Proportional brake valve and control method

Abstract

The application relates to a proportional brake valve and a control method, which comprises a valve body; a main valve cavity is arranged in the valve body; a main valve core is movably arranged in the main valve cavity; the main valve cavity is provided with a P port, a T port and a B port; the P port, the T port and the B port are respectively communicated with corresponding P cavities, T cavities and B cavities; the main valve core is provided with a middle shaft shoulder and a right shaft shoulder arranged at the right side of the middle shaft shoulder; a balance valve cavity is arranged at the tail side of the main valve cavity; a balance valve core is arranged in the balance valve cavity; the left side head end of the balance valve core abuts against the right end head of the tail end of the main valve core; the application has the advantages of reasonable design, compact structure and convenient use.

Description

Technical Field

[0001] This invention relates to a proportional braking valve and a control method thereof. Background Technology

[0002] The power brake valve outputs pressure proportional to the input current. As the brake valve in a full-power braking system, it provides hydraulic power for electric braking systems, anti-skid braking systems, traction control systems, normal braking, and emergency braking after loss of power.

[0003] The electro-hydraulic proportional brake valve body converts the current signal into continuous braking pressure. It includes the valve body with three ports: oil inlet P (connected to the accumulator / pump), working oil port B (connected to the brake), and oil drain port T (connected to the oil tank). The valve core slides axially in the cavity, and the side wall has a normally open side passage, one end of which is connected to port T and the other end is connected to the lower part of the valve core for hydraulic feedback.

[0004] The valve body linearly converts current and pressure; it stabilizes pressure and provides hydraulic feedback self-balancing: the pressure at port B is fed back to the valve core through the side channel / differential diameter, balancing the electromagnetic force and spring force; failure return: when power is cut off, the electromagnetic force disappears, the reset spring pushes the valve core back, and port B switches to port T to release pressure.

[0005] Existing technologies have several problems, including hysteresis and nonlinearity: valve core friction and residual magnetism in the magnetic circuit can cause the same current to correspond to two pressures, leading to jerky movements during low-speed fine-tuning; dynamic response cannot keep up with high-frequency modulation: ABS / EBS requires pressure adjustments several times per second, and the response bandwidth of proportional valves (especially pilot-operated ones) is generally only tens of Hz, which cannot keep up at high frequencies, requiring the cooperation of booster / pressure reducing valves; contamination and jamming: if there are debris (brake pad wear powder, hose debris) in the hydraulic oil in the braking circuit, the valve core may get stuck in the neutral or off-center position, resulting in insufficient braking force or even failure to brake completely. The fitting clearance of proportional valves is smaller than that of ordinary valves, placing higher demands on oil filters. Insufficient pressure relief rate: during emergency braking, the valve core returns to its original position quickly, and residual pressure in the brake cannot be released in the B→T oil relief channel, resulting in dragging braking.

[0006] Traditional brake valves, influenced by hydraulic forces, cannot achieve precise linear proportional control, suffer from hydraulic interference, have complex manufacturing processes, and exhibit slow response. While electro-hydraulic reverse proportional brake valves and control methods provide a complete brake valve system, they consume significant braking energy and have poor feedback. Utilizing the stroke and electromagnetic force of the electromagnetic coil is crucial to improving reliability and performance. One type of electro-hydraulic proportional brake valve suffers from unbalanced braking force and hydraulic interference, preventing the achievement of a truly linear proportional relationship.

[0007] Traditional brake valves employ a pilot valve mounted on the end of the main valve core. The pilot valve, via chamber B, supports the side of the valve chamber, providing reaction force to actuate the main valve core. The problems with this design are: the main valve chamber contains blind holes and through holes, forming a T-shaped channel. This results in high-pressure oil, high internal stress in the main valve, and deformation of the main valve core due to sudden pressure changes. The presence of blind holes necessitates honing and heat treatment, increasing manufacturing difficulty. Furthermore, the pilot valve core requires high-strength, high-hardness materials to reduce wear on the blind hole channel, further complicating manufacturing. Assembly is also challenging, requiring simultaneous, coaxial sealing between the valve body / valve chamber and the main valve core, as well as between the pilot valve and the main valve core's blind holes, significantly increasing the complexity. During operation, uneven wear can lead to internal leakage. Iron filings generated internally cannot be properly discharged, causing blockages. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a proportional braking valve and a control method thereon.

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows: To achieve smooth actuation, a proportional braking valve includes a valve body. A main valve chamber is provided in the valve body; A solid main valve core is movably installed in the main valve chamber; The main valve chamber has a P port, a T port, and a B port; Ports P, T, and B are respectively connected to the corresponding cavities P, T, and B. The main valve core has a central shoulder and a right shoulder located to the right of the central shoulder; A balance valve chamber is provided on the tail side of the main valve chamber; A balance valve core is installed in the balance valve chamber; The left end of the balance valve core abuts against the right end of the main valve core. As the main valve chamber moves, the right shoulder is used to intermittently block the P chamber from the B chamber; The right shoulder is used to intermittently block the T-cavity and B-cavity; The two ends of the balance valve chamber are respectively connected to chamber T and chamber B; The balance valve core blocks chambers T and B.

[0010] As a further improvement to the above technical solution: In order to achieve equal pressure drive, a right annular groove is provided on the left side of the right shaft shoulder, located on the right side of the middle shaft shoulder, so that the cross-sections of the T cavity and the B cavity on both sides of the right shaft shoulder are set with equal areas. A sealing ring is provided on the left side of the left annular groove to block the T cavity from the P cavity; The main valve core has a left annular groove; the central shoulder is on the right side of the left annular groove; the cross-sections of the P cavity and the B cavity on both sides of the central shoulder are set with equal areas. The balance valve core is set with a shaft of equal diameter and is smaller than the outer diameter of the main valve chamber; The main valve chamber head is connected to the T chamber.

[0011] In order to achieve electromagnetic drive and reduce hydraulic interference, a power source is provided on one side of the valve body. A front-end cavity is provided between the main valve chamber and the power source; The main valve core has a central blind hole; The right end of the central blind hole is connected to a right radial through hole for connecting the T-cavity; The central blind hole connects to the front cavity; The push rod of the power source abuts against the end of the main valve core; The top rod reciprocates. The power source uses electromagnets; In order to achieve the functions of buffering and limiting, and to ensure flexible movement, a limiting spring is set in the front cavity, and a limiting gasket is set on the right end of the limiting spring to abut against the end of the main valve core. A limit step is provided on the left side of the front cavity to control the travel distance of the limit gasket, thereby controlling the travel distance of the main valve core; A left-end protrusion is provided on the left end of the main valve core to abut against the top rod; The left end of the central blind hole is located at the center of the left end protrusion; The main valve core is provided with several oblique through holes to connect the central blind hole and the front cavity; On the left end of the valve body, there are several left radial through holes that communicate with the central blind hole; the left radial through holes are located to the left of the sealing ring on the left side of the left annular groove. The left radial through hole has countersinking.

[0012] In order to achieve unidirectional force application, a plug is provided at the right end stop of the valve body; The left stop seal of the plug is located on the right side of the T-cavity; The right end of the plug is sealed within the tail cavity at the right end of the valve body. A threaded plug is installed in the inner cavity at the rear end of the plugging component; The balance valve chamber connects the rear end inner chamber to the T-chamber; A connecting channel is provided on the valve body to connect chamber B and the tail chamber; The tail cavity is connected to the rear inner cavity through the channel of the plug.

[0013] To achieve automatic reset and provide a buffering force, a reset spring is installed inside the T-cavity; The right end of the return spring is accommodated within the accommodating stop of the left stop of the plug.

[0014] To ensure safe overflow and facilitate emergency maintenance, the T-cavity is connected by a process through-hole; The process through-hole is connected to a bypass channel; A one-way valve core is installed between the bypass channel and the process through hole; A flexible top is provided at the port of the bypass channel; A side passage is provided between the bypass channel and the tail cavity.

[0015] In order to achieve the switching of various operating conditions, after the B cavity and the P cavity begin to connect, the right shoulder moves to the right, and the left annular groove and the B cavity form a gradually opening first throttling orifice.

[0016] The right shoulder of the right shaft connects to the right end head via the right shaft portion; When cavity B and cavity T begin to connect, the right shaft moves to the left, and the right shaft and cavity B form a gradually opening second throttling orifice; A right radial through hole is provided on the right side of the shaft. The shaft diameters of the right-side shaft section, the right-side annular groove section, and the left-side annular groove section are the same. After braking, the force F1 of the power source overcomes the spring force F0 of the return spring and the pressure PB of chamber B on the right end S of the balance valve core.

[0017] A control method for a proportional brake valve, based on the aforementioned proportional brake valve, comprising the following steps: Step 1: The power source drives the main valve core to move to the right, which in turn drives the balance valve core to move to the right in sync; the first throttle orifice gradually opens, connecting port P and port B, while port T is cut off; Step 2: When the pressure at port B increases, it pushes the right end of the balance valve core, thereby driving the main valve core to move to the left, which causes the second throttling orifice to open and drives the first throttling orifice to gradually shrink, connecting port T and port B, and cutting off port P, thereby relieving pressure at port B. Step 3: Depressurize port B, reduce the pressure at port B, and drive the main valve core to move to the right. Combined with the spring force F0 of the return spring, repeat steps 2 and 1 until the pressure at port B on the balance valve core is balanced with the force F1 of the power source.

[0018] As a further improvement to the above technical solution: Ports P, T, and B are all in a closed state.

[0019] If the power source suddenly fails, proceed to step 2.

[0020] Compared to traditional brake valves, this invention employs a separate structure of a balanced valve core and a solid main valve core, thus eliminating the need for strict matching between the two valve cores. The absence of an inner bore resolves the issues of heat generation and residual impurities, reducing the need for high machining and assembly precision. Its variable pilot valve directs the valve's action, eliminating the need for high coaxiality between the two components; only reverse thrust is required. This achieves a sealed, separate assembly, resulting in good flowability, excellent cleanliness, and no heat accumulation.

[0021] The brake valve of this invention can be installed remotely, keeping hydraulic line noise away from operators. The direct-acting valve simplifies the design, eliminating the continuous oil flow and small throttling of a pilot valve. Very low leakage allows for a smaller accumulator size for emergency braking after power loss. The low-resistance coil enables maximum pressure output at low input voltage and allows operation in high-temperature environments or for extended continuous use. A manual overriding function provides a means of mechanically opening the valve in the event of a power failure.

[0022] This invention can output pressure in multiple ranges, making it suitable for various configurations of traction control, ABS, hydraulic brake spring release (HASR), and spring brake hydraulic release (SAHR).

[0023] This invention is reasonably designed, low in cost, sturdy and durable, safe and reliable, simple to operate, time-saving and labor-saving, cost-saving, compact in structure and easy to use. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the valve body component of the present invention.

[0025] Figure 2 This is a schematic diagram of the internal structure of the main valve chamber of the present invention.

[0026] Figure 3 This is a schematic diagram of the stress analysis structure of the present invention.

[0027] Figure 4 This is a schematic diagram of the connection structure between port P and port B of the present invention.

[0028] Figure 5 This is a schematic diagram of the B-port pressurization structure of the present invention.

[0029] Figure 6 This is a schematic diagram of the B-port braking structure of the present invention.

[0030] Figure 7 This is a schematic diagram of the main valve core structure of the present invention.

[0031] Figure 8 This is a schematic diagram of the braking pressure-current curve of the present invention.

[0032] The components include: 1. Valve body; 2. Power source; 3. Main valve chamber; 4. Limit spring; 5. Main valve core; 6. Balance valve core; 7. Plug; 8. Threaded plug; 9. Return spring; 10. Connecting channel; 11. Tail end chamber; 12. Rear end chamber; 13. Front end chamber; 14. Push rod; 15. Limit gasket; 16. First throttling orifice; 17. Second throttling orifice; 18. Sealing ring; 19. Process through hole; 2 0. Bypass channel; 21. One-way valve core; 22. Elastic top; 23. Side flow hole; 24. Balance valve chamber; 25. Receiving stop; 26. Right end head; 27. Right shoulder; 28. Left end head; 29. ​​Right annular groove; 30. Left annular groove; 31. Left radial through hole; 32. Countersunk hole; 33. Right radial through hole; 34. Central blind hole; 35. Oblique through hole; 36. Left end protrusion; 37. Central shoulder. Detailed Implementation

[0033] like Figure 1-8 As shown, the proportional brake valve of this embodiment includes a valve body 1; serving as a carrier.

[0034] A main valve chamber 3 is provided in the valve body 1; a main valve core 5 is movably disposed in the main valve chamber 3; The main valve chamber 3 has a P port, a T port, and a B port; Ports P, T, and B are connected to corresponding cavities P, T, and B, respectively; all are basic structures.

[0035] The main valve core 5 has a central shoulder 37 and a right shoulder 27 located to the right of the central shoulder 37; compared with the conventional structure, it achieves both flow guidance and sealing.

[0036] A balance valve chamber 24 is provided on the tail side of the main valve chamber 3 to achieve contact.

[0037] A balance valve core 6 is provided in the balance valve chamber 24; The left head of the balance valve core 6 abuts against the right head 26 of the tail end of the main valve core 5; it adopts a split structure, which simplifies the structure, reduces the processing difficulty, reduces noise, shortens the valve core, thereby reducing the coaxiality requirement of the hole and the core, and increases rigidity.

[0038] As a structural improvement, as the main valve chamber 3 moves, the right shoulder 27 is used to intermittently block the P chamber from the B chamber; Right shoulder 27 is used to intermittently block the T-cavity and B-cavity; The two ends of the balance valve chamber 24 are respectively connected to chamber T and chamber B; The balance valve core 6 blocks the T chamber and the B chamber.

[0039] A right annular groove 29 is provided on the left side of the right shoulder 27, located on the right side of the middle shoulder 37, so that the cross-sections of the T cavity and the B cavity on both sides of the right shoulder 27 are set with equal areas. A sealing ring 18 is provided on the left side of the left annular groove 30 to block the T cavity from the P cavity; The main valve core 5 has a left annular groove 30; a central shoulder 37 is located on the right side of the left annular groove 30; the cross-sections of the P cavity and the B cavity on both sides of the central shoulder 37 are set with equal areas, thereby achieving equal pressure setting.

[0040] The balance valve core 6 is set with a shaft of equal diameter and is smaller than the outer diameter of the main valve chamber 3; thereby reducing the braking area and reducing power consumption.

[0041] The main valve chamber is connected to the T chamber at the 3rd end, thereby balancing the pressure at both ends and releasing pressure.

[0042] A power source 2 is located on one side of the valve body component 1, thereby achieving power drive.

[0043] A front cavity 13 is provided between the main valve chamber 3 and the power source 2; The main valve core 5 has a central blind hole 34, thus enabling flexible movement of the valve core within a limited space.

[0044] The right end of the central blind hole 34 is connected to a right radial through hole 33 for connecting the T cavity; The central blind hole 34 connects to the front cavity 13; The push rod 14 of the power source 2 abuts against the head end of the main valve core 5; Top rod 14 reciprocates; Power source 2 uses electromagnet components; A limiting spring 4 is provided in the front cavity 13, and a limiting gasket 15 is provided on the right end of the limiting spring 4 to abut against the head end of the main valve core 5; when the valve core moves to the left, the sealing section between the central shoulder and the valve cavity is extended and increased, improving the sealing effect and thus better blocking, and the B port and P port are connected.

[0045] A limiting step is provided on the left side of the front cavity 13 to control the travel distance of the limiting gasket 15, thereby controlling the travel distance of the main valve core 5; thus increasing the sealing effect.

[0046] A left-end protrusion 36 is provided at the left end of the main valve core 5 to abut against the top rod 14, thereby forming a stepped surface. The left end of the central blind hole 34 is located at the center of the left-end protrusion 36. The main valve core 5 is provided with several oblique through holes 35, which are used to connect the central blind hole 34 and the front cavity 13. When the electromagnet is de-energized and retracts rapidly, it opens the central hole, thereby increasing the flow rate at the T port and making the response fast. Normally, the flow rate is balanced by the small flow rate through the oblique holes.

[0047] On the left end head 28 of the valve body 1, there are several left radial through holes 31 that communicate with the central blind hole 34; the left radial through holes 31 are located to the left of the sealing ring 18 on the left side of the left annular groove 30; as an improvement, they allow the oil mixed in the valve cavity gap to flow quickly, avoid the oil in the gap from generating pressure resistance, and make the operation flexible.

[0048] The left radial through hole 31 has a countersunk hole 32 to increase the flow area.

[0049] In order to achieve back-end pressure actuation, a plug 7 is provided at the right end stop of valve body 1; The left stop seal of plug 7 is located on the right side of the T cavity; The right end of the plug 7 is sealed in the tail cavity 11 at the right end of the valve body 1; A threaded plug 8 is provided in the inner cavity 12 at the rear end of the plug 7; The balance valve chamber 24 connects the rear end inner chamber 12 and the T chamber; A connecting channel 10 is provided on the valve body 1 to connect the B cavity and the tail cavity 11; The tail cavity 11 is connected to the rear inner cavity 12 through the channel of the plug 7.

[0050] A return spring 9 is installed inside the T-cavity; The right end of the return spring 9 is accommodated in the accommodating stop 25 of the left stop of the plug 7, thereby achieving automatic positioning.

[0051] The T-cavity is connected by a process through-hole 19; Process through hole 19 is connected to bypass channel 20; A one-way valve core 21 is provided between the bypass channel 20 and the process through hole 19; A flexible top 22 is provided at the port of the bypass channel 20; A side passage 23 is provided between the bypass passage 20 and the tail cavity 11.

[0052] When cavity B and cavity P begin to connect, the right shoulder 27 moves to the right, and the left annular groove 30 and cavity B form a gradually opening first throttling orifice 16.

[0053] The right shoulder 27 is connected to the right end head 26 via the right shaft portion 38; When cavity B and cavity T begin to connect, the right shaft 38 moves to the left, and the right shaft 38 and cavity B form a gradually opening second throttling orifice 17. A right radial through hole 33 is provided on the right side shaft portion 38; The right shaft portion 38, the right annular groove portion 29 and the left annular groove portion 30 have the same shaft diameter; After braking, the force F1 of the power source 2 overcomes the spring force F0 of the return spring 9 and the pressure PB of the B chamber on the right end S of the balance valve core 6.

[0054] The control method for the proportional brake valve in this embodiment is based on the proportional brake valve described above; the following steps are performed; Step 1: Power source 2 drives main valve core 5 to move to the right, which in turn drives balance valve core 6 to move to the right in sync; the first throttle orifice 16 gradually opens, connecting port P and port B, and cutting off port T. Step 2: When the pressure at port B increases, it pushes the right end of the balance valve core 6, thereby driving the main valve core 5 to move to the left, which causes the second throttle orifice 17 to open and drives the first throttle orifice 16 to gradually shrink, connecting port T and port B, and cutting off port P, thereby relieving pressure at port B. Step 3: Depressurize port B, reduce the pressure at port B, and drive the main valve core 5 to move to the right. Combined with the spring force F0 of the return spring 9, repeat steps 2 and 1 until the pressure at port B on the balance valve core 6 is balanced with the force F1 of the power source 2.

[0055] Ports P, T, and B are all in a closed state.

[0056] When power source 2 suddenly fails, execute step 2.

[0057] F1 = F0 + PB × S.

[0058] Valve body component 1, power source 2, main valve chamber 3, limit spring 4, main valve core 5, balance valve core 6, plug component 7, threaded plug 8, return spring 9, connecting channel 10, tail cavity 11, rear end inner cavity 12, front end cavity 13, push rod component 14, limit gasket 15, first throttling orifice 16, second throttling orifice 17, sealing ring 18, process through hole 19, bypass channel 20, one-way valve core 21, elastic push head 22, side flow hole 23. Balance valve chamber 24, receiving stop 25, right end head 26, right shoulder 27, left end head 28, right annular groove 29, left annular groove 30, left radial through hole 31, countersunk 32, right radial through hole 33, center blind hole 34, oblique through hole 35, left end protrusion 36, central shoulder 37. This invention employs a split-structure design: the pilot valve core and the main valve core are clearly defined as independent separate parts. This design eliminates the coaxiality requirements during overall machining, reducing processing difficulty. A clever limiting and buffering mechanism: the valve core's stroke is extremely short, with springs used for reset and limiting. The left spring is mainly used for limiting, while the right spring participates in the reset, and the left spring force is greater than the right. Hole function: the two central holes (figure-eight shaped oblique holes) at the left end of the valve core are used to prevent the push rod from clogging, ensuring unobstructed oil passage.

[0059] Static equilibrium formula: The static equilibrium formula for the electromagnet thrust (F1), spring force (F0), pressure at port B (PB), and working area (S) is established: F1 = F0 + PB × S.

[0060] Compared to the previous version, this invention cleverly achieves axial force cancellation: since port B and port T are connected at a set position, the main valve core has no axial thrust in the cross-section and is only subjected to the pressure of the pilot valve core end face.

[0061] In short, this invention is as follows: Pressure build-up and overshoot processes; Initial overshoot phenomenon: At the moment of power-on, the pressure at port B is zero. The electromagnetic force pushes the valve core to the right, causing the oil inlet opening to be too large. The pressure at port B is quickly built up and exceeds the set value.

[0062] Reverse rebound adjustment: When the pressure at port B exceeds the set value (e.g., 10MPa), the reverse force generated by the high-pressure oil is greater than the electromagnetic thrust, pushing the valve core to rebound to the left and closing the oil inlet.

[0063] It features steady-state balance and oscillation convergence: the valve core oscillates at a high frequency and a small amplitude near the set pressure point (response time is about 0.0x seconds). By continuously adjusting the opening size, it eventually stabilizes at a position where port B is neither connected to port P nor port T, thus achieving pressure holding. This solves the problems of rigid transmission structure, poor flexibility, inability to absorb inertial force, and lack of buffering.

[0064] Application scenario description: This valve is mainly used in the braking system of autonomous vehicles, and achieves precise adjustment of braking pressure by the machine through current control.

[0065] This invention fully utilizes the stroke and electromagnetic force of the electromagnetic coil to improve reliability and performance. The brake valve can be installed remotely, keeping hydraulic line noise away from operators.

[0066] The valve core structure of this invention has a basically uniform diameter and adopts a split valve core, thereby avoiding hysteresis and nonlinearity. This invention can respond quickly and dynamically; the valve core end is connected to the return oil, and reverse flushing through the return oil can solve the problem of contamination and jamming. Its pressure relief rate is fast, and the split balance valve achieves flexible buffering and collision avoidance of oil film and liquid resistance, resulting in low noise, short response distance, and no dragging.

[0067] The present invention has been described in detail for the purpose of making the disclosure clearer, and the prior art will not be listed in detail.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. It is obvious to those skilled in the art that multiple technical solutions of the present invention can be combined. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. All technical contents not described in detail in the present invention are well-known technologies.

Claims

1. A proportional braking valve, characterized in that: Including valve body components (1); A main valve chamber (3) is provided in the valve body component (1); A main valve core (5) is movably disposed in the main valve chamber (3); The main valve chamber (3) has a P port, a T port and a B port; Ports P, T, and B are respectively connected to the corresponding cavities P, T, and B. The main valve core (5) has a central shoulder (37) and a right shoulder (27) located to the right of the central shoulder (37); A balance valve chamber (24) is provided on the tail side of the main valve chamber (3); A balance valve core (6) is provided in the balance valve chamber (24); The left head of the balance valve core (6) abuts against the right head (26) of the tail end of the main valve core (5). As the main valve chamber (3) moves, the right shoulder (27) is used to intermittently block the P chamber from the B chamber; The right shoulder (27) is used to intermittently block the T-cavity and B-cavity; The two ends of the balance valve chamber (24) are respectively connected to chamber T and chamber B; The balance valve core (6) blocks the T chamber and the B chamber.

2. The proportional brake valve according to claim 1, characterized in that: The right shoulder (27) is provided with a right annular groove (29) located on the right side of the middle shoulder (37) on the left side, so that the cross-sections of the T cavity and the B cavity on both sides of the right shoulder (27) are set with equal areas; A sealing ring (18) is provided on the left side of the left annular groove (30) to block the T cavity from the P cavity; The main valve core (5) has a left annular groove (30); the central shoulder (37) is on the right side of the left annular groove (30); the cross-sections of the P cavity and the B cavity on both sides of the central shoulder (37) are set with equal areas. The balance valve core (6) is set with a shaft of equal diameter and is smaller than the outer diameter of the main valve chamber (3); The head end of the main valve chamber (3) is connected to the T chamber.

3. The proportional brake valve according to claim 1 or 2, characterized in that: There is a power source (2) on one side of the valve body (1); A front cavity (13) is provided between the main valve chamber (3) and the power source (2); The main valve core (5) has a central blind hole (34); The right end of the central blind hole (34) is connected to a right radial through hole (33) for connecting the T cavity; The central blind hole (34) connects to the front cavity (13); The push rod (14) of the power source (2) abuts against the head end of the main valve core (5); The top rod (14) reciprocates; The power source (2) uses an electromagnet; A limit spring (4) is provided in the front cavity (13), and a limit gasket (15) is provided at the right end of the limit spring (4) to abut against the head end of the main valve core (5). A limit step is provided on the left side of the front cavity (13) to control the travel distance of the limit gasket (15), thereby controlling the travel distance of the main valve core (5); A left-end protrusion (36) is provided at the left end of the main valve core (5) to abut against the top rod (14). The left end of the central blind hole (34) is located at the center of the left end protrusion (36); The main valve core (5) is provided with several oblique through holes (35) for connecting the central blind hole (34) and the front cavity (13). On the left end head (28) of the valve body (1), there are several left radial through holes (31) communicating with the central blind hole (34); the left radial through holes (31) are located to the left of the sealing ring (18) on the left side of the left annular groove (30); The left radial through hole (31) has a countersink (32).

4. The proportional brake valve according to claim 3, characterized in that: A plug (7) is provided at the right end stop of the valve body (1); The left stop seal of the plug (7) is located on the right side of the T cavity; The right end of the plug (7) is sealed in the tail cavity (11) at the right end of the valve body (1); A threaded plug (8) is provided in the inner cavity (12) at the rear end of the plug (7); The balance valve chamber (24) is connected to the rear end inner chamber (12) and the T chamber; A connecting channel (10) is provided on the valve body (1) to connect the B cavity and the tail cavity (11). The tail cavity (11) is connected to the rear end cavity (12) through the channel of the plug (7).

5. The proportional brake valve according to claim 4, characterized in that: A return spring (9) is provided inside the T cavity; The right end of the return spring (9) is accommodated in the accommodating stop (25) of the left stop of the plug (7).

6. The proportional brake valve according to claim 5, characterized in that: The T-cavity is connected by a process through hole (19). The process through hole (19) is connected to the bypass channel (20); A one-way valve core (21) is provided between the bypass channel (20) and the process through hole (19). An elastic head (22) is provided at the port of the bypass channel (20); A side passage (23) is provided between the bypass passage (20) and the tail cavity (11).

7. The proportional braking valve and control method according to claim 6, characterized in that: When cavity B and cavity P begin to connect, the right shoulder (27) moves to the right, and the left annular groove (30) and cavity B form a gradually opening first throttling orifice (16).

8. The proportional braking valve and control method according to claim 7, characterized in that: The right shoulder (27) is connected to the right end head (26) via the right shaft part (38); When cavity B and cavity T begin to connect, the right shaft (38) moves to the left, and the right shaft (38) and cavity B form a gradually opening second throttling orifice (17). A right radial through hole (33) is provided on the right side shaft portion (38); The right-side shaft portion (38), the right-side annular groove portion (29), and the left-side annular groove portion (30) have the same shaft diameter; After braking, the force F1 of the power source (2) overcomes the spring force F0 of the reset spring (9) and the pressure PB of the B cavity on the right end S of the balance valve core (6).

9. A control method for a proportional braking valve, characterized in that: Based on the proportional brake valve described in claim 3; Perform the following steps; Step 1: The power source (2) drives the main valve core (5) to move to the right, which in turn drives the balance valve core (6) to move to the right in sync; the first throttle orifice (16) gradually opens, connecting the P port and the B port, and cutting off the T port; Step 2: When the pressure at port B increases, it pushes the right end of the balance valve core (6), thereby driving the main valve core (5) to move to the left, which causes the second throttling orifice (17) to open and drives the first throttling orifice (16) to gradually shrink, connecting port T and port B, and cutting off port P, thereby causing port B to release pressure. Step 3, the pressure at port B is released, the pressure at port B decreases, and the power source (2) drives the main valve core (5) to move to the right; Combined with the spring force F0 of the return spring (9), repeat steps 2 and 1 until the pressure at port B on the balance valve core (6) is balanced with the force F1 of the power source (2). Ports P, T and B are all in the closed state.

10. The control method for the proportional brake valve according to claim 9, characterized in that: When the power source (2) fails, execute step 2.

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