Plunger type double-cavity brake master cylinder assembly for all-terrain vehicle

Abstract

The invention discloses a plunger type double-cavity brake master cylinder assembly for an all-terrain vehicle. The main cylinder comprises a cylinder body and two brake piston assembly mechanisms, the two brake piston assembly mechanisms are sequentially connected in the cylinder body in the axial direction to form a multi-stage elastic series piston driving structure, the two brake piston assembly mechanisms are the same in structure, the outer end of the brake piston assembly mechanism close to the outer side in the cylinder body is more protruding, and the outer end of the brake piston assembly mechanism close to the inner side in the cylinder body is larger than the outer end of the brake piston assembly mechanism. And the other end of the push rod is connected with the push rod fork and the pedal. According to the invention, the assembly efficiency and the compactness of the whole cylinder are remarkably improved while the synchronism and reliability of double-cavity braking are ensured, and a non-rigid and bufferable force transmission and automatic compensation mechanism between the connecting rod and the piston as well as between the adjacent pistons is realized.

Description

Technical Field

[0001] This invention belongs to the field of vehicle brake technology and relates to a series dual-chamber brake master cylinder suitable for foot brake assemblies of all-terrain vehicles. Background Technology

[0002] All-Terrain Vehicles (ATVs) are specialized vehicles widely used in off-road, agricultural and forestry operations, and emergency rescue. Their working environments are typically extremely harsh and complex, frequently encountering rugged mountain roads, mud, sand, and other extreme conditions. These complex operating conditions place far higher demands on the reliability, stability, and safety of ATV braking systems than on ordinary passenger vehicles.

[0003] In existing technologies, the brake master cylinders of small and medium displacement all-terrain vehicles mainly take several forms, including single-chamber brake master cylinders and simple plunger-type dual-chamber structures. Among them, single-chamber brake master cylinders are simple in structure and low in cost, but they have the risk of single-point failure. Once a seal inside the brake master cylinder is damaged and leaks, or an external pipeline ruptures, the entire braking system will fail completely, losing all braking force and posing a great safety threat.

[0004] To balance cost and dual-circuit safety requirements, some solutions have emerged in the market that use two independent single-chamber master cylinders connected in parallel or combined through a simple linkage mechanism. However, simple plunger-type dual-chamber structures often suffer from poor synchronization and loose structure. For example, the pushing of the two plunger pistons cannot be guaranteed to be completely synchronized, which may lead to uneven pressure build-up in the two circuits during braking, affecting braking stability. The two independent master cylinders arranged side by side occupy a large space, which is not conducive to compact and integrated design on the space-constrained handlebars of all-terrain vehicles. Moreover, traditional sealing structures are prone to premature wear or seal failure when dealing with the frequent vibrations, impacts, and large temperature changes of all-terrain vehicles, leading to brake fluid leakage or air ingress, causing brake weakness or even brake failure.

[0005] Therefore, the existing technology lacks a brake master cylinder assembly designed for the special operating conditions of all-terrain vehicles. Summary of the Invention

[0006] In order to solve the problems existing in the background art, the purpose of the present invention is to design and provide a plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles, providing a solution to the above-mentioned needs. This brake master cylinder can completely solve the problems of all-terrain vehicles.

[0007] The technical solution adopted in this invention is: The master cylinder includes a cylinder body and two brake piston assemblies. The two brake piston assemblies are axially connected in sequence within the cylinder body to form a multi-stage elastic series piston drive structure. The two brake piston assemblies have the same structure. The outer end of the brake piston assembly in the cylinder body protrudes further and is connected to one end of the piston seat and push rod. The other end of the push rod is connected to the foot pedal.

[0008] Each brake piston assembly includes a piston body, a return spring, a spring limiting seat, and a connecting rod. The spring limiting seat is located near the inner end of the cylinder body, and the piston body is located near the outer end of the cylinder body. The inner end of the piston body near the cylinder body has a piston body recess. The spring limiting seat is elastically connected to the piston body recess of the piston body via the return spring. At the same time, the outer end of the spring limiting seat is connected to the center of the piston body recess of the piston body via the connecting rod.

[0009] Specifically, the inner end of the spring limiting seat is provided with an outer flange, the bottom surface of the piston body concave hole is provided with a central flange, one end of the return spring is connected to the outer flange of the spring limiting seat, the other end of the return spring is connected to the bottom surface of the piston body concave hole around the central flange, and the return spring is sleeved outside the spring limiting seat and the connecting rod to form an elastic connection.

[0010] The cross-section of the spring limiting seat is mainly trapezoidal with an outward convex end. The central flange of the concave hole of the piston body has a central threaded hole. One end of the connecting rod is axially and movably limited to the outer end of the spring limiting seat through a step limiting. The other end of the connecting rod passes through the outer end of the spring limiting seat and is threaded into the central threaded hole, so that the axial connection length between the piston body and the spring limiting seat is limited.

[0011] The piston body has a groove at its outer end for connecting the spring limit seat or piston seat of the brake piston assembly mechanism.

[0012] The piston body of the brake piston assembly mechanism is a plunger-type piston.

[0013] The inner end of the spring mounting seat contacts the bottom of the cylinder or the outer end of the piston body, and the outer end is provided with a connecting hole.

[0014] The outer end of the spring limiting seat has a connecting hole for the connecting rod to pass through, and the inner end of the connecting rod has a flange portion with a diameter larger than that of the connecting hole, so that when the connecting rod passes through the connecting hole, the flange portion of the connecting rod is limited within the spring limiting seat.

[0015] The connecting hole of the spring mounting seat includes an assembly part and a positioning part located on the same end face and communicating with each other. The assembly part is located at the center of the end face of the spring mounting seat and is coaxial with the cylinder / brake piston assembly mechanism. The connecting rod is provided with a threaded part. The threaded part of the connecting rod is connected to the central threaded hole of the piston body by thread and is engaged in the positioning part of the connecting hole of the spring mounting seat, thereby restricting the axial movement of the connecting rod.

[0016] The piston body has a hollow groove at its left end, which serves as a recessed hole. Inside the groove is a trapezoidal central protrusion with a threaded hole at the protrusion. The bottom surface of the groove at the right end is a flat end face. The hollow groove at the left end of the piston body can accommodate and fix the second return spring, saving space. The threaded hole at the protrusion connects to the connecting rod. The flat end face on the right side abuts against the spring seat of the first brake piston assembly, smoothly connecting the two brake mechanism assemblies.

[0017] The end of the spring mounting seat is provided with an outwardly extending flange. The inner end face of the outwardly extending flange abuts against the bottom of the cylinder bore or the piston end face. The outer end stepped surface of the flange fixes the return spring. The cap-shaped protrusion is hollow and has a mounting hole in the center for snap-fit ​​installation with the connecting rod.

[0018] The outer flange on the left end face of the connecting rod engages with the mounting hole of the spring mounting seat, and the threaded portion connects with the piston mounting hole. The return spring is sleeved on the mounting seat and the connecting rod, and is built into the plunger-type piston, effectively preventing bending and saving assembly space.

[0019] The two brake piston assemblies are divided into a first brake piston assembly and a second brake piston assembly. The first brake piston assembly is closer to the outer end of the cylinder body, and the second brake piston assembly is closer to the inner end of the cylinder body. The inner end of the first spring limiting seat (51) of the first brake piston assembly is connected to the inner end face of the cylinder body in the axial direction. The outer end of the first piston body (54) of the first brake piston assembly is connected to the second spring limiting seat (21) of the second brake piston assembly. The outer end of the second piston body (24) is connected to the piston seat, so that the first brake piston assembly and the second brake piston assembly are directly connected in a coaxial elastic series through their respective components.

[0020] The main cylinder of this invention is provided with a two-stage piston assembly. Each piston in the two-stage piston assembly has two or more contact points or contact bands that serve a guiding function between it and the main cylinder body. Specifically, an axial guide groove is provided on the inner wall of the main cylinder to ensure brake fluid compensation and pressure relief. The main and auxiliary piston cups are arranged in the circumferential groove. Multiple radial contact points or contact bands guide the two return springs to the plunger-type pistons, effectively preventing the return springs from bending or deforming.

[0021] The second brake piston assembly has a spring mounting seat for the first piston assembly on its right piston end face. This mounting seat is designed as a cap-shaped structure. The brake master cylinder body, the second brake piston assembly, and the first brake piston assembly are connected together via two spring mounting seats. This structure allows for easy assembly of the brake master cylinder by simply inserting the connecting rod into the spring mounting seat and connecting it to the threaded hole of the plunger piston.

[0022] In this invention, the spring seat flange abuts against the bottom of the cylinder bore, and the return spring is sleeved on the spring seat and the connecting rod. The spring seat provides support and prevents the spring from bending during braking.

[0023] The connecting rod head engages with the spring seat mounting hole, and the rod tail connects to the corresponding plunger-type piston mounting hole via a thread. The hollow groove on the left side of the second piston accommodates and secures the second return spring, saving space. The threaded hole at the protrusion connects to the connecting rod. When the piston reaches its full stroke, the spring is completely compressed inside the piston, thus achieving the excellent characteristics of a short axial dimension and a long effective braking stroke in the master cylinder assembly.

[0024] The outer end face of the second piston is a flat end face that abuts against the spring seat of the first brake piston assembly, smoothly connecting the two brake mechanism assemblies. The outer end face of the first piston is installed with the piston seat, and the piston seat is connected to the push rod to avoid wear on the push rod ball joint.

[0025] The beneficial effects of this invention are: This invention, through the connection structure of the cap-shaped spring seat and the connecting rod, and the radial guiding design of the plunger piston, significantly improves assembly efficiency and overall cylinder compactness while ensuring the synchronization and reliability of dual-chamber braking. It is especially suitable for all-terrain vehicles that have high reliability, easy maintenance and strict space constraints in their braking systems.

[0026] This invention achieves a non-rigid, buffered force transmission and automatic compensation mechanism between the connecting rod and the piston, as well as between adjacent pistons, through a return spring set around the periphery of the connecting rod.

[0027] This invention enables true dual-circuit safety braking within a limited installation space, while possessing high reliability, excellent synchronization performance, low overall cost, and good handling feel, thus overcoming various defects in existing technologies and better meeting the special usage needs of all-terrain vehicles. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the brake master cylinder of the present invention; Figure 2This is a schematic diagram of the first piston assembly structure of the present invention; Figure 3 This is a schematic diagram of the second piston assembly structure of the present invention; Figure 4 This is a schematic diagram of the brake piston of the present invention.

[0029] In the diagram: 1. Cylinder block, 2. Second brake piston assembly, 3. Main piston cup, 4. Secondary piston cup, 5. First brake piston assembly, 6. Main piston cup, 7. Secondary piston cup, 8. Piston seat, 9. Push rod; Second piston body (24), second return spring (23), second spring limit seat (21), and second connecting rod (22); The components include a first piston body (54), a first return spring (53), a first spring limit seat (51), and a first connecting rod (52). Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] This invention provides a plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles, such as... Figure 1 As shown, it mainly includes the brake master cylinder body 1, the first piston assembly 5, the second piston assembly 2, the push rod 9, and various sealing components.

[0032] like Figure 1 As shown, the master cylinder includes a cylinder body 1 and two brake piston assemblies. The cylinder body 1 has two chambers, each housing a brake piston assembly. The two chambers are coaxially arranged and directly connected. The two brake piston assemblies are axially connected in series within the cylinder body 1 to form a multi-stage elastic series piston drive structure. The two brake piston assemblies have basically the same structure. The outermost brake piston assembly in the cylinder body 1 has a more protruding outer end, which is connected to one end of a piston seat 8 and a push rod 9. The other end of the push rod 9 is connected to the foot pedal.

[0033] The brake master cylinder body 1 has a series of through-hole structures. The first piston assembly and the second piston assembly are arranged in series inside the brake master cylinder body 1. The first piston assembly 5, together with the main piston cup 6, the auxiliary piston cup 7 and the inner wall of the brake master cylinder body 1, radially seals and together forms the first hydraulic chamber; the second piston assembly 2, together with the main piston cup 3, the auxiliary piston cup 4 and the inner wall of the brake master cylinder body 1, radially seals and together forms an independent second hydraulic chamber, thereby realizing a series dual-circuit safety braking.

[0034] This invention employs a multi-stage elastic series piston drive structure. Through springs arranged around the connecting rod, a non-rigid, buffered force transmission and automatic compensation mechanism is achieved between the connecting rod and the piston, as well as between adjacent pistons.

[0035] Specifically, such as Figure 1 As shown, the piston body has a hollow groove at its left end, which serves as a recessed hole. A central protrusion is located within the groove, and a threaded hole is located at the central protrusion. The bottom surface of the groove at the right end is a flat end face. The hollow groove at the left end of the piston body can accommodate and fix the second return spring, saving space. The threaded hole at the protrusion connects to the connecting rod. The flat end face on the right side abuts against the spring seat of the first brake piston assembly, smoothly connecting the two brake mechanism assemblies.

[0036] Specifically, such as Figure 1 As shown, the end of the spring mounting seat is provided with an outwardly extending flange. The inner end face of the outwardly extending flange abuts against the bottom of the cylinder bore or the piston end face. The outer end stepped surface of the flange fixes the return spring. The cap-shaped protrusion is hollow and has a mounting hole in the center, which is snapped into the connecting rod for installation.

[0037] Specifically, such as Figure 1 As shown, the outer flange on the left end face of the connecting rod engages with the mounting hole of the spring mounting seat, and the threaded portion connects with the piston mounting hole. The return spring is sleeved on the mounting seat and the connecting rod, and is built into the plunger-type piston, effectively preventing bending and saving assembly space.

[0038] The two brake piston assemblies are divided into a first brake piston assembly 5 and a second brake piston assembly 2. The first brake piston assembly is closer to the inner end of the cylinder 1, and the second brake piston assembly is closer to the outer end of the cylinder 1. The inner end of the first spring limiting seat 51 of the first brake piston assembly 5 is connected to the inner end face of the cylinder 1 in the axial direction. The outer end of the first piston body 54 of the first brake piston assembly 5 is connected to the second spring limiting seat 21 of the second brake piston assembly 2. The outer end of the second piston body 24 is connected to the piston seat 8, so that the first brake piston assembly 5 and the second brake piston assembly 2 are directly and coaxially elastically connected in series through their respective components.

[0039] like Figure 3 As shown, the first brake piston assembly mechanism 5 specifically implemented includes a first piston body 54, a first return spring 53, a first spring limiting seat 51, and a first connecting rod 52. The inner end of the first spring limiting seat 51 is connected to the inner end face of the cylinder body 1 in the axial direction. The inner end of the first piston body 54 near the cylinder body 1 is provided with a first piston body recess 541. The first spring limiting seat 51 is elastically connected to the first piston body recess 541 of the first piston body 54 after passing through the first return spring 53. At the same time, the outer end of the first spring limiting seat 51 is connected to the inner center of the first piston body recess 541 of the first piston body 54 through the first connecting rod 52. The outer end of the first piston body 54 is connected to the second spring limiting seat 21 of the second brake piston assembly mechanism 2.

[0040] like Figure 4As shown, specifically, the inner end of the first spring limiting seat 51 is provided with an outer flange, the bottom surface of the first piston body concave hole 541 is provided with a central flange 542, one end of the first return spring 53 is connected to the outer flange of the first spring limiting seat 51, and the other end of the first return spring 53 is connected to the bottom surface of the first piston body concave hole 541 around the central flange 542. The first return spring 53 is sleeved outside the first spring limiting seat 51 and the first connecting rod 52 to form an elastic connection.

[0041] The cross-section of the first spring limiting seat 51 is mainly trapezoidal with an outward protrusion. The central flange 542 of the first piston body concave hole 541 is provided with a central threaded hole 543. The inner end of the first connecting rod 52 is axially and movably limited to the outer end of the first spring limiting seat 51 by a step limiting. After the outer end of the first connecting rod 52 passes through the outer end of the first spring limiting seat 51, it is threaded into the central threaded hole 543, so that the axial connection length between the first piston body 54 and the first spring limiting seat 51 is limited.

[0042] The outer end of the first piston body 54 is provided with a groove for connecting the second spring limit seat 21 of the second brake piston assembly mechanism 2.

[0043] The outer end of the first spring limiting seat 51 is opened in the connecting hole through which the first connecting rod 52 passes. The inner end of the first connecting rod 52 is provided with a flange portion. The diameter of the flange portion is larger than the diameter of the connecting hole, so that when the first connecting rod 52 passes through the connecting hole, the flange portion of the first connecting rod 52 is limited within the first spring limiting seat 51.

[0044] like Figure 2 As shown, the second brake piston assembly mechanism 2 includes a second piston body 24, a second return spring 23, a second spring limiting seat 21, and a second connecting rod 22. The inner end of the second spring limiting seat 21 is connected to the outer end of the first piston body 54 of the first brake piston assembly mechanism 5. The inner end of the second piston body 24 near the cylinder 1 is provided with a second piston body recess. The second spring limiting seat 21 is elastically connected to the second piston body recess of the second piston body 24 via the second return spring 23. At the same time, the outer end of the second spring limiting seat 21 is connected to the center of the second piston body recess of the second piston body 24 via the second connecting rod 22. The outer end of the second piston body 24 is connected to the piston seat 8.

[0045] Specifically, the inner end of the second spring limiting seat 21 is provided with an outer flange, the bottom surface of the second piston body concave hole is provided with a central flange, one end of the second return spring 23 is connected to the outer flange of the second spring limiting seat 21, the other end of the second return spring 23 is connected to the bottom surface of the second piston body concave hole around the central flange, and the second return spring 23 is sleeved outside the second spring limiting seat 21 and the second connecting rod 22 to form an elastic connection.

[0046] The cross-section of the second spring limiting seat 21 is mainly a trapezoidal shape that bulges outward. The central flange of the concave hole of the second piston body has a central threaded hole. One end of the second connecting rod 22 is axially and movably limited to the outer end of the second spring limiting seat 21 through a step limiting. The other end of the second connecting rod 22 passes through the outer end of the second spring limiting seat 21 and is threaded into the central threaded hole, so that the axial connection length between the second piston body 24 and the second spring limiting seat 21 is limited.

[0047] The outer end of the second piston body 24 has a groove for connecting and accommodating the piston seat 8.

[0048] The outer end of the second spring limiting seat 21 is opened in the connecting hole through which the second connecting rod 22 passes. The inner end of the second connecting rod 22 is provided with a flange portion. The diameter of the flange portion is larger than the diameter of the connecting hole, so that when the second connecting rod 22 passes through the connecting hole, the flange portion of the second connecting rod 22 is limited within the second spring limiting seat 21.

[0049] The first piston body 54 of the first brake piston assembly 5 and the second piston body 24 of the second brake piston assembly 2 are both plunger-type pistons.

[0050] The core of this invention lies in two highly integrated brake piston assemblies.

[0051] In the first piston assembly structure, the first piston body 54 has an integrally formed connecting rod 52. The first connecting rod 52 is engaged in the mounting hole of the first spring limiting seat 51 and connected to the threaded hole 543 of the first piston via threads. The first return spring 53 is pre-tightened and fixed between the recessed hole 541 of the first piston body and the first spring limiting seat 51. This structure not only integrates the piston, spring, and limiting seat into one unit, simplifying assembly, but also more precisely defines the working stroke of the first hydraulic chamber.

[0052] The second piston assembly has the same structure and principle as the first piston assembly. The second return spring 23 is sleeved on the second spring limiting seat 21 and the second connecting rod 22, with its two ends fixed to one side of the flange of the second spring limiting seat 21 and the inside of the plunger-type second piston, respectively, thus precisely limiting the working stroke of the second hydraulic chamber.

[0053] To ensure smooth piston movement and prevent uneven wear under harsh operating conditions, this invention employs a multi-guided design: at least two radial contact points (e.g., ...) are provided between the first piston body 54 and the inner wall of the brake master cylinder 1. Figure 1 At points a and b in the middle, it plays a major guiding role. At least three radial contact points (such as...) are provided between the second piston body 24 and the inner wall of the main cylinder body 1. Figure 1 (At points c, d, and e), more stable support and guidance are provided. Throughout the braking stroke, the contact points between the piston and the cylinder increase, further enhancing the guiding effect and effectively overcoming uneven wear and abnormal noise.

[0054] To achieve a compact main cylinder assembly, this invention employs a two-stage built-in spring design: The first piston 54 has a countersunk hole machined at its rear end, and the first return spring 53 is completely accommodated within the countersunk hole 541 and the spring limiting seat 51. When the piston reaches its full stroke, the spring is completely compressed inside the piston, thereby achieving the excellent characteristics of a short axial dimension and a long effective braking stroke in the master cylinder assembly.

[0055] When the driver depresses the brake pedal of the all-terrain vehicle, the pedal force is amplified by the servo-assisted mechanism and then pushes the first piston assembly to move via push rod 9. Since the spring force of the second return spring is smaller than that of the first return spring, the first piston assembly, after moving as a whole, will first compress the second return spring 53 and establish pressure in the second hydraulic chamber. Simultaneously, through hydraulic or mechanical transmission, the second piston assembly is pushed to move, further compressing the first return spring within the first piston assembly and establishing pressure in the first hydraulic chamber. Two independent hydraulic lines are respectively delivered to the front and rear axle brakes through the oil outlet to achieve braking.

[0056] When the brakes are released, the elastic force of the first and second return springs drives their respective piston assemblies to reset, and brake fluid is replenished into the hydraulic chamber through the inlet / outlet port at the front end of the piston, in preparation for the next braking.

[0057] In summary, this invention creatively provides a plunger-type dual-chamber brake master cylinder assembly that is compact, highly reliable, easy to assemble, and particularly suitable for the harsh working conditions of all-terrain vehicles by integrating an integrated piston assembly, multi-point radial guidance, a compact stroke design with built-in springs, and a push rod quick-connect structure.

Claims

1. A plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles, characterized in that: The master cylinder includes a cylinder body (1) and two brake piston assemblies. The two brake piston assemblies are axially connected in sequence within the cylinder body (1) to form a multi-stage elastic series piston drive structure. The two brake piston assemblies have the same structure. The outer end of one of the brake piston assemblies in the cylinder body (1) protrudes further and is connected to one end of the piston seat (8) and the push rod (9). The other end of the push rod (9) is connected to the foot pedal.

2. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 1, characterized in that: Each brake piston assembly includes a piston body, a return spring, a spring limit seat, and a connecting rod. The spring limit seat is located near the inner end of the cylinder body, and the inner end of the piston body has a piston body recess. The spring limit seat is elastically connected to the piston body recess of the piston body via the return spring. At the same time, the outer end of the spring limit seat is connected to the center of the piston body recess of the piston body via the connecting rod.

3. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 2, characterized in that: The inner end of the spring limiting seat is provided with an outer flange, and the center of the bottom surface of the piston body concave hole is provided with a central flange. One end of the return spring is connected to the outer flange of the spring limiting seat, and the other end of the return spring is connected to the bottom surface of the piston body concave hole around the central flange, forming an elastic connection.

4. The all-terrain vehicle plunger-type dual-chamber brake master cylinder assembly according to claim 2, characterized in that: The piston body has a central threaded hole on its central flange. One end of the connecting rod is axially and movably connected to the outer end of the spring limit seat via a step limit. The other end of the connecting rod passes through the outer end of the spring limit seat and is threaded into the central threaded hole, so that the piston body and the spring limit seat are axially and movably connected.

5. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 2, characterized in that: The piston body has a groove at its outer end for connecting the spring limit seat or piston seat (8) of the brake piston assembly mechanism.

6. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 2, characterized in that: The piston body of the brake piston assembly mechanism is a plunger-type piston.

7. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 1, characterized in that: The inner end of the spring mounting seat contacts the bottom of the cylinder or the outer end of the piston body, and the outer end is provided with a connecting hole.

8. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 7, characterized in that: The outer end of the spring limiting seat has a connecting hole for the connecting rod to pass through, and the inner end of the connecting rod has a flange portion with a diameter larger than that of the connecting hole.

9. The plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 7, characterized in that: The connecting hole of the spring mounting seat includes an assembly part and a positioning part located on the same end face. The assembly part is located at the center of the end face of the spring mounting seat and is coaxial with the cylinder / brake piston assembly mechanism. The connecting rod is provided with a threaded part. The threaded part of the connecting rod is connected to the central threaded hole of the piston body by thread and is engaged in the positioning part of the connecting hole of the spring mounting seat, thereby restricting the axial movement of the connecting rod.

10. A plunger-type dual-chamber brake master cylinder assembly for all-terrain vehicles according to claim 7, characterized in that: The two brake piston assemblies are divided into a first brake piston assembly (5) and a second brake piston assembly (2). The first brake piston assembly (5) is closer to the outer end of the cylinder (1), and the second brake piston assembly (2) is closer to the inner end of the cylinder (1). The inner end of the first spring limiting seat (51) of the first brake piston assembly (5) is connected to the inner end face of the cylinder (1) in the axial direction. The outer end of the first piston body (54) of the first brake piston assembly (5) is connected to the second spring limiting seat (21) of the second brake piston assembly (2). The outer end of the second piston body (24) is connected to the piston seat (8), so that the first brake piston assembly (5) and the second brake piston assembly (2) are directly and elastically connected in series through their respective components.

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