Return spring, 8. End cap, 9. Second O-ring seal, 10. A1 chamber, 11. Constant flow valve, P. Oil inlet, A. Oil outlet, T. Return chamber. Detailed Implementation

[0013] The present invention will be further described below.

[0014] See attached document Figure 2 A constant flow valve for a gear pump, characterized in that it includes a valve body 1, an overflow assembly 3, a return spring 7, an end cap 8, a damping screw 2, a throttling screw 4, and a limit screw 5; The valve body 1 is provided with an oil inlet P, an oil outlet A, and an oil return chamber T; The overflow valve assembly 3 is axially installed in the inner cavity of the valve body 1. Its upper end face and the inner wall of the valve body 1 together form cavity A1 10, and its lower end face and the valve body 1 form a region communicating with the return oil cavity T. The valve core 31 of the overflow valve assembly 3 is provided with an oil passage that connects the oil inlet P and the region communicating with the return oil cavity T. The end cap 8 is fixed to the top of the valve body 1, and the return spring 7 is disposed inside the end cap 8. The lower end of the return spring 7 acts on the upper end face of the overflow valve assembly 3. The damping screw 2 is installed on the valve body 1, and a damping hole is provided inside it. The damping hole connects the oil outlet A and the A1 chamber 10. The throttling screw 4 is installed on the valve body 1 and forms a throttling section in the oil passage between the oil inlet P and the oil outlet A. The throttling area of ​​the throttling section is S0. The limiting screw 5 is screwed into the threaded hole at the bottom of the valve body 1, and its end extending into the inner cavity is located below the overflow valve assembly 3.

[0015] In this preferred embodiment, the upper end face of the valve core 31 of the overflow valve assembly 3 is in fluid communication with the A1 cavity 10, forming an upper pressure bearing surface; the lower end face or side wall of the valve core 31 is in fluid communication with the oil inlet P, forming a lower pressure bearing surface.

[0016] In this preferred embodiment, the diameter of the damping hole in the damping screw 2 is 0.8mm-1.2mm.

[0017] In this preferred embodiment, a first O-ring 6 is provided between the valve body 1 and the limiting screw 5, and a second O-ring 9 is provided between the end cap 8 and the valve body 1.

[0018] Working principle and process: 1. Implementation of constant current function (refer to) Figure 2 , Figure 4 ): The pressurized oil output from the gear pump enters through the inlet P, flows through the throttling orifice (area S0) of the throttling screw 4, and exits through the outlet A, driving the actuator. This process generates a pressure difference ΔP between the inlet P and the outlet A. The pressure at the outlet A is transmitted to the A1 chamber through the damping orifice of the damping screw 2, so the pressure difference between the inlet P and the A1 chamber is also ΔP. This pressure difference ΔP acts on the pressure-bearing surface of the valve core 31 of the relief valve assembly 3, generating an upward thrust, which balances the downward preload of the return spring 7.

[0019] When the engine speed is low and the flow rate is low, ΔP is small, and valve core 31 closes under the action of spring force, so the oil inlet P and the oil return chamber T are not connected.

[0020] As the engine speed increases, the pump output flow increases, and ΔP increases proportionally. When ΔP increases to the point of overcoming the preload of the return spring 7, it pushes the overflow valve assembly 3 to move upward as a whole, opening the oil passage on its valve core 31, so that the oil inlet P is connected to the return oil chamber T, and part of the pressurized oil is diverted back to the return oil chamber T.

[0021] This negative feedback automatically limits and stabilizes the actual flow rate entering the oil outlet A through the throttling orifice S0 at a certain maximum value, such as... Figure 4 As shown, in a specific embodiment, the constant flow rate can be stabilized at approximately 32 L / min. At this point, the input flow rate at the oil inlet P can be much higher than this value, thereby reliably limiting the maximum speed of the actuator and ensuring operational safety. Different desired constant flow rates can be obtained by replacing the throttling screw 4 with one having a different throttling area S0, adjusting the preload of the return spring 7, or setting the maximum stroke of the relief valve assembly 3 via the limit screw 5.

[0022] 2. Implementation of overload protection function (refer to...) Figure 2 , Figure 3 ): The overflow valve assembly 3 has an internal opening pressure. When the load pressure at the oil outlet A exceeds this pressure, its internal pilot valve opens, and the oil in chamber A1 10 quickly overflows to the return oil chamber T.

[0023] Due to the throttling effect of the damping screw 2's damping orifice, an additional pressure difference ΔP1 is generated between the oil outlet A and chamber A1 10. This causes the total pressure difference between the oil inlet P and chamber A1 10 to increase dramatically to (ΔP + ΔP1), pushing the main valve core of the relief valve assembly 3 to move further upward significantly, and the opening of the main relief channel between the oil inlet P and the return oil chamber T to expand sharply.

[0024] Most of the high-pressure oil from the gear pump is directly returned to the return chamber T, and the output flow at outlet A rapidly drops to an extremely low level, causing a sharp drop in system power and thus achieving automatic overload protection for the hydraulic system. The opening pressure of the relief valve can be set according to the maximum allowable pressure of the system.

[0025] In practical implementation, the constant flow valve 11 of this utility model directly replaces the rear cover of the gear pump and is assembled with the pump body, driving gear, driven gear, etc. to form a constant flow pump (see reference). Figure 1 This constant flow pump is installed in the steering system of construction machinery. Its inlet P is connected to the gear pump outlet, its outlet A is connected to the steering cylinder, and its return chamber T is connected to the pump's suction port. When the engine speed changes, the constant flow valve 11 can automatically limit the maximum output flow to ensure steering safety; when the load is too high, it can quickly reduce the output to protect the system.

[0026] The above embodiments of this utility model are merely examples to clearly illustrate this utility model, and are not intended to limit the scope of protection of this utility model. All equivalent technical solutions also fall within the scope of this utility model, and the patent protection scope of this utility model should be defined by each claim.

Claims

1. A constant flow valve for a gear pump, characterized in that, Includes valve body (1), overflow valve assembly (3), return spring (7), end cap (8), damping screw (2), throttle screw (4) and limit screw (5); The valve body (1) is provided with an oil inlet (p), an oil outlet (A), and an oil return chamber (T); The overflow valve assembly (3) is axially installed in the inner cavity of the valve body (1). Its upper end face and the inner wall of the valve body (1) together form cavity A1 (10), and its lower end face and the valve body (1) form a region communicating with the return oil chamber (T). The valve core (31) of the overflow valve assembly (3) is provided with an oil passage that connects the oil inlet (p) and the region communicating with the return oil chamber (T). The end cap (8) is fixed to the top of the valve body (1), and the return spring (7) is located inside the end cap (8). The lower end of the return spring (7) acts on the upper end face of the overflow valve assembly (3). The damping screw (2) is installed on the valve body (1), and a damping hole is provided inside it. The damping hole connects the oil outlet (A) and the A1 chamber (10). The throttling screw (4) is installed on the valve body (1) and forms a throttling section in the oil passage between the oil inlet (p) and the oil outlet (A), with a throttling area of ​​S0. The limiting screw (5) is screwed into the threaded hole at the bottom of the valve body (1), and its end extending into the inner cavity is located below the overflow valve assembly (3).

2. The constant flow valve for a gear pump according to claim 1, characterized in that: The upper end face of the valve core (31) of the overflow valve assembly (3) is in fluid communication with the A1 cavity (10) to form an upper pressure bearing surface; the lower end face or side wall of the valve core (31) is in fluid communication with the oil inlet (p) to form a lower pressure bearing surface.

3. A constant flow valve for a gear pump according to claim 1, characterized in that: The diameter of the damping hole in the damping screw (2) is 0.8mm-1.2mm.

4. A constant flow valve for a gear pump according to claim 1, characterized in that: A first O-ring (6) is provided between the valve body (1) and the limiting screw (5), and a second O-ring (9) is provided between the end cap (8) and the valve body (1).

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