A power brake unit for a brake

Abstract

The application discloses a kind of for brake booster brake device in the technical field of vehicle braking, the first one-way valve of the front variable cavity in cylinder is provided with one-way communication to the oil tank oil port, and the taper shaft sleeve for opening the first one-way valve is set in combination with the plug body, when brake force reaches maximum, the first one-way valve is opened, and the pressure oil in the front variable cavity flows back to the oil tank through the first one-way valve.The first one-way valve is installed on the cylinder, which reduces the difficulty of production assembly and is convenient for maintenance and replacement.A large cavity and a small cavity are provided in the cylinder, the diameter of the large cavity is larger than that of the small cavity, when the first one-way valve is opened, the extrusion force of the piston on the hydraulic oil in the small cavity is multiplied by several times, which achieves good booster braking effect and is suitable for large machinery.

Description

Technical Field

[0001] This invention relates to the field of vehicle braking technology, and more specifically to a power-assisted braking device for braking. Background Technology

[0002] Currently, most vehicle braking systems use hydraulic brakes, which utilize hydraulic oil to transmit braking force. When braking, the piston pushes the pressurized oil in the cylinder into the oil passage of the brake pads, causing the brake pads to approach and press tightly against the brake disc, thus achieving the braking effect.

[0003] The force that drives the piston to move axially within the cylinder comes from the driver's foot pedal force and the pressure from the external oil pump. The hydraulic oil pumped into the space behind the piston exerts a strong forward pressure on the piston, which is the main force driving the piston to move.

[0004] In the aforementioned power-assisted braking device, the pressure generated by the hydraulic oil from the oil pump may be sufficient for small vehicles, but the effect of power-assisted braking on large machinery is not as expected. Furthermore, when the brake pads are in close contact with the brake disc and the braking force reaches its maximum, the aforementioned power-assisted braking device uses a one-way valve installed in the piston to allow the hydraulic oil to flow back to the oil tank. This makes production difficult and makes replacement and maintenance inconvenient. Summary of the Invention

[0005] The purpose of this invention is to provide a power-assisted braking device for braking, in order to solve the technical problem that the pressure formed by the hydraulic oil from the oil pump in the existing power-assisted braking device does not achieve the expected effect of power-assisted braking on large machinery, and the technical problem that when the braking force reaches the maximum, the power-assisted braking device uses a one-way valve set in the piston to make the hydraulic oil flow back to the oil tank, which is difficult to produce and inconvenient to replace and maintain.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides a power-assisted braking device for braking, including a cylinder body. The cylinder body is provided with interconnected small cavities and large cavities distributed along the axial direction. The diameter of the large cavity is larger than the diameter of the small cavity. The cylinder body is provided with an oil tank port connected to an oil tank and an oil pump port connected to an oil pump at positions corresponding to the large cavity. A branch line connected to the large cavity is also provided on the side of the oil tank port near the small cavity, and a first one-way valve that unidirectionally flows to the oil tank port is installed in the branch line. A brake port connected to a brake actuator is provided on the side of the cylinder body away from the small cavity.

[0007] A piston is installed inside the cylinder, and the piston head is located inside the small cavity. A piston head sealing ring is installed on the outer wall of the piston head. A front variable cavity and a rear variable cavity are formed between the piston body at its front and rear ends and the cylinder body, respectively. A hole is provided inside the piston head to connect the small cavity and the front variable cavity, and a second one-way valve is provided inside the hole to unidirectionally guide the small cavity.

[0008] The piston is provided with a reversing valve core, and the center of the reversing valve core is provided with a valve core cavity that communicates with the rear variable cavity. Both the reversing valve core and the piston are provided with oil ports and sealing rings. The reversing valve core can move axially to control the rear variable cavity to communicate with the oil pump port, so that the oil pump assists the piston to move and provides braking assistance, or the rear variable cavity to communicate with the oil tank port, so that the pressure oil in the rear variable cavity flows back to the oil tank to relieve pressure.

[0009] The piston can move towards the front variable cavity to block the connection between the oil tank port and the front variable cavity, and force the pressure oil in the front variable cavity into the small cavity, so that the brake pads are close to the brake disc; the plug body is fitted with a conical bushing for opening the first one-way valve at one end of the front variable cavity, so that when the piston reaches the maximum braking force, the pressure oil in the front variable cavity flows back to the oil tank through the first one-way valve.

[0010] As a preferred embodiment of the present invention, the piston outer edge is provided with a first piston oil port, a first piston sealing ring, a second piston oil port, a second piston sealing ring, a third piston oil port, and a third piston sealing ring in sequence in the direction away from the small cavity. Each piston sealing ring is installed on the outward protruding ring of the piston and is in close contact with the inner wall of the cylinder. Each piston oil port is used to connect the large cavity and the piston inner cavity. The third piston sealing ring and the tail end of the cylinder form the rear variable cavity.

[0011] The piston cavity is provided with a reversing valve core that can move axially. The end of the reversing valve core away from the small cavity passes through the tail end of the cylinder body and is sealed to the cylinder body by a fourth valve core sealing ring. The reversing valve core is provided with a first valve core sealing ring, a first valve core oil port, a second valve core sealing ring, a third valve core sealing ring, a second valve core oil port, and a third valve core oil port in sequence along the direction away from the small cavity. The third valve core oil port is connected to the rear variable cavity.

[0012] As a preferred embodiment of the present invention, a piston spring is provided inside the front variable cavity and outside the piston. One end of the piston spring is sleeved on the plug body, and the other end is sleeved on a positioning ring that extends in the direction of the large cavity from the separation surface of the large cavity and the small cavity. The tapered bushing is displaced outside the piston spring.

[0013] The positioning ring is provided with a positioning ring oil port for connecting the large cavity and the small cavity;

[0014] A reversing spring is provided between the end of the reversing valve core near the small cavity and the piston.

[0015] As a preferred embodiment of the present invention, a neck is further provided between the plug head and the plug body, the diameter of the neck being smaller than the diameter of the plug head and the diameter of the small cavity, and a channel connecting the front variable cavity and the small cavity is provided on the neck.

[0016] As a preferred embodiment of the present invention, an exhaust port is provided on the cylinder body at the position corresponding to the small cavity, and a vent plug is installed in the exhaust port. Both the vent plug and the exhaust port are stepped, and a sealing ring is provided on the outer side of the smaller diameter end of the vent plug.

[0017] As a preferred embodiment of the present invention, the first one-way valve includes a valve core whose head extends into the large cavity, a compression spring located at the tail of the valve core, and a sealing valve stem threaded onto the cylinder body for constraining the compression spring.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] This invention features a first one-way valve on the cylinder block, providing unidirectional flow from the front variable cavity to the oil tank port. Combined with a conical sleeve on the plug body for opening the first one-way valve, when the braking force reaches its maximum, the first one-way valve is opened, allowing the pressurized oil in the front variable cavity to flow back to the oil tank through the first one-way valve. The first one-way valve's installation on the cylinder block reduces manufacturing and assembly difficulty and facilitates maintenance and replacement.

[0020] The cylinder is equipped with a large chamber and a small chamber, with the diameter of the large chamber being larger than that of the small chamber. When the first check valve is opened, the piston can exert a multiplied pressure on the hydraulic oil in the small chamber, resulting in a good power-assisted braking effect, which is suitable for large machinery. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the braking device in its initial state according to an embodiment of the present invention;

[0023] Figure 2This is a schematic diagram of the braking device, brake disc, and caliper in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of the reversing valve core when it has just moved to the left end of the piston in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of the first piston sealing ring when it is about to block the oil tank port in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the structure of the first piston sealing ring when it passes the oil tank port in an embodiment of the present invention;

[0027] Figure 6 This is a theoretical model for unassisted braking.

[0028] Figure 7 This is a schematic diagram of the structure when the tapered bushing just touches the first one-way valve in an embodiment of the present invention;

[0029] Figure 8 This is a schematic diagram of the structure when the conical bushing opens the first one-way valve in an embodiment of the present invention;

[0030] Figure 9 Theoretical model for assisted braking;

[0031] Figure 10 This is a schematic diagram of the structure when the piston moves to the leftmost end in an embodiment of the present invention;

[0032] Figure 11 This is a schematic diagram of the structure when the piston moves to the leftmost end and the reversing valve core resets to the right in an embodiment of the present invention.

[0033] The labels in the diagram represent the following:

[0034] 1-Cylinder block, 2-Small chamber, 3-Large chamber, 4-Fuel tank port, 5-Fuel pump port, 6-Branch, 7-First check valve, 8-Brake port, 9-Piston, 10-Front variable chamber, 11-Rear variable chamber, 12-Second check valve, 13-Directional control valve core, 14-Valve core inner cavity, 15-Conical bushing, 16-First piston port, 17-First piston seal, 18-Second piston port, 19-Second piston seal, 20-Third piston 21-Third piston seal ring, 22-Raised ring, 23-Fourth valve core seal ring, 24-First valve core seal ring, 25-First valve core oil port, 26-Second valve core seal ring, 27-Third valve core seal ring, 28-Second valve core oil port, 29-Third valve core oil port, 30-Piston spring, 31-Positioning ring, 32-Positioning ring oil port, 33-Reversing spring, 34-Plug head, 35-Plug body, 36-Plug neck, 37-Vent plug. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention specifically provides a power-assisted braking device for braking, comprising a cylinder body 1, wherein the cylinder body 1 is provided with interconnected small chambers 2 and large chambers 3 distributed axially, the diameter of the large chamber 3 being larger than the diameter of the small chamber 2, the cylinder body 1 being provided with an oil tank port 4 connected to an oil tank and an oil pump port 5 connected to an oil pump at positions corresponding to the large chamber 3, the oil tank port 4 being provided with a branch 6 connected to the large chamber 3 on the side near the small chamber 2, and a first one-way valve 7 being installed in the branch 6 for unidirectional flow to the oil tank port 4, and a brake port 8 connected to a brake actuator being provided on the side of the cylinder body 1 away from the small chamber 2;

[0037] A piston 9 is installed inside the cylinder 1. The plug 34 of the piston 9 is located inside the small cavity 2, and a sealing ring is provided on the outer wall of the plug 34. A front variable cavity 10 and a rear variable cavity 11 are formed between the front and rear ends of the plug body 35 of the piston 9 and the cylinder 1, respectively. A hole is provided inside the plug 34 to connect the small cavity 2 and the front variable cavity 10, and a second one-way valve 12 is provided inside the hole to unidirectionally guide the small cavity 2.

[0038] The piston 9 is provided with a reversing valve core 13. The reversing valve core 13 has a valve core inner cavity 14 that communicates with the rear variable cavity 11. Both the reversing valve core 13 and the piston 9 are provided with oil ports and sealing rings. The reversing valve core 13 can move axially to control the rear variable cavity 11 to communicate with the oil pump oil port 5, so that the oil pump assists the piston 9 to move and provide braking assistance, or the rear variable cavity 11 to communicate with the oil tank oil port 4, so that the pressure oil in the rear variable cavity 11 flows back to the oil tank to relieve pressure.

[0039] The piston 9 can move towards the front variable cavity 10 to block the communication between the oil tank port 4 and the front variable cavity 10, and force the pressure oil in the front variable cavity 10 into the small cavity 2, so that the brake pads are close to the brake disc; the plug 35 is provided with a tapered bushing 15 for opening the first one-way valve 7 outside one end of the front variable cavity 10, so that when the braking force reaches the maximum, the pressure oil in the front variable cavity 10 flows back to the oil tank through the first one-way valve 7.

[0040] In summary, this invention provides a first one-way valve 7 on the cylinder block 1, which allows unidirectional flow from the front variable cavity 10 to the oil tank port 4. Combined with a tapered bushing 15 on the plug body 35 for opening the first one-way valve 7, when the braking force reaches its maximum, the first one-way valve 7 is opened, and the pressurized oil in the front variable cavity 10 flows back to the oil tank through the first one-way valve 7. The first one-way valve 7 is mounted on the cylinder block, reducing production and assembly difficulty and facilitating maintenance and replacement.

[0041] The present invention provides a large cavity 3 and a small cavity 2 in the cylinder body 1. The diameter of the large cavity 3 is larger than the diameter of the small cavity 2. When the first one-way valve 7 is opened, the piston can exert a multiplied pressure on the hydraulic oil in the small cavity 2, which can achieve a good power-assisted braking effect and is suitable for large machinery.

[0042] Furthermore, the piston 9 is provided with a first piston oil port 16, a first piston sealing ring 17, a second piston oil port 18, a second piston sealing ring 19, a third piston oil port 20, and a third piston sealing ring 21 in sequence along its outer edge away from the small cavity 2. Each piston sealing ring is installed on the outward protruding ring 22 of the piston 9 and is in close contact with the inner wall of the cylinder 1. Each piston oil port is used to connect the large cavity 3 and the inner cavity of the piston 9. The third piston sealing ring 21 and the tail end of the cylinder 1 form the rear variable cavity 11.

[0043] The piston 9 has an axially movable reversing valve core 13 inside its cavity. The end of the reversing valve core 13 away from the small cavity 2 passes through the tail end of the cylinder body 1 and is sealed to the cylinder body 1 by a fourth valve core sealing ring 23. The reversing valve core 13 has a first valve core sealing ring 24, a first valve core oil port 25, a second valve core sealing ring 26, a third valve core sealing ring 27, a second valve core oil port 28, and a third valve core oil port 29 arranged sequentially along the direction away from the small cavity 2. The third valve core oil port 29 is connected to the rear variable cavity 11.

[0044] Furthermore, a piston spring 30 is provided inside the front variable cavity 10 and outside the piston 9. One end of the piston spring 30 is sleeved on the plug body 35, and the other end is sleeved on the positioning ring 31 that extends in the direction of the large cavity 3 from the separation surface of the large cavity 3 and the small cavity 2. The tapered bushing 15 is displaced outside the piston spring 30.

[0045] The positioning ring 31 is provided with a positioning ring oil port 32 for connecting the large cavity 3 and the small cavity 2. When the piston 9 just begins to move forward, the first piston sealing ring 17 has not yet blocked the oil tank oil port 4 and the front variable cavity 10. The pressure in the front variable cavity 10 is very small, the second one-way valve 12 is not open, and the piston positioning ring oil port 32 is used to connect the front variable cavity 10 and the small cavity 2, so that the pressurized oil in the front variable cavity 10 can enter the small cavity 2, so that the small cavity 2 and the brake pad oil circuit are filled with hydraulic oil, and the brake pad is close to the brake disc.

[0046] A reversing spring 33 is provided between the end of the reversing valve core 13 near the small cavity 2 and the piston 9.

[0047] Furthermore, a neck 36 is provided between the plug head 34 and the plug body 35. The diameter of the neck 36 is smaller than the diameter of the plug head 34 and the diameter of the small cavity 2. A channel connecting the front variable cavity 10 and the small cavity 2 is provided on the neck 36.

[0048] As a preferred embodiment of the present invention, an exhaust port is provided on the cylinder body 1 at the position corresponding to the small cavity 2, and a vent plug 37 is installed in the exhaust port. Both the vent plug 37 and the exhaust port are stepped, and a sealing ring is provided on the outer side of the smaller diameter end of the vent plug 37.

[0049] Furthermore, the first one-way valve 7 includes a valve core whose head extends into the large cavity 3, a compression spring located at the tail of the valve core, and a sealing valve stem threaded onto the cylinder 1 for constraining the compression spring.

[0050] During operation, depending on the position of the reversing valve, there are two braking modes: unassisted braking mode and assisted braking mode. Assisted braking mode is a follow-up to unassisted braking mode.

[0051] The following describes in detail the working process of the braking device in its unassisted mode.

[0052] like Figure 1 As shown, the braking device is in its initial state, at which time the oil tank hole, large cavity 3, first piston 9 oil hole, valve core cavity, first valve core oil hole, second piston 9 oil hole, second valve core oil hole, third valve core oil hole and variable cavity are all connected to each other or indirectly.

[0053] At this time, the reversing valve core 13 and piston 9 are in a balanced / stationary state, and the small chamber 2 and the brake caliper oil chamber are filled with hydraulic oil, such as Figure 5 As shown.

[0054] like Figure 3As shown, when the brake pedal is pressed, the pedal transmits force to the reversing valve core 13, which moves to the left end of the piston 9 (after which the reversing valve core 13 and the piston 9 are relatively stationary). The reversing spring 33 is compressed, the first valve core sealing ring 24 blocks the first piston oil port 16, the second valve core sealing ring 26 blocks the second piston oil port 18, and the third valve core sealing ring 27 passes over the third piston oil port 20, connecting the third piston oil port 20, the oil pump oil port 5, the second valve core oil port 28, the third valve core oil port 29, and the variable volume chamber. The pressure oil from the oil pump is transmitted to the variable volume chamber at the right end of the cylinder 1, forming a leftward pressure, which, together with the foot pedal force, pushes the piston 9 to move to the left. At this time, the oil in the small chamber 2 shows a tendency to move to the left (but has not yet moved).

[0055] Figure 4 and Figure 5 The diagram shows piston 9 continuously moving to the left until the first piston seal ring 17 passes the oil tank port 4, cutting off the connection between the oil tank port 4 and the large chamber 3. At this point, the space where piston spring 30 is located forms a sealed cavity. As piston 9 continues to move to the left, the oil in this cavity enters the small chamber 2 through the second one-way valve 12. When the friction pads on the brake caliper are in close contact with the brake disc on the wheel drum, the piston 9 and the reversing valve core 13 move to the left, which is actually a hydraulic transmission.

[0056] At this point, the theoretical model of hydraulic transmission is as follows: Figure 6 As shown, this is the no-help mode. The specific principle is as follows:

[0057] according to Figure 6 The theoretical model yields the equilibrium equations:

[0058] P1A1+P3A3=P2A2 (1)

[0059] P2 here should also include the pedaling force. The pedaling force F is relatively small, actually not exceeding 20N, so it is ignored in the above formula.

[0060] D = 2d;

[0061] D - The diameter of piston A2, which is the diameter of the large chamber 3;

[0062] d - The diameter of piston A1, which is the diameter of small cavity 2;

[0063]

[0064] Substituting the calculated areas of A1, A2, and A3 into formula (1), we get:

[0065]

[0066] P1 + 3P3 = 4P2 (2)

[0067] from Figure 6 It can be seen that at this time, we are in the hydraulic transmission stage, P1≈P3 (from... Figure 9 It can be seen that P1 and P3 are connected through a check valve, and the opening pressure of the check valve is very small at 0.035MPa.

[0068] That is, equation (2) can be transformed into 4P1=4P2, then P1=P2. This state means that when the oil tank opening is sealed, there is oil pressure in chamber A3 (small chamber 2), and this pressure is equal to the pressure of the oil pump.

[0069] The working process of the assistance mode is as follows.

[0070] Figure 7 This indicates the state when piston 9 continues to move to the left, and tapered sleeve 15 touches the head of first check valve 7, but first check valve 7 is not opened. At this time, it is still in an unassisted state, which is the theoretical mode and Figure 6 same.

[0071] like Figure 8 As shown, when the tapered bushing 15 touches the first check valve 7 and opens it, the oil tank port 4 is connected to the large chamber 3 through the branch 6. At this time, P3 = 0, and the pressure of the brake left chamber oil P1 > P3, so the second check valve 12 is closed.

[0072] At this point, the theoretical model is as follows: Figure 9 When piston 9 continues to move to the left, the pressure of the liquid in small chamber 2 is compressed and expanded, following the following rule.

[0073] Liquid volume compressibility κ:

[0074]

[0075] κ—Liquid volume compressibility (m 2 / N);

[0076] K — Bulk modulus of elasticity of liquid (N / m) 2 );

[0077] V — Initial volume of the closed volume (m³) 3 );

[0078] ΔV—The amount of compression of the closed volume after being compressed (m) 3 );

[0079] ΔP—Gate pressure of hydraulic oil in the sealed cavity after pressurization (N / m) 2 );

[0080] Transforming equation (3) yields

[0081] Because Δp = P 液 -p. (5)

[0082] p — Initial hydraulic pressure of the sealed cavity (N / m) 2 Its initial pressure is atmospheric pressure, that is, the gauge pressure is 0 N / m. 2 .

[0083] P 液 —The pressure after the sealed cavity expands refers to Figure 9 P1 (N / m) 2 )

[0084] Therefore, Δp = P 液 -p. =P 液 -0 = P 液 (6) Substituting equation (6) into equation (4) yields

[0085] The value of K is generally in the range of (0.7-1.4)×10 3 MPa (see "Hydraulic Transmission", edited by Wang Jiwei of Southeast University, 2nd edition, Machinery Industry Press, January 2013, p. 11).

[0086] Let K = 1.0 × 10 3 MPa, the volume of the oil is compressed.

[0087] but

[0088] This means that when the volume of hydraulic oil is compressed by 1 / 100, the oil pressure in the sealed volume can rise to 10 MPa.

[0089] D = 2d

[0090] Depend on Figure 9 It can be seen that the force on the brake piston 9 should satisfy the equilibrium relationship P1A1=P2A2(8).

[0091]

[0092] P1 = 4P2 (9)

[0093] That is, the hydraulic pressure P1 on the brake disc is 4 times the oil pump supply pressure P2, and there is a force-increasing relationship between them.

[0094] Figure 10 Indicates in Figure 8 Based on this, the reversing valve core 13 and piston 9 move to the left under the combined action of the variable cavity and the foot pedal force, and the piston spring 30 is compressed to its limit position.

[0095] Figure 11This indicates that after the tractor is brought to a stop, the foot releases the pedal, and the reversing valve core 13 moves to the right under the action of the reversing spring 33, returning to the initial relative position of the reversing valve core 13 and the piston 9. At this time, the space where the piston spring 30 is located, the first piston oil port 16, the valve core cavity, the first valve core oil port 25, the third valve core oil port 29, and the variable volume cavity are connected. The third valve core sealing ring 27 moves backward past the third piston oil port 20, disconnecting the connection between the third piston oil port 20 and the second valve core oil port 28, and replenishing oil to the space where the piston spring 30 is located. The variable volume cavity quickly releases pressure, and the piston spring 30 automatically pushes the piston 9 to the right to reset.

[0096] The piston spring 30 automatically pushes the piston 9 and the reversing valve core 13 to move to the right and return to the initial state, completing the entire working cycle of the braking function. Figure 1 As shown.

[0097] The power-assisted braking device in this invention, through the arrangement of piston 9, reversing valve core 13, and each oil port (i.e., each sealing ring), has an initial non-powered braking mode and a later power-assisted braking mode, and the power-assisted braking mode is a subsequent mode of the non-powered braking mode, which is suitable for braking large tractors.

[0098] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A power brake device for a brake, characterized in that, a cylinder (1) is provided with a small cavity (2) and a large cavity (3) in communication with each other in the axial direction, the diameter of the large cavity (3) is larger than that of the small cavity (2), the cylinder (1) is provided with an oil tank oil port (4) connected with an oil tank and an oil pump oil port (5) connected with an oil pump at the position corresponding to the large cavity (3), the oil tank oil port (4) is further provided with a branch (6) connected with the large cavity (3) near the side of the small cavity (2), and a first one-way valve (7) for one-way conduction to the oil tank oil port (4) is installed in the branch (6), and the cylinder (1) is provided with a brake oil port (8) connected with a brake actuating component at the side away from the small cavity (2); a piston (9) is arranged in the cylinder (1), the plug head (34) of the piston (9) is located in the small cavity (2), and a plug head (34) sealing ring is arranged on the outer wall of the plug head (34), the plug body (35) of the piston (9) is formed with a front variable cavity (10) and a rear variable cavity (11) between the plug body (35) and the cylinder (1) at the front and rear ends respectively, a hole is arranged in the plug head (34) to communicate the small cavity (2) and the front variable cavity (10), and a second one-way valve (12) for one-way conduction to the small cavity (2) is arranged in the hole; a reversing valve core (13) is arranged in the piston (9), the reversing valve core (13) is provided with a valve core inner cavity (14) in communication with the rear variable cavity (11) at the center, an oil port and a sealing ring are arranged on the reversing valve core (13) and the piston (9) respectively, the reversing valve core (13) can move axially to control the communication between the rear variable cavity (11) and the oil pump oil port (5), so that the oil pump assists the piston (9) to move to provide brake power, or the rear variable cavity (11) is in communication with the oil tank oil port (4), so that the pressure oil in the rear variable cavity (11) returns to the oil tank to release pressure; the piston (9) can move to the front variable cavity (10) to block the communication between the oil tank oil port (4) and the front variable cavity (10), and press the pressure oil in the front variable cavity (10) into the small cavity (2) to make the brake pad close to the brake disc; a conical shaft sleeve (15) for opening the first one-way valve (7) is arranged on the outer part of one end of the plug body (35) located in the front variable cavity (10), so that when the brake force reaches the maximum, the pressure oil in the front variable cavity (10) returns to the oil tank through the first one-way valve (7).

2. The power brake device for a brake according to claim 1, characterized in that, The outer edge of the piston (9) is sequentially provided with a first piston oil port (16), a first piston sealing ring (17), a second piston oil port (18), a second piston sealing ring (19), a third piston oil port (20) and a third piston sealing ring (21) away from the small cavity (2), each piston sealing ring is installed on the outward convex ring (22) of the piston (9) and is in close contact with the inner wall of the cylinder (1), and each piston oil port is used for connecting the large cavity (3) and the inner cavity of the piston (9), and the third piston sealing ring (21) and the tail end of the cylinder (1) form the rear variable cavity (11); The inner cavity of the piston (9) is provided with an axial movable reversing valve core (13), one end of the reversing valve core (13) away from the small cavity (2) penetrates the tail end of the cylinder (1) and is sealed with the cylinder (1) through a fourth valve core sealing ring (23), and the reversing valve core (13) is sequentially provided with a first valve core sealing ring (24), a first valve core oil port (25), a second valve core sealing ring (26), a third valve core sealing ring (27), a second valve core oil port (28) and a third valve core oil port (29) away from the small cavity (2), and the third valve core oil port (29) communicates with the rear variable cavity (11).

3. The power brake device for a brake according to claim 1, wherein The front variable cavity (10) is provided with a piston spring (30) outside the piston (9), one end of the piston spring (30) is sleeved on the plug body (35), the other end is sleeved on a positioning ring (31) extending to the large cavity (3) from the separation surface of the large cavity (3) and the small cavity (2), and the conical shaft sleeve (15) is displaced outside the piston spring (30); The positioning ring (31) is provided with a positioning ring oil port (32) for communicating the large cavity (3) and the small cavity (2); The reversing spring (33) is arranged between the end of the reversing valve core (13) close to the small cavity (2) and the piston (9).

4. The power brake device for a brake according to claim 1, wherein The plug head (34) and the plug body (35) are further provided with a plug neck (36), the diameter of the plug neck (36) is smaller than the diameter of the plug head (34) and the diameter of the small cavity (2), and the plug neck (36) is provided with a channel connecting the front variable cavity (10) and the small cavity (2).

5. The power brake device for a brake according to claim 1, wherein The cylinder (1) is provided with an exhaust port corresponding to the position of the small cavity (2), and the exhaust port is provided with a deflation plug (37), the exhaust port and the deflation plug (37) are both in a stepped shape, and the deflation plug (37) is provided with a sealing ring outside the smaller end.

6. The power brake device for a brake according to claim 1, wherein The first one-way valve (7) comprises a valve core with a head extending into the large cavity (3), a compression spring at the tail of the valve core, and a sealing valve rod threadedly connected to the cylinder body (1) for restraining the compression spring.

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