A spool valve assembly for a pressure servo valve

Abstract

A kind of spool valve assembly for pressure servo valve, valve core is located in valve body, and valve sleeve is sleeved on valve core.The bushing is between the outer surface of the oil inlet end of valve core and the inner surface of valve sleeve.The valve core oil inlet control cavity is formed between the inner end surface of shaft sleeve and the end surface of the oil inlet end of valve core.The valve core oil return control cavity is formed between the inner end surface of valve sleeve plug and the end surface of valve core.The invention receives two-way pressure from pilot stage through two control cavities, generates control pressure difference at both ends of valve core, moves valve core to valve core oil return control cavity, gradually closes the oil return pressure hole R of valve core, gradually opens brake pressure hole S, gradually increases output port pressure, until the control force acting on valve core, brake cavity pressure feedback balance, thus output a brake pressure proportional to input current, so that the stability of the output pressure of servo valve is improved from 5% to 3%, the processability of pressure servo valve is improved, and the stability of pressure servo valve is improved.

Description

Technical Field

[0001] This invention relates to the field of servo valve technology, specifically a spool valve assembly for improving the manufacturability of servo valves and enhancing the stability of pressure servo valves. Background Technology

[0002] Pressure servo valves, as precision hydraulic components for controlling output pressure, are widely used in aircraft wheel brakes. With technological advancements, various structural forms of pressure servo valves are increasingly employed. However, the poor pressure stability of servo valves severely impacts mainframe assembly and aircraft operation.

[0003] A current signal is input to the torque motor coil, and the torque motor converts the electrical signal into mechanical motion. The amplifier outputs different control pressures to the two control chambers according to the mechanical motion, and forms a dynamic balance through the slide valve assembly to realize closed-loop control of the slide valve stage, ensuring that the output pressure is proportional to the input current.

[0004] The patents CN112709724 A and CN108716489 disclose a power stage structure for an electro-hydraulic pressure servo valve, and CN106337851B disclose a deflector jet type brake pressure valve. The common principle of the spool valve assembly in these three patents is that the two control chambers receive two pressures from the pilot stage to form a control pressure difference, which causes the valve core to move under force and open the oil inlet to start building output pressure. At the same time, the output pressure passes through the valve core hole to the valve core feedback surface, and the return oil pressure passes through the valve core hole to the valve core feedback surface, forming a dynamic balance with the control pressure difference, spring force, and return oil pressure. In the same hydraulic system, the return oil pressure is a constant value, realizing closed-loop control of the spool valve stage and ensuring that the brake pressure is proportional to the input current (the formula is simplified to S=K(i-Δi)+R, where S is the brake pressure, R is the return oil pressure, i is the control current, Δi is the dead zone current, and K is a coefficient related to the inlet pressure and structural parameters). Its structural drawback is that the return oil pressure participates in the dynamic balance, and the return oil pressure has a significant impact on the stability of the brake pressure. Furthermore, the spool valve assembly consists of a valve core, valve sleeve, valve body, and bushing. During assembly, the valve core, valve sleeve, and bushing undergo mutual fitting, requiring secondary matching with a precision requirement of ten-thousandths of a percent. The valve body and valve sleeve are tightly fitted, requiring an interference fit of 0.001 to 0.003 mm. This increases the difficulty of selection and reduces the success rate of successful matching. Simultaneously, the stringent fitting quality results in greater difficulty in assembling and debugging the servo valve, leading to poor stability. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, such as poor manufacturability and stability, and high debugging difficulty, this invention proposes a spool valve assembly for pressure servo valves.

[0006] This invention includes a valve core, a valve sleeve, a valve body, a valve sleeve plug, a return oil end cap, a valve core return oil control chamber, a valve core inlet oil control chamber, a butterfly spring, a bushing, an inlet oil end cap, and a bushing. Wherein:

[0007] The valve core is located within the valve body, and a valve sleeve is fitted onto the outer circumferential surface of the valve core. A bushing is positioned between the outer circumferential surface of the valve core's oil inlet end and the inner circumferential surface of the valve sleeve, with a positioning plate on the end face of the bushing fitting against the end face of the valve sleeve. A bushing is located at the oil inlet end of the valve core, with the inner end face of a disc spring located within the bushing fitting against the outer end face of the bushing; thus, a valve core oil inlet control cavity is formed between the inner end face of the bushing and the oil inlet end face of the valve core. The length between the small end face of the bushing and the oil inlet end face of the valve core is 2.15 mm. An oil inlet end cap is fitted onto the outer circumferential surface of the bushing, thereby securing the bushing; a bushing washer is located between the oil inlet end cap and the adjacent end face of the bushing. A valve sleeve plug is located on the oil return end face of the valve core, with a gap between the inner end face of the valve sleeve plug and the adjacent valve core end face, forming the valve core oil return control cavity. The oil return end cap is located on the outer end face of the valve sleeve plug. The upper sliding valve assembly is provided with an oil inlet pressure port, an oil return pressure port, and a brake pressure port.

[0008] The valve core has an annular groove 2.1 mm long and 5.8 mm in diameter on its circumferential surface near the oil inlet end. A 1 mm diameter pressure feedback hole is located within this groove, leading to the center of the valve core. In the center of the valve core, there is an annular groove 11.8 mm long and 1.55 mm deep. The cavity between this groove and the inner surface of the valve sleeve forms a brake pressure chamber for brake pressure output. A 1 mm diameter oblique hole in the brake pressure chamber connects to the valve core's oil inlet control chamber, forming a pressure feedback chamber for closed-loop brake pressure control. Near the return end of the valve core, there is also an annular groove 1.5 mm long and 4.2 mm in diameter on its circumferential surface. The cavity between this groove and the inner surface of the valve sleeve forms a return oil chamber for return oil pressure output. Pressure equalization grooves are located on the circumferential surfaces at both ends of the valve core to prevent valve core jamming caused by uneven pressure. The outer circumferential surface at the oil inlet end of the valve core is a stepped surface, and the height difference of this adjustment is the same as the thickness of the bushing housing.

[0009] The nozzle oil inlet control chamber is formed by the space between one end face of the valve sleeve, the inner end face of the oil inlet end cover, and the valve body oil cavity. The oil in the valve body cavity is introduced into the valve core oil inlet control chamber through the nozzle oil inlet control chamber. The nozzle oil return control chamber is formed by the other end face of the valve sleeve and the valve body oil cavity. The oil in the valve body cavity is introduced into the valve core oil return control chamber.

[0010] The valve sleeve housing has an inlet pressure port P, a return pressure port R, and an output pressure port S for the spool valve assembly. The inlet pressure port is located near the inlet end of the valve core, and the return pressure port is located near the return end of the valve core. The brake pressure port is located between the inlet pressure port and the return pressure port, at the center of the valve sleeve's axial direction. The opening of the inlet pressure port is formed within a groove on the outer circumferential surface of the valve sleeve, creating an inlet chamber. The opening of the return pressure port is also formed within a groove on the outer circumferential surface of the valve sleeve, creating a return chamber. The position of the brake pressure port corresponds to the groove on the center circumferential surface of the valve sleeve.

[0011] The inner diameter of the bushing is the same as the outer diameter of the valve core at the oil inlet end, and the outer diameter of the bushing is the same as the inner diameter of the valve sleeve. When the bushing is installed on the valve core, a clearance fit is formed between the two. There is a radially protruding positioning plate on the outer end face of the bushing, and the outer diameter of the positioning plate is slightly smaller than the diameter of the valve sleeve at the oil inlet control chamber end.

[0012] The oil inlet end cap is plate-shaped. An axial sleeve is located on the inner end face of the oil inlet end cap, forming an oil inlet end cap sheath. The axial length of this sheath is slightly greater than the length of the bushing but less than the sum of the lengths of the bushing and the bushing washer, and it is used to install the bushing and the bushing washer. When the oil inlet end cap is fitted onto the bushing, an annular nozzle oil inlet control chamber C3 is formed between the inner end face of the oil inlet end cap and the outer end face of the valve sleeve, and this nozzle oil inlet control chamber communicates with the valve core oil inlet control chamber.

[0013] After the valve sleeve is fitted with the sealing ring and protective ring, it has a clearance fit with the valve body; the valve core and valve sleeve are ground together with a clearance of 0.001 to 0.003; the bushing and valve core have a clearance of 0.002 to 0.004; the bushing and valve sleeve are ground together again with a clearance of 0.001 to 0.003; after the valve sleeve is fitted with the sealing ring, it has a clearance fit with the valve body.

[0014] During the operation of the pressure servo valve, the working state of the spool valve assembly is as follows: When oil is supplied to the pressure servo valve, the oil inlet is divided into two paths: one path supplies the motor pre-stage, and the other path P supplies the spool valve stage. The oil in the motor pre-stage is distributed through the nozzle assembly into the nozzle return oil control chamber and the nozzle inlet oil control chamber. The oil in the nozzle return oil control chamber acts on the valve core return oil control end face through the valve core return oil control chamber, and the oil in the nozzle inlet oil control chamber acts on the valve core inlet oil control end face through the valve inlet oil control chamber.

[0015] When the aircraft is in a non-braking control state, the servo valve torque motor has no input current signal. The baffle position is biased towards the nozzle oil inlet control chamber position and is used as the initial position. The pressure in the nozzle oil inlet control chamber is greater than the pressure in the nozzle oil return control chamber, so the force of the valve core oil inlet control chamber on the valve core end face is greater than the force of the valve core oil return control chamber on the valve core end face. Therefore, the valve core is pushed to the valve sleeve blockage end position, the brake pressure hole S and the oil return hole R are connected, there is no braking force, that is, the non-braking state.

[0016] When the aircraft is in braking control mode, the torque motor inputs a current signal. Under the action of electromagnetic force, the baffle shifts towards the nozzle oil inlet and outlet control chamber. The pressure in the nozzle oil outlet control chamber gradually increases, while the pressure in the nozzle oil inlet control chamber gradually decreases. This makes the force acting on the valve core oil inlet control chamber end face less than the force on the valve core oil outlet control chamber end face. The valve core moves towards the bushing end, and the valve core oil outlet pressure hole R gradually closes while the brake pressure hole S gradually opens. Pressurized oil connects to the brake pressure hole S through the oil inlet pressure hole P, and the brake pressure gradually increases until the control force and feedback force acting on the valve core are balanced. The brake pressure hole S maintains a certain opening, outputting a constant brake pressure, i.e., the braking state. When the input current is cut off, the baffle returns to its initial position. The pressure in the nozzle oil inlet control chamber is greater than the pressure in the nozzle oil outlet control chamber, making the force on the valve core oil inlet control chamber end face greater than the force on the valve core oil outlet control chamber end face. Therefore, the valve core is pushed to the valve sleeve blockage end position, the brake pressure hole S and the oil outlet R are connected, there is no braking force, and the aircraft returns to the non-braking state.

[0017] In this invention: the oil circuit structure is modified by the valve core, eliminating the need for a return oil feedback chamber. A valve sleeve plug replaces the large-end bushing and plug in the prior art. A clearance fit is used between the valve sleeve and the valve body, and a sealing ring ensures a tight seal. A butterfly spring replaces the return spring, bushing, and plug, and a bushing washer adjusts the distance between the bushing and the butterfly spring, preventing blockage of the oil circuit passage when the valve sleeve, valve sleeve plug, and bushing are affected by thermal expansion and contraction and stress release.

[0018] This invention receives two pressures from the pilot stage through two control chambers, which generates a control pressure difference at both ends of the valve core. The valve core moves towards the valve core return oil control chamber, the return oil pressure port R of the valve core gradually closes, the brake pressure port S gradually opens, and the output pressure gradually increases until the control force acting on the valve core and the brake chamber pressure feedback are balanced, thus outputting a brake pressure that is proportional to the input current.

[0019] This invention optimizes the valve core structure and alters the oil circuit, eliminating the involvement of return oil in dynamic balancing, thus improving the stability of the servo valve's output pressure from 5% to 3%. Eliminating the large-end bushing reduces accumulated tolerances by ±0.05 due to assembly issues. The valve sleeve and valve body assembly is changed from a high-precision interference fit to a clearance fit, and a sealing structure ensures sealing performance, improving assembly processability and increasing the servo valve's assembly and debugging pass rate by 10%. Furthermore, it facilitates disassembly, avoiding product scrap due to maintenance.

[0020] This invention improves the manufacturability and stability of pressure servo valves. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the valve core structure.

[0023] Figure 3 This is a schematic diagram of the valve sleeve structure.

[0024] Figure 4 This is a schematic diagram of the valve body structure.

[0025] Figure 5 This is a schematic diagram of the valve sleeve blockage structure.

[0026] Figure 6 This is a schematic diagram of the oil return end cap structure.

[0027] Figure 7 This is a schematic diagram of the bushing structure.

[0028] Figure 8 This is a schematic diagram of the oil inlet end cap structure.

[0029] Figure 9 This is a schematic diagram of the bushing structure.

[0030] Figure 10 This is a schematic diagram of a pressure servo valve.

[0031] In the diagram: 1. Valve core; 2. Valve sleeve; 3. Valve body; 4. Valve sleeve plug; 5. Protective ring; 6. Oil return end cap; 7. Sealing ring; 8. Valve core oil return control chamber; 9. Valve core oil inlet control chamber; 10. Butterfly spring; 11. Bushing; 12. Bushing washer; 13. Oil inlet end cap; 14. Bushing; 15. Screw; P. Oil inlet pressure hole; S. Brake pressure hole; R. Oil return pressure hole; Brake pressure chamber C1; Pressure feedback chamber C2; C3. Nozzle oil return surface control chamber; C4. Nozzle oil inlet control chamber. Detailed Implementation

[0032] This embodiment is a spool valve assembly for a pressure servo valve, including a valve core 1, a valve sleeve 2, a valve body 3, a valve sleeve plug 4, a protective ring 5, an oil return end cap 6, a sealing ring 7, a valve core oil return control chamber 8, a valve core oil inlet control chamber 9, a butterfly spring 10, a bushing 11, a bushing washer 12, an oil inlet end cap 13, bushings 14 and 15, and screws.

[0033] Wherein: the valve core 1 is located inside the valve body 3, and a valve sleeve 2 is fitted on the outer circumferential surface of the valve core.

[0034] A bushing 14 is provided between the outer circumferential surface of the valve core 1 at the oil inlet end and the inner circumferential surface of the valve sleeve 2, and the positioning plate on the end face of the bushing is fitted to the end face of the valve sleeve. A bushing 11 is located at the oil inlet end of the valve core, and the inner end face of the disc spring 10 located within the bushing is fitted to the outer end face of the bushing; thus, a valve core oil inlet control chamber 9 is formed between the inner end face of the bushing and the end face of the valve core at the oil inlet end. The length between the small end face of the bushing and the end face of the valve core at the oil inlet end is 2.15 mm. An oil inlet end cap 13 is fitted onto the outer circumferential surface of the bushing 11, thereby securing the bushing; a bushing washer 12 is provided between the oil inlet end cap and the adjacent end face of the bushing. A valve sleeve plug 4 is provided on the end face of the valve core at the oil return end, and a gap exists between the inner end face of the valve sleeve plug and the adjacent end face of the valve core, forming a valve core oil return control chamber 8. The return end cap 6 is located on the outer end face of the valve sleeve blockage, thereby securing the valve sleeve blockage. The upper sliding valve assembly has an inlet pressure port, a return pressure port, and a brake pressure port.

[0035] The circumferential surface of the valve core 1 is stepped: the surface around the valve core near the oil inlet end has an annular groove 2.1 mm long and 5.8 mm in diameter, with a 1 mm diameter hole leading to the center of the valve core. The output pressure passes through the valve core hole to the valve core feedback surface for pressure feedback. In the center of the valve core, there is an annular groove 11.8 mm long and 1.55 mm deep; the cavity between this groove and the inner surface of the valve sleeve 2 forms a brake chamber C1 for brake pressure output. A 1 mm diameter oblique hole in the brake pressure chamber C1 leads to the valve core oil inlet control chamber 9 and then to a 6 mm diameter small shaft surface of the valve core, forming a pressure feedback chamber C2 for closed-loop brake pressure control. The circumferential surface of the valve core near the oil return end also has an annular groove 1.5 mm long and 4.2 mm in diameter; the cavity between this groove and the inner surface of the valve sleeve 2 forms a return oil chamber for return oil pressure output. There are pressure equalization grooves on the circumferential surfaces at both ends of the valve core to prevent valve core jamming caused by uneven pressure. The outer circumferential surface of the oil inlet end of the valve core is a stepped surface, and the height difference of this adjustment is the same as the thickness of the bushing housing.

[0036] The valve sleeve 2 is a hollow rotating body with the same inner diameter as the maximum diameter of the valve core. After the valve sleeve is fitted onto the valve core, the two are fitted with a clearance.

[0037] The nozzle oil inlet control chamber is formed by the space between one end face of the valve sleeve, the inner end face of the oil inlet end cover 13, and the valve body oil cavity. The oil in the valve body cavity is introduced into the valve core oil inlet control chamber 9 through the nozzle oil inlet control chamber. The nozzle oil return control chamber is formed by the other end face of the valve sleeve and the valve body oil cavity. The oil in the valve body cavity is introduced into the valve core oil return control chamber.

[0038] The inlet pressure port P, return pressure port R, and output pressure port S of the spool valve assembly are distributed on the valve sleeve housing. The inlet pressure port is near the inlet end of the valve core, and the return pressure port is near the return end of the valve core. The brake pressure port is located between the inlet pressure port and the return pressure port, in the middle of the valve sleeve's axial direction. The opening of the inlet pressure port is formed within a groove on the outer circumferential surface of the valve sleeve, creating an inlet chamber. The opening of the return pressure port is also formed within a groove on the outer circumferential surface of the valve sleeve, creating a return chamber. The position of the brake pressure port corresponds to the groove on the middle circumferential surface of the valve sleeve. Multiple sealing grooves are distributed on the circumferential surface of the valve sleeve.

[0039] The bushing 14 is sleeve-shaped, with its inner diameter being the same as the outer diameter of the valve core's oil inlet end. The outer diameter of the bushing is the same as the inner diameter of the valve sleeve, allowing for a clearance fit when the bushing is installed on the valve core. A radially protruding positioning plate is located on the outer end face of the bushing, with its outer diameter slightly smaller than the diameter of the valve sleeve's oil inlet control chamber end.

[0040] The valve sleeve plug 4 is cylindrical, with the same outer diameter as the valve sleeve 2. The circumferential surface of the valve sleeve plug has grooves for installing the sealing ring 7 and the protective ring 5. The inner circumferential surface of the valve sleeve plug is stepped, with a slotted groove at the center of the small end face. The radial height difference between the small and large diameter sections of the stepped surface and the slotted groove at the small end face communicate with the return oil control chamber 8. A threaded process hole is designed on the outer end face of the valve sleeve plug for disassembly.

[0041] The oil return end cap 6 is a circular block with a T-shaped cross-section. The outer diameter of the small-diameter end of the oil return end cap is inserted into the valve body 3 and fixed to the valve body via a threaded connection. A groove is cut at the center of the small-diameter end face, and a ring is designed to ensure a good fit between the small end face of the oil return end cap and the large end face of the valve sleeve plug. A hexagonal blind hole is designed at the center of the large-diameter end face of the oil return end cap 6 for disassembly. Six safety holes are distributed along the edge of the large-diameter end face, with one end of each hole located on the large-diameter end face of the oil return end cap and the other end located on the circumferential surface of the large-diameter end face, providing an anti-loosening design for the oil return end cap.

[0042] The oil inlet cap 13 is plate-shaped. An axial sleeve is located on the inner end face of the oil inlet cap, forming an oil inlet cap sheath. The axial length of this sheath is slightly greater than the length of the bushing but less than the sum of the lengths of the bushing and the bushing washer, and it is used to install the bushing and bushing washer. When the oil inlet cap is fitted onto the bushing, an annular nozzle oil inlet control chamber C3 is formed between the inner end face of the oil inlet cap 13, the outer end face of the valve sleeve 2, and the valve body oil cavity, and this nozzle oil inlet control chamber communicates with the valve core oil inlet control chamber 9. The outer circumferential surface of the oil inlet cap sheath has grooves for installing the sealing ring 7 and the protective ring 5. The oil inlet cap 14 is fixed to the valve body by screws 15.

[0043] The bushing washer 12 is an annular cylindrical shape, with an outer diameter slightly smaller than the inner diameter of the oil inlet end cover. It is used to adjust the valve core in its initial position to ensure that the pressure output hole and the oil return pressure hole are the same.

[0044] The butterfly spring 10 is sleeve-shaped, with an inner diameter slightly larger than that of the bushing 11. It is fitted onto the bushing, and the spring force of the butterfly spring pushes the bushing close to the small end face of the valve sleeve.

[0045] The valve body 3 is block-shaped, with its inner cavity used to install the valve core and valve sleeve. The shape of the inner cavity of the valve body matches the outer shape of the sliding sleeve. The valve body has a nozzle return oil control chamber C4, a nozzle inlet oil control chamber C3, an inlet pressure oil passage P, an output pressure hole S, and a return oil pressure hole R. The nozzle return oil control chamber C4 communicates with the valve core return oil control chamber 8, the nozzle inlet oil control chamber C3 communicates with the valve core inlet oil control chamber 9, and the output pressure hole S communicates with the valve core's brake pressure chamber C1. The valve body 3 has a through hole communicating with the return oil pressure hole on the valve sleeve 2, forming the return oil pressure hole R. When the valve core moves to the valve sleeve blockage end, the return oil pressure oil passage R communicates with the valve core's brake pressure chamber C1; when the valve core moves to the bushing small end face, the inlet pressure oil passage P communicates with the valve core's brake pressure chamber C1.

[0046] During assembly: The return oil end cap 6 is installed on the valve body 3 via threads. After the valve sleeve plug 4 is fitted with the sealing ring 7 and the protective ring 5, it has a clearance fit with the valve body. The valve core 1 and the valve sleeve 2 are ground to ensure a clearance of 0.001 to 0.003. The bushing has a clearance fit of 0.002 to 0.004 with the valve core. The bushing 14 and the valve sleeve 2 are ground a second time to ensure a clearance of 0.001 to 0.003. After the valve sleeve 2 is fitted with the sealing ring 7, it has a clearance fit with the valve body 3. After assembling the return oil end cap 6, the valve sleeve plug 4, the valve sleeve 2, the valve core 1, and the bushing 14, the dimension A from the end face of the oil inlet of the valve body 3 to the large end face of the bushing is measured. After the oil inlet end cap 13, the bushing washer 12, the bushing 11, and the disc spring 10 are combined, the dimension A1 from the end face of the oil inlet of the valve body 3 to the large end face of the bushing is measured in its natural state. The dimensions A1 are ensured by adjusting the specifications and quantity of the bushing washer 12 and the disc spring 10. The oil inlet cap 13 is mounted on the valve body by screws 15.

[0047] During the operation of the pressure servo valve, the working state of the spool valve assembly is as follows: When oil is supplied to the pressure servo valve, the oil inlet is divided into two paths: one supplying the motor pre-stage, and the other, P, supplying the spool valve stage. The oil supplied to the motor pre-stage (16) is distributed through the nozzle assembly (17) to the nozzle return control chamber (C4) and the nozzle inlet control chamber (C3). The oil in the nozzle return control chamber (C4) acts on the valve core return control end face through the valve core return control chamber (8), and the oil in the nozzle inlet control chamber (C3) acts on the valve core inlet control end face through the valve core inlet control chamber (9). Figure 10 As shown. When the aircraft is in a non-braking control state, the servo valve torque motor has no input current signal, and the position of baffle 19 is biased towards the nozzle oil inlet control chamber and serves as the initial position. The pressure in the nozzle oil inlet control chamber C3 is greater than the pressure in the nozzle oil return control chamber C4, causing the force on the valve core end face of the valve core oil inlet control chamber to be greater than the force on the valve core end face of the valve core oil return control chamber. Therefore, the valve core is pushed to the valve sleeve blockage end position, and the brake pressure hole S and the oil return hole R are connected, resulting in no braking force, i.e., a non-braking state. When in a braking control state, the torque motor receives an input current signal, and under the action of electromagnetic force, the baffle 19 is offset towards the nozzle oil inlet and return control chambers. The pressure in the nozzle oil return control chamber gradually increases, and the pressure in the nozzle oil inlet control chamber gradually decreases, causing the force on the valve core oil inlet control chamber to be greater than the force on the valve core end face. When the force on the end face of the valve core is less than the force on the end face of the valve core return oil control chamber, the valve core moves towards the sleeve end. The return oil pressure hole R of the valve core gradually closes, and the brake pressure hole S gradually opens. The pressure oil connects to the brake pressure hole S through the inlet pressure hole P, and the brake pressure gradually increases until the control force and feedback force acting on the valve core are balanced. The brake pressure hole S maintains a certain opening and outputs a constant brake pressure, i.e., the braking state. When the input current is cut off, the baffle 19 returns to the initial position. The pressure of the nozzle inlet oil control chamber C3 is greater than the pressure of the nozzle return oil control chamber C4, making the force on the end face of the valve core inlet oil control chamber greater than the force on the end face of the valve core return oil control chamber. Therefore, the valve core is pushed to the valve sleeve blockage end position, the brake pressure hole S and the return oil hole R are connected, there is no braking force, and it returns to the non-braking state.

Claims

1. A spool valve assembly for a pressure servo valve, characterized in that, Includes valve core (1), valve sleeve (2), valve body (3), valve sleeve plug (4), return oil end cap (6), valve core return oil control chamber (8), valve core inlet oil control chamber (9), butterfly spring (10), bushing (11), inlet oil end cap (13), and bushing (14); wherein: The valve core is located inside the valve body, and a valve sleeve is fitted on the outer circumferential surface of the valve core; a bushing is between the outer circumferential surface of the valve core at the oil inlet end and the inner circumferential surface of the valve sleeve, and the positioning plate of the bushing end face is in contact with the end face of the valve sleeve; the bushing is located at the oil inlet end of the valve core, and the inner end face of the butterfly spring (10) located in the bushing is in contact with the outer end face of the bushing; thus, a valve core oil inlet control cavity (9) is formed between the inner end face of the bushing and the oil inlet end face of the valve core, and the length between the small end face of the bushing and the oil inlet end face of the valve core is 2.15mm; the oil inlet end cap (13) is fitted on the outer circumferential surface of the bushing (11), thereby securing the bushing; a valve sleeve plug (4) is located on the oil return end face of the valve core, and a gap is formed between the inner end face of the valve sleeve plug and the adjacent valve core end face, which forms the valve core oil return control cavity (8). The nozzle oil inlet control chamber is formed by the space between one end face of the valve sleeve, the inner end face of the oil inlet end cover (13), and the valve body oil chamber. The oil in the valve body chamber is introduced into the valve core oil inlet control chamber (9) through the nozzle oil inlet control chamber. The nozzle oil return control chamber is formed by the other end face of the valve sleeve and the valve body oil chamber. The oil in the valve body chamber is introduced into the valve core oil return control chamber. During the operation of the pressure servo valve, the working state of the slide valve assembly is as follows: When oil is supplied to the pressure servo valve, the oil inlet is divided into two paths, one for the motor pre-stage and the other for the slide valve stage. The oil in the motor pre-stage is distributed in the nozzle return control chamber and the nozzle inlet control chamber through the nozzle assembly. The oil in the nozzle return control chamber acts on the valve core return control end face through the valve core return control chamber (8), and the oil in the nozzle inlet control chamber acts on the valve core inlet control end face through the valve core inlet control chamber (9). The return oil end cap (6) is located on the outer end face of the valve sleeve blockage; the inlet pressure hole P, return oil pressure hole R and brake pressure hole S on the slide valve assembly are distributed on the valve sleeve.

2. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, The valve core (1) has an annular groove with a length of 2.1 mm and a diameter of 5.8 mm on the circumferential surface near the oil inlet end. The groove has a pressure feedback hole with a diameter of 1 mm, which leads to the middle of the valve core to form a pressure feedback chamber for closed-loop control of brake pressure. The middle of the valve core has an annular groove with a length of 11.8 mm and a depth of 1.55 mm. The cavity between the groove and the inner surface of the valve sleeve (2) forms a brake chamber C1 for brake pressure output. The valve core also has an annular groove with a length of 1.5 mm and a diameter of 4.2 mm on the circumferential surface near the oil return end. The cavity between the groove and the inner surface of the valve sleeve forms a return chamber for return pressure output. There are pressure equalization grooves on the circumferential surfaces at both ends of the valve core to prevent valve core jamming caused by uneven pressure. The outer circumferential surface of the oil inlet end of the valve core is stepped, and the height difference of the step is the same as the thickness of the bushing shell.

3. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, The oil inlet pressure hole P on the spool valve assembly is close to the oil inlet end of the valve core, and the oil return pressure hole R is close to the oil return end of the valve core; the brake pressure hole S is located between the oil inlet pressure hole and the oil return pressure hole, in the middle of the valve sleeve axial direction; the opening of the oil inlet pressure hole P is opened in the groove on the outer circumferential surface of the valve sleeve, forming an oil inlet chamber at the opening of the oil inlet pressure hole P; the opening of the oil return pressure hole R is also opened in the groove on the outer circumferential surface of the valve sleeve, forming an oil return chamber at the opening of the oil return pressure hole R; the position of the brake pressure hole S corresponds to the groove on the middle circumferential surface of the valve sleeve.

4. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, The inner diameter of the bushing (14) is the same as the outer diameter of the valve core at the oil inlet end. The outer diameter of the bushing is the same as the inner diameter of the valve sleeve. When the bushing is installed on the valve core, the two are fitted with a clearance. There is a radially protruding positioning plate on the outer end face of the bushing. The outer diameter of the positioning plate is slightly smaller than the diameter at the end of the oil inlet control chamber of the valve sleeve.

5. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, The oil inlet end cap (13) is plate-shaped; there is an axial sleeve on the inner end face of the oil inlet end cap, forming an oil inlet end cap sleeve; the axial length of the oil inlet end cap sleeve is slightly greater than the length of the bushing, but less than the sum of the lengths of the bushing and the bushing washer, and is used to install the bushing and the bushing washer.

6. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, After the valve sleeve is plugged (4) and the sealing ring (7) and the protective ring (5) are installed, it is in clearance fit with the valve body; the valve core (1) and the valve sleeve (2) are ground and matched, and the matching clearance is 0.001~0.003; the bushing and the valve core have a matching clearance of 0.002~0.004; the bushing (14) and the valve sleeve are ground and matched again, and the matching clearance is 0.001~0.003; after the sealing ring (7) is installed on the valve sleeve, it is in clearance fit with the valve body (3).

7. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, When the aircraft is in a non-braking control state, the servo valve torque motor has no input current signal, the baffle (17) is biased towards the nozzle oil inlet control chamber and is used as the initial position. The pressure of the nozzle oil inlet control chamber is greater than the pressure of the nozzle oil return control chamber, so that the force of the valve core oil inlet control chamber on the valve core end face is greater than the force of the valve core oil return control chamber on the valve core end face. Therefore, the valve core is pushed to the end of the valve sleeve blockage, the brake pressure hole S and the oil return hole R are connected, there is no braking force, that is, the non-braking state.

8. The spool valve assembly for a pressure servo valve as described in claim 1, characterized in that, When the aircraft is in braking control mode, the torque motor inputs a current signal, and under the action of electromagnetic force, the baffle (17) is offset towards the nozzle oil inlet control chamber and the nozzle oil return control chamber. The pressure in the nozzle oil return control chamber gradually increases, and the pressure in the nozzle oil inlet control chamber gradually decreases, so that the force acting on the end face of the valve core oil inlet control chamber is less than the force on the end face of the valve core oil return control chamber. The valve core moves towards the bushing end, the valve core oil return pressure hole R gradually closes, and the brake pressure hole S gradually opens. The pressure oil is connected to the brake pressure hole S through the oil inlet pressure hole P, and the brake... The vehicle pressure gradually increases until the control force and feedback force acting on the valve core are balanced. The brake pressure hole S maintains a certain opening and outputs a constant brake pressure, i.e., the braking state. When the input current is cut off, the baffle (17) returns to the initial position. The pressure of the nozzle oil inlet control chamber is greater than the pressure of the nozzle oil return control chamber, so that the force on the end face of the valve core oil inlet control chamber is greater than the force on the end face of the valve core oil return control chamber. Therefore, the valve core is pushed to the end of the valve sleeve blockage position, the brake pressure hole S and the oil return hole R are connected, there is no braking force, and it returns to the non-braking state.

Images