Hydraulic actuation brake

Abstract

The invention provides a hydraulic actuation brake which comprises a brake shoe assembly, a brake bottom plate assembly, an expander assembly and a brake cylinder assembly which are sequentially connected, a web plate of the brake shoe assembly is connected with an expander of the expander assembly, and the brake cylinder assembly comprises a service brake cavity and a parking brake cavity which are relatively independent. A driving piston capable of moving in the axial direction of the brake cylinder assembly is arranged in the driving brake cavity, a parking piston capable of moving in the axial direction of the brake cylinder assembly is arranged in the parking brake cavity, one end of the driving piston selectively abuts against the parking piston, and the other end of the driving piston abuts against a force increasing mechanism of the expander. A sealing structure is arranged at the end, close to the traveling piston, of the parking piston, the traveling braking cavity and the parking braking cavity are isolated into independent sealing cavities through the sealing structure, the traveling braking cavity is provided with a traveling oil port, and the parking braking cavity is provided with a parking oil port. The defect of serious redundancy of service braking and parking braking equipment in the prior art is overcome, and the braking force and the braking reliability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of brakes, and in particular to a brake actuated by hydraulic pressure. Background Art

[0002] Brakes are an important guarantee for vehicle driving safety, and the reliability of the braking system directly affects driving safety. Among them, drum brakes have been widely used in the heavy-duty commercial vehicle market due to their simple structure, low manufacturing cost, and large braking torque.

[0003] Currently, common brakes in the commercial vehicle field include drum brakes and disc brakes. Disc brakes are difficult to promote and apply on a large scale in the commercial vehicle market due to their high manufacturing cost and complex structure. Drum brakes use an external power device and undergo a series of mechanical power conversions to push the double-sided brake shoes with friction plates outward along a fixed center of a circle to form a friction pair in contact with the brake drum, thereby completing braking. They have the characteristics of simple structure, low manufacturing cost, and large braking torque, and have been widely used in the commercial vehicle market.

[0004] The actuation forms of drum brakes mainly include: pneumatic camshaft type, pneumatic wedge type, and hydraulic cylinder direct actuation.

[0005] Among them, the pneumatic camshaft type and the pneumatic wedge type use an external double-chamber or single-chamber air chamber. When performing service braking, the high-pressure gas pushes the diaphragm in the parking chamber of the double-chamber air chamber to push the parking spring back to release the parking brake, and at the same time pushes the piston rod in the driving chamber to move linearly (the single-chamber air chamber has no parking brake function, so it only needs to push the piston rod in the air chamber to move linearly), so that the camshaft and the wedge produce rotation or linear motion, and the torque generated by the high-pressure gas is amplified by the involute cam or the wedge with a cone angle, and the brake shoe is quickly brought into close contact with the brake drum, thereby generating a larger braking torque to complete the vehicle's service braking; when performing parking braking, the parking brake spring is reset by releasing the air pressure, thereby pushing the piston of the air chamber brake to move linearly, thereby completing the parking brake. Although the braking torque of this structure is large, its power source is an external air pressure pipeline. On the one hand, due to the high air compression rate and easy leakage, it is difficult to meet long-term braking needs and the braking torque is limited, and it cannot meet the requirements of heavy-load conditions. On the other hand, when the air pressure is too low, the parking brake is difficult to release smoothly, which can easily cause brake drag and generate high brake temperature. In severe cases, wheel-side fire accidents may occur.

[0006] The conventional hydraulic cylinder direct actuation structure, by setting hydraulic cylinders at the places where the brake shoes on both sides are far away from the rotation center, pushes the brake shoes to both sides, thereby completing the braking. Although it can solve the problem of pneumatic brakes due to high air compression rate and easy leakage, and solves the problem of brake debonding; it still has the following two inherent problems: on the one hand, due to the influence of the inherent structure of the hydraulic cylinder, it can only use hydraulic pressure to push the piston for reciprocating linear motion, and cannot arrange the parking spring structure, so it does not have the parking brake function (when the vehicle stops, there is no power, so the liquid in the hydraulic cylinder is in a depressurized state, so braking cannot be performed); on the other hand, because the hydraulic cylinder is used to directly push the brake shoe to contact with the brake to form a friction pair for braking, without power amplification, the braking torque is relatively small, which cannot meet the use requirements of large and heavy-loaded vehicles.

[0007] Therefore, the problem faced by the prior art is that the pneumatic brake cannot meet the requirements of long-term driving braking and there is a risk of brake wear, while the conventional hydraulic brake has a small braking torque and no parking brake function.

[0008] In the prior art, the patent authorization announcement number is CN201902483U, and the patent name is a utility model patent for a serial dual-chamber hydraulic brake master cylinder assembly for automobiles. Fig.13As shown, when braking, the driver presses the brake pedal to cause the first piston 12 to be acted upon by a thrust force, and the first piston 12 moves to the left. After the first main leather cup 15 of the first piston 12 covers the first compensation hole 8, the brake fluid in the first brake chamber 17 builds up pressure, and under the action of this pressure and the resistance of the first return spring 16, the second piston 20 is pushed to overcome the resistance of the second return spring 22 and move to the left. When the second main leather cup 21 of the second piston 20 covers the second compensation hole 3, pressure is generated in the second brake chamber 23, and the brake fluid enters the brake wheel cylinder through the fluid outlet 2 and the brake pipeline to brake the vehicle. When the brake is released, the driver releases the brake pedal, and the second piston 20 and the first piston 12 return to their positions under the action of the second return spring 22 and the first return spring 16. A vacuum is formed in the second brake chamber 23 and the first brake chamber 17, and negative pressure is generated. The brake fluid flows into the second brake chamber 23 through the second supply hole 4, the clearance between the second piston 20 and the cylinder wall of the cylinder body 1, and the edge of the second main leather cup 21; the brake fluid flows into the first brake chamber 17 through the first supply hole 9, the clearance between the first piston 12 and the cylinder wall of the cylinder body 1, and the edge of the first main leather cup 15. When the second piston 20 and the first piston 12 are fully returned, the brake fluid in the brake wheel cylinder enters the second and first brake chambers 23 and 17, and then flows back to the reservoir through the second and first compensation holes 3 and 8 and the liquid inlet joint 6 to establish a new balance. As a hydraulic cylinder built into the brake, its structure and oil channel are complex, the braking process is complex to operate, the fluid replenishment is difficult, the braking reliability is low, the brake is prone to failure, and the brake temperature is generated. Moreover, this structure can only realize driving brake or parking brake. If both are required, two sets of identical solutions need to be configured, which leads to serious equipment redundancy and is not conducive to the overall structural space layout. Summary of the invention

[0009] Therefore, the present invention provides a brake actuated by hydraulic pressure, which can overcome the defects of the prior art that the driving brake and the parking brake are designed separately, resulting in serious equipment redundancy and being unfavorable to the overall structural space layout.

[0010] In order to solve the above problems, the present invention provides a hydraulically actuated brake, comprising a brake shoe assembly, a brake base plate assembly, an expander assembly and a brake cylinder assembly connected in sequence, wherein the expander assembly comprises an expander, and the expander is connected to the belly plate of the brake shoe assembly, and the brake cylinder assembly comprises a front housing, and the front housing has a service piston, and the service piston separates the front housing into a service brake chamber and a parking brake chamber, and the parking brake chamber has a parking piston that can move axially along the brake cylinder assembly, one end of the service piston can be selectively abutted against the parking piston, and the other end of the service piston abuts against the force amplification mechanism of the expander, and the parking The piston has a sealing structure at one end close to the service piston, and the sealing structure isolates the service brake chamber from the parking brake chamber to form an independent sealed chamber. The service brake chamber has a service oil port, and the parking brake chamber has a parking oil port. In an initial state, the service brake chamber is not filled with brake oil, and the parking brake chamber is filled with brake oil. When the service brake is applied, the brake oil enters the service brake chamber through the service oil port, and the service oil pushes the service piston to move toward the expander to perform service braking. When the parking brake is applied, the brake oil in the parking brake chamber flows out, and the parking piston pushes the service piston to move toward the expander to perform parking braking.

[0011] In some embodiments, the hydraulically actuated brake also includes a rear housing, the rear housing including a parking screw arranged along the axial center line of the rear housing, a push plate located at one end of the rear housing, a spring arranged between the push plate and the rear housing, one end of the spring abuts against the rear housing, and the other end abuts against the push plate, the annular edge of the push plate abuts against the inner wall of the front housing to seal the parking brake chamber, and in an initial state, the parking brake chamber is filled with brake oil, and the push plate compresses the spring, and when the parking brake is applied, the brake oil flows out, and under the action of the spring force, the push plate moves toward the direction close to the driving piston, thereby driving the parking piston to squeeze the driving piston to move toward the direction close to the expander, thereby achieving parking brake.

[0012] In some embodiments, the parking piston is a Type I parking piston, whose axial cross-section is a T-shaped structure, whose horizontally extending end can be selectively abutted against the driving piston, and whose vertical end is recessed inward away from the driving piston to form a accommodating cavity, and the parking screw is a Type I parking screw, one end of which extends into the accommodating cavity, and the end of the Type I parking screw can selectively abut against the bottom wall of the accommodating cavity, and the push plate is a Type I push plate, and the axial through hole of the Type I push plate has a limiting step on the side close to the Type I parking piston, which is used to limit the Type I parking screw from disengaging from the Type I push plate, and the end of the Type I parking screw away from the Type I parking piston is connected to the rear shell through a thread.

[0013] In some embodiments, the parking piston is a Type II parking piston, the axial cross-section of the Type II parking piston is a T-shaped structure, and its vertical end face abuts against a Type II parking screw. The Type II parking screw is sleeved on a Type II push plate and is threadedly connected. The Type II push plate drives the Type II parking screw to move closer to or away from the Type II parking piston to achieve parking braking and release.

[0014] In some embodiments, the spring is a single parking spring, or a combined parking spring, or a disc spring.

[0015] In some embodiments, the rear housing is a stamped thin-walled part, or a forged part, or a cast part.

[0016] In some embodiments, when the rear shell is a stamped thin-walled part, a tray is further provided at one end of the rear shell away from the driving piston, and the spring is provided between the push plate and the tray, one end of the spring abuts against the push plate, and the other end abuts against the tray.

[0017] In some embodiments, when the rear shell is a stamped thin-walled part, a buckle groove is provided on the outer wall of the rear shell, which is fastened to the buckle on the front shell.

[0018] In some embodiments, when the rear housing is a forged part or a cast part, the rear housing is threadedly connected to the front housing.

[0019] In some embodiments, when the rear housing is a casting or a forging, a hole adapted to the parking screw is provided at one end of the rear housing away from the driving piston, and the hole is a threaded hole or a through hole, and a sealing groove is provided in the through hole.

[0020] The present invention provides a hydraulically actuated brake, which solves the defects of complex structure and low safety factor caused by the built-in brake cylinder assembly by connecting the brake shoe assembly, the brake base plate assembly, the expander assembly and the brake cylinder assembly in sequence, and placing the brake cylinder assembly externally. In addition, the external brake cylinder assembly can realize the switching between a single driving brake mode and a driving and parking integrated brake mode by replacing hydraulic actuating cylinders of different structures to meet the needs of different usage scenarios. A series driving brake chamber and a parking brake chamber are adopted, and the two chambers are independently controlled to realize separate driving brakes, parking brakes, or simultaneous brakes, which can replace central parking, have higher reliability, improve the braking safety factor, and also improve the braking force and braking reliability. Compared with conventional pneumatic drum brakes, the size and structure of the hydraulic actuating cylinder used in the present invention are relatively small, and the types of parts are significantly reduced, thereby effectively reducing the overall weight of the brake; compared with pneumatic drum brakes of the same specification, the braking torque of the present invention can be increased by more than 41%, and the braking torque density can be increased by 58%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a brake actuated by hydraulic pressure according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the structure of a double-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0023] Figure 3 A cross-sectional view of a first dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0024] Figure 4 The hydraulically actuated brake of the embodiment of the present invention Figure 3 A magnified view of part A;

[0025] Figure 5 A cross-sectional view of a second dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0026] Figure 6 A cross-sectional view of a third dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0027] Figure 7 The hydraulically actuated brake of the embodiment of the present invention Figure 6 Enlarged view of middle part B;

[0028] Figure 8 A cross-sectional view of a fourth dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0029] Fig. 9 The hydraulically actuated brake of the embodiment of the present invention Figure 8 Enlarged view of point C in the middle;

[0030] Fig.10 A cross-sectional view of a fifth dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0031] Fig.11 The hydraulically actuated brake of the embodiment of the present invention Fig.10 Enlarged view of point D in the middle;

[0032] Fig.12 A cross-sectional view of a sixth dual-chamber brake cylinder assembly of a hydraulically actuated brake according to an embodiment of the present invention;

[0033] Fig.13 As background technology, a schematic diagram of a brake structure in the prior art is mentioned.

[0034] The reference numerals are as follows:

[0035] 1. Brake shoe assembly; 2. Brake base plate assembly; 3. Expander assembly; 4. Brake cylinder assembly; 6. Double-chamber brake cylinder assembly; 61. Two-way exhaust valve; 62. Parking oil plug; 63. Driving oil plug; 64. Driving exhaust nozzle; 65. Parking exhaust nozzle; 66. Buckle groove; 71. Front housing; 72. Type I parking screw; 73. Type I tray; 74. Single parking spring; 75. Type I push plate; 76. Type I parking piston; 77. Driving Piston; 78, O-ring; 79, Type I rear housing; 81, combined sealing ring; 82, parking brake chamber; 83, Type II push plate; 84, Type II tray; 85, Type II parking screw; 86, Type II parking piston; 87, service brake chamber; 88, limit rod; 89, combined parking spring; 91, Type II rear housing; 92, connecting thread; 93, Type III rear housing; 94, Type I parking brake assembly; 95, Type II parking brake assembly. DETAILED DESCRIPTION

[0036] See also Figures 1 to 13As shown, according to an embodiment of the present invention, there is provided a brake actuated by hydraulic pressure, comprising a brake shoe assembly 1, a brake base plate assembly 2, an expander assembly 3 and a brake cylinder assembly 4 connected in sequence, wherein the expander assembly 3 comprises an expander, and the expander is connected to the web of the brake shoe assembly 1, and the brake cylinder assembly 4 comprises a front housing 71, wherein the front housing 71 has a service piston 77, and the service piston 77 separates the front housing 71 into a service brake chamber 87 and a parking brake chamber 82, wherein the parking brake chamber 82 has a parking piston capable of axial movement along the brake cylinder assembly 4, and one end of the service piston 77 can be selectively abutted against the parking piston, and the other end of the service piston 77 abuts against the force amplification mechanism of the expander, and the The end of the parking piston close to the driving piston 77 has a sealing structure, and the sealing structure isolates the driving brake chamber 87 from the parking brake chamber 82 to form an independent sealed chamber. The driving brake chamber 87 has a driving oil port, and the parking brake chamber 82 has a parking oil port. In the initial state, the driving brake chamber 87 is not filled with brake oil, and the parking brake chamber 82 is filled with brake oil. When driving brakes, brake oil enters the driving brake chamber 87 through the driving oil port, and the driving oil pushes the driving piston 77 to move toward the expander to perform driving brakes. When parking brakes, the brake oil in the parking brake chamber 82 flows out, and the parking piston pushes the driving piston 77 to move toward the expander to perform parking brakes. By connecting the brake shoe assembly 1, the brake base plate assembly 2, the expander assembly 3 and the brake cylinder assembly 4 in sequence, and the brake cylinder assembly 4 is external, the defects of complex structure and low safety factor caused by the built-in brake cylinder assembly 4 are solved. And the external brake cylinder assembly 4 can switch between a single driving brake mode and a driving and parking integrated brake mode by replacing hydraulic actuators of different structures to meet the needs of different usage scenarios. A series-type driving brake chamber 87 and a parking brake chamber 82 are adopted, and the two chambers are independently controlled to achieve separate driving brakes, parking brakes, or simultaneous brakes, which can replace central parking, have higher reliability, and improve the braking safety factor. Compared with conventional pneumatic drum brakes, the size and structure of the hydraulic actuator cylinder used in the present invention are relatively small, and the types of parts are significantly reduced, thereby effectively reducing the overall weight of the brake; compared with pneumatic drum brakes of the same specification, the braking torque of the present invention can be increased by more than 41%, and the braking torque density is increased by 58%.

[0037] Specifically, the front housing 71 is also provided with a parking oil plug 62, a driving oil plug 63, a driving exhaust nozzle 64 and a parking exhaust nozzle 65 for the brake oil to enter and exit the driving brake chamber 87 and the parking brake chamber 82. A two-way exhaust valve 61 is provided on the rear housing.

[0038] Specifically, a Y-shaped sealing ring 57 and a plurality of guide rings are provided on the circumference of the driving piston 77 to improve the smoothness of the axial movement of the driving piston 77 .

[0039] Specifically, an O-ring 78 is provided at the connection between the front housing 71 and the rear housing. The front housing 71 and the rear housing are designed separately to facilitate the installation of internal structural components. The front housing 71 and the rear housing are connected by a snap-fit ​​method and sealed with an O-ring 78, which is convenient and efficient to install and has a good sealing effect.

[0040] Specifically, the sealing structure is a combined sealing ring 81 .

[0041] Specifically, the web is connected to the adjusting screw of the expander.

[0042] In a specific embodiment, the brake actuated by hydraulic pressure also includes a rear housing, wherein the rear housing includes a parking screw arranged along the axial center line of the rear housing, a push plate at one end of the rear housing, a spring arranged between the push plate and the rear housing, one end of the spring abuts against the rear housing, and the other end abuts against the push plate, and the annular edge of the push plate abuts against the inner wall of the front housing to seal the parking brake chamber 82. In the initial state, the parking brake chamber 82 is filled with brake oil, and the push plate compresses the spring. When the parking brake is applied, the brake oil flows out, and under the action of the spring elastic force, the push plate moves toward the driving piston 77, thereby driving the parking piston to squeeze the driving piston 77 toward the expander to achieve parking brake. By utilizing the elastic force of the spring to push the push plate sleeved on the parking screw, and then pushing the parking piston, the parking brake is achieved, the structure is simple, the fault anomaly is less, and the braking safety factor is improved.

[0043] In a specific embodiment, the parking piston is a Type I parking piston 76, whose axial cross-section is a T-shaped structure, whose horizontally extending end can be selectively abutted against the driving piston 77, and whose vertical end is recessed inward away from the side of the driving piston 77 to form an accommodating cavity, and the parking screw is a Type I parking screw 72, one end of which extends into the accommodating cavity, and the end of the Type I parking screw 72 can be selectively abutted against the bottom wall of the accommodating cavity, and the push plate is a Type I push plate 75, and the axial through hole of the Type I push plate 75 is close to the side of the Type I parking piston 76. A limiting step is provided for limiting the Type I parking screw 72 from disengaging from the Type I push plate 75, and the end of the Type I parking screw 72 away from the Type I parking piston 76 is connected to the rear shell through a thread.

[0044] Specifically, a type I tray 73 is further provided on one side of the rear housing away from the driving piston 77, and the type I parking screw 72 passes through the type I tray 73 and is threadedly connected thereto to fix the type I parking screw 72. By providing a receiving cavity on the vertical end surface of the type I parking piston 76, the type I parking screw 72 is deeply inserted therein, thereby improving the stability of the type I parking screw 72. In addition, the stroke of the receiving cavity is sufficient to meet the parking brake requirements.

[0045] In a specific embodiment, the parking piston is a type II parking piston 86, the axial cross-section of the type II parking piston 86 is a T-shaped structure, and its vertical end face abuts against the type II parking screw 85. The type II parking screw 85 is sleeved on a type II push plate 83 and is threadedly connected. The type II push plate 83 drives the type II parking screw 85 to move closer to or away from the type II parking piston 86 to achieve parking braking and release.

[0046] Specifically, a type II tray 84 is provided on the side of the rear housing away from the driving piston 77. The type II tray 84 is provided with a through hole, and a sealing groove is provided in the through hole, which is used in conjunction with the type II parking screw 85. The type II tray 84 is fixedly connected to the rear housing by screws. The type II parking piston 86 with a T-shaped structure reduces the concave cavity, reduces the use of sealing components, and improves the parking effect.

[0047] In a specific embodiment, the spring is a single parking spring 74, or a combined parking spring 89, or a disc spring.

[0048] Specifically, when the spring is a combined parking spring 89, a plurality of limit rods 88 for supporting the spring are provided on the push plate, the type I tray 73, and the type II tray 84 to improve the parking braking force.

[0049] Specifically, the single parking spring is installed on the boss of the push plate and the tray, and passes through the parking screw. The combined parking spring 89 generally has 4-6, is used in conjunction with the limit rod, is arranged inside the rear housing, is installed on the limit rod, and the limit rod is embedded and installed on the push plate.

[0050] In a specific embodiment, the rear housing is a stamped thin-walled part, or a forged part, or a cast part.

[0051] In a specific embodiment, when the rear shell is a stamped thin-walled part, a tray is also provided at one end of the rear shell away from the driving piston 77, and the spring is provided between the push plate and the tray, one end of the spring abuts against the push plate, and the other end abuts against the tray.

[0052] In a specific embodiment, when the rear shell is a stamped thin-walled part, a buckle groove 66 is provided on the outer wall of the rear shell, which is fastened to the buckle on the front shell 71 .

[0053] In a specific embodiment, when the rear housing is a forged part or a cast part, the rear housing is threadedly connected to the front housing 71 .

[0054] In a specific embodiment, when the rear housing is a casting or a forging, a hole adapted to the parking screw is provided at one end of the rear housing away from the driving piston 77, and the hole is a threaded hole or a through hole, and a sealing groove is provided in the through hole.

[0055] Specifically, the rear shell can be set to three forms: type I rear shell 79, type II rear shell 91 and type III rear shell 93. Among them, the type I rear shell 79 is a stamped thin-walled part with a thickness of 2-3mm; the outer wall of the type I rear shell 79 is provided with a snap groove 66, which is snap-connected and fastened with the front shell, and the interior is used in conjunction with the type I tray 73 or the type II tray 84. The type II rear shell 91 and the type III rear shell 93 are forged or cast parts with a thickness of 8-10mm; the opening inner hole surface of the type II rear shell 91 and the type III rear shell 93 is provided with a thread, and is fastened with the front shell 71 in the form of a threaded connection; the end face of the type II rear shell 91 is provided with a threaded hole, which is threadedly connected with the type I parking screw 72 and used in conjunction with it; the end face of the type III rear shell 93 is provided with a through hole, which is used in conjunction with the type II parking screw 85, and a sealing groove is provided in the middle of the through hole.

[0056] The braking modes are as follows:

[0057] Service brake: When the vehicle needs to brake during driving, brake oil is injected into the service brake chamber 87 from the service oil port, pushing the service piston 77 to the left, pushing the force-enhancing mechanism in the expander to apply the brake, that is, the service piston pushes the force-enhancing mechanism through the spring or push rod, the brake oil is discharged, the service piston 77 moves to the right and resets, and the brake is released.

[0058] Parking brake: The parking brake chamber 82 in the dual-chamber brake cylinder assembly 6 is normally filled with brake oil. When parking brake is needed, the brake oil is discharged, and under the action of the parking spring force, the push plate and the parking piston are pushed to move, and the parking piston pushes the driving piston 77 to produce braking; when parking needs to be released, brake oil is injected into the parking brake chamber 82 from the parking oil channel. At the same time, the driving piston 77 is reset under the action of the expander spring, pushing the parking piston and the push plate back to their original positions, and the parking brake is released.

[0059] Example 1

[0060] The first type of double-chamber brake cylinder assembly 6 has a type I parking piston 76, a type I push plate 75 with a round table, a type I parking screw 72, a single parking spring 74, and a type I tray 73 arranged inside, and a type I rear shell 79 arranged outside. The front shell 71 of the brake cylinder assembly is snap-connected with the type I rear shell 79, and the type I parking screw 72 and the type I tray 73 are threadedly connected.

[0061] Example 2

[0062] The second type of double-chamber brake cylinder assembly 6 has a type II parking piston 86, a type II push plate 83 without a limit rod mounting hole, a type II parking screw 85, a single parking spring 74, and a type II tray 84 arranged inside, and a type I rear shell 79 arranged outside. The front shell 71 of the brake cylinder assembly is snap-connected with the type I rear shell 79, and the type II parking screw 85 is threadedly connected with the type II push plate 83 without a limit rod mounting hole.

[0063] Example 3

[0064] The third type of double-chamber brake cylinder assembly 6 has a type I parking piston 76, a type I push plate 75 with a limit rod mounting hole, a type I parking screw 72, a combined parking spring 89, a limit rod 88, and a type I tray 73 arranged inside, and a type I rear shell 79 arranged outside. The front shell 71 of the brake cylinder assembly is snap-connected with the type I rear shell 79, and the type I parking screw 72 and the type I tray 73 are threadedly connected.

[0065] Example 4

[0066] The fourth type of double-chamber brake cylinder assembly 6 has a type II parking piston 86, a type II push plate 83 with a limit rod mounting hole, a type II parking screw 85, a combined parking spring 89, a limit rod 88, and a type II tray 84 arranged inside, and a type I rear shell 79 arranged outside. The front shell 71 of the brake cylinder assembly is snap-connected with the type I rear shell 79, and the type II parking screw 85 is threadedly connected with the type II push plate 83 with a limit rod mounting hole.

[0067] Example 5

[0068] The fifth double-chamber brake cylinder assembly 6 has a type I parking piston 76, a type I push plate 75 with a limit rod mounting hole, a type I parking screw 72, a combined parking spring 89, and a limit rod 88 arranged inside, and a type II rear housing 91 arranged outside. The front housing 71 of the brake cylinder assembly and the type II rear housing 91 are threadedly connected, and the type I parking screw 72 and the type II rear housing 91 are connected by a connecting thread 92.

[0069] Example 6

[0070] The sixth double-chamber brake cylinder assembly 6 has a type II parking piston 86, a type II push plate 83 with a limit rod mounting hole, a type II parking screw 85, a combined parking spring 89, and a limit rod 88 arranged inside, and a type III rear housing 93 arranged outside. The front housing 71 of the brake cylinder assembly is threadedly connected to the type III rear housing 93, and the type II parking screw 85 is threadedly connected to the type II push plate 83 with a limit rod mounting hole.

[0071] There are two principles for manual parking release:

[0072] Method 1: For the type I parking brake assembly 94, by unscrewing the nut and the type I parking screw, the type I parking screw pulls the push plate to overcome the parking spring force, and the parking is released.

[0073] Method 2: For the bare screw of the type II parking brake assembly 95, by unscrewing the nut, the type II parking screw releases space and the parking is released. This process is not affected by the parking spring force.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A hydraulically actuated brake, characterized in that: The invention comprises a brake shoe assembly (1), a brake base plate assembly (2), an expander assembly (3) and a brake cylinder assembly (4) which are connected in sequence, wherein the expander assembly (3) comprises an expander which is connected to the web of the brake shoe assembly (1), and the brake cylinder assembly (4) comprises a front housing (71) which has a driving piston (77) therein, wherein the driving piston (77) separates the front housing (71) into a driving brake chamber (87) and a parking brake chamber (82), wherein the parking brake chamber (82) has a parking piston which can move axially along the brake cylinder assembly (4), wherein one end of the driving piston (77) can selectively abut against the parking piston, and the other end of the driving piston (77) abuts against a force amplification mechanism of the expander, wherein the parking piston abuts against the driving piston. A sealing structure is provided near one end of the driving piston (77), wherein the sealing structure isolates the driving brake chamber (87) from the parking brake chamber (82) to form an independent sealed chamber. The driving brake chamber (87) has a driving oil port, and the parking brake chamber (82) has a parking oil port. In an initial state, the driving brake chamber (87) is not filled with brake oil, while the parking brake chamber (82) is filled with brake oil. When driving brake is applied, brake oil enters the driving brake chamber (87) through the driving oil port, and the driving oil pushes the driving piston (77) to move toward the expander to perform driving brake. When parking brake is applied, brake oil in the parking brake chamber (82) flows out, and the parking piston pushes the driving piston (77) to move toward the expander to perform parking brake.

2. The hydraulically actuated brake according to claim 1, characterized in that The rear housing also includes a parking screw arranged along the axial center line of the rear housing, a push plate located at one end of the rear housing, a spring arranged between the push plate and the rear housing, one end of the spring abutting against the rear housing, and the other end of the spring abutting against the push plate, the annular edge of the push plate abutting against the inner wall of the front housing (71) to seal the parking brake chamber (82), in an initial state, the parking brake chamber (82) is filled with brake oil, the push plate compresses the spring, when the parking brake is applied, the brake oil flows out, and under the action of the spring elastic force, the push plate moves toward the driving piston (77), thereby driving the parking piston to squeeze the driving piston (77) to move toward the expander, thereby achieving parking brake.

3. The hydraulically actuated brake according to claim 2, characterized in that The parking piston is a type I parking piston (76) having an axial cross-section of a T-shaped structure, a horizontally extending end thereof being selectively abutted against the driving piston (77), and a vertical end thereof being recessed inwardly away from the driving piston (77) to form a receiving cavity, the parking screw being a type I parking screw (72) having one end thereof extending into the receiving cavity, and an end of the type I parking screw (72) being selectively abutted against a bottom wall of the receiving cavity, the push plate being a type I push plate (75), and a limiting step being provided on a side of an axial through hole of the type I push plate (75) close to the type I parking piston (76) for limiting the type I parking screw (72) from being separated from the type I push plate (75), and an end of the type I parking screw (72) being away from the type I parking piston (76) is connected to the rear housing via a thread.

4. The hydraulically actuated brake according to claim 2, characterized in that: The parking piston is a type II parking piston (86). The axial cross-section of the type II parking piston (86) is a T-shaped structure. Its vertical end face abuts against the type II parking screw (85). The type II parking screw (85) is sleeved on the type II push plate (83) and is connected by a thread. The type II push plate (83) drives the type II parking screw (85) to move toward or away from the type II parking piston (86), thereby realizing parking braking and release.

5. The hydraulically actuated brake according to any one of claims 2 to 4, characterized in that: The spring is a single parking spring (74), or a combined parking spring (89), or a disc spring.

6. The hydraulically actuated brake according to claim 5, characterized in that The rear housing is a stamped thin-walled part, or a forged part, or a cast part.

7. The hydraulically actuated brake according to claim 6, characterized in that When the rear housing is a stamped thin-walled part, a tray is further provided at one end of the rear housing away from the driving piston (77), and the spring is provided between the push plate and the tray, with one end of the spring abutting against the push plate and the other end abutting against the tray.

8. The hydraulically actuated brake according to claim 6, characterized in that When the rear shell is a stamped thin-walled part, a buckle groove (66) is provided on the outer wall of the rear shell, which is fastened to the buckle on the front shell (71).

9. The hydraulically actuated brake according to claim 6, characterized in that When the rear housing is a forged part or a cast part, the rear housing is threadedly connected to the front housing (71).

10. The hydraulically actuated brake according to claim 6, characterized in that When the rear housing is a casting or a forging, a hole adapted to the parking screw is provided at one end of the rear housing away from the driving piston (77), the hole being a threaded hole or a through hole, and a sealing groove is provided in the through hole.

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