An electronic brake booster with mechanical backup function

Abstract

The present invention relates to the technical field of electronic brake boosters, and in particular to an electronic brake booster with a mechanical backup function, which includes a PFS housing, a support seat, a guide base, an input push rod, a main guide rod, a central bevel gear, a main shaft, a buffer seat and an output push rod, wherein the main guide rod is installed in the guide base and the front portion thereof extends into the central hole of the main shaft, the rear portion of the main guide rod is fixed with a support seat, a secondary spring is arranged between the support seat and the guide base, a tertiary spring is fixed on the support seat, the front end of the input push rod is connected to the main guide rod, a primary spring is clamped on the input push rod, the central bevel gear is threadedly matched with the main shaft, the buffer seat includes an insertion portion and an ejection portion, the insertion portion is provided with a step and the front portion of the step is inserted into the central hole of the main shaft. The device provided by the present invention can provide mechanical backup braking when the electric control fails and there is no power assistance, thereby improving the safety of the braking system.

Description

Technical Field

[0001] The invention relates to the technical field of electronic brake boosters, and in particular to an electronic brake booster with a mechanical backup function. Background Art

[0002] The electronic brake booster needs to transfer the power of the motor to the central bevel gear, and then realize the linear motion of the main shaft through the rotation of the central bevel gear, and transfer the power to the master cylinder to assist the master cylinder to realize the braking of the vehicle braking system. However, because the main shaft of the electronic brake booster and the central bevel gear convert the rotational motion into linear motion, the guide rod in the prior art is pushed by the input push rod to slide along the guide seat, but its front end does not contact the main shaft. The electronic brake booster with this structure cannot provide mechanical backup braking when the electronic control fails and there is no power assistance, making the safety of the braking system relatively poor. Summary of the invention

[0003] The present invention protects an electronic brake booster with a mechanical backup function, which can provide mechanical backup braking when the electronic control fails and there is no assistance, thereby improving the safety of the braking system and preventing the main shaft from rotating to affect the braking assistance effect of the electronic brake booster. At the same time, the operating noise is small, the center bevel gear has a long service life and can withstand large axial impact loads.

[0004] The present invention is achieved through the following technical solutions:

[0005] An electronic brake booster with a mechanical backup function comprises a PFS housing, a support seat, a guide base, an input push rod, a main guide rod, a center bevel gear, a main shaft, a buffer seat and an output push rod, wherein the guide base is located at the front part of the PFS housing, the main guide rod is slidably installed in the guide base, the front part of the main guide rod extends into the center hole of the main shaft, the rear part of the main guide rod is fixedly installed with a support seat, a secondary spring is provided between the support seat and the guide base, a tertiary spring is fixedly installed on the support seat, the front end of the input push rod passes through the PFS housing and is connected to the main guide rod, a primary spring is clamped on the input push rod, the center bevel gear is installed on the mounting seat and cooperates with the main shaft thread, the buffer seat comprises an insertion portion and a push-out portion, the insertion portion is provided with a step and the front part of the step is inserted into the center hole of the main shaft, and the push-out portion is connected to the output push rod.

[0006] Furthermore, a first buffer pad is provided between the main guide rod and the insertion portion of the buffer seat, and a shock-absorbing pad is fixedly mounted on the push-out portion of the buffer seat.

[0007] Furthermore, a bushing is fixedly mounted on the main guide rod, and the bushing is slidably matched with the inner hole of the guide base. Furthermore, a main guide rod inner hole is provided at the rear of the main guide rod, a decoupling stroke is provided in the main guide rod inner hole, and a second buffer pad is installed between the main guide rod inner hole and the input push rod.

[0008] Furthermore, the mounting seat is fixedly connected to the guide base, a fixed shell and an upper cover are fixedly installed on the mounting seat, the fixed shell is sleeved on the outside of the PFS shell, the upper cover is fixedly connected to the master cylinder, and the output push rod is connected to the master cylinder piston.

[0009] Furthermore, the upper cover, the main cylinder and the mounting seat are respectively provided with corresponding auxiliary guide rod mounting holes, and an auxiliary guide rod is arranged in the auxiliary guide rod mounting holes of the upper cover, the main cylinder and the mounting seat, and the bottom of the auxiliary guide rod is arranged on a limiting flange, and the top is provided with an external thread and is locked and fixed with the main cylinder by a locking nut. The auxiliary guide rod and the auxiliary guide rod mounting holes of the upper cover and the main cylinder are threaded or interference fit, and the bottom of the auxiliary guide rod passes through the auxiliary guide rod mounting hole of the mounting seat with a clearance fit. An anti-rotation support plate is fixedly installed on the main shaft, and both ends of the anti-rotation support plate are slidably connected with the two auxiliary guide rods through sliding bearings, and more than two anti-rotation ribs are fixedly provided on the inner wall of the upper cover, the front diameter of the auxiliary guide rod is smaller than the rear, and the movable clearance between the anti-rotation rib and the anti-rotation support plate is smaller than the clearance between the inner hole of the sliding bearing and the front outer diameter of the auxiliary guide rod and is larger than the clearance between the inner hole of the sliding bearing and the rear outer diameter of the auxiliary guide rod.

[0010] Further, the central bevel gear comprises a central bevel gear inner ring and a central bevel gear outer ring fixed as one, the central bevel gear inner ring is provided with an inner ring center hole with an internal thread, the outer surface of the central bevel gear inner ring is provided with a plurality of vertical grooves along the axial direction, the central bevel gear outer ring is provided with a plurality of gear teeth and an outer ring center hole matched with the outer surface of the central bevel gear inner ring, the outer ring center hole is provided with a plurality of spur teeth matched with the plurality of vertical grooves of the central bevel gear inner ring, and an axial limit is provided between the outer surface of the central bevel gear inner ring and the central hole of the central bevel gear outer ring. Further, the outer surface of the central bevel gear inner ring is a truncated cone structure with an inclination.

[0011] Optimally, the axial limit is a bottom axial limit or a top axial limit, or both the bottom axial limit and the top axial limit are set between the outer surface of the inner ring of the central helical gear and the center hole of the outer ring of the central helical gear. Optimally, the inner ring of the central helical gear is a wear-resistant inner ring of the central helical gear, and the outer ring of the central helical gear is a high-strength outer ring of the central helical gear.

[0012] Advantageous Effects of the Invention

[0013] The electronic brake booster with mechanical backup function protected by the present invention has the following advantages:

[0014] 1. When the electronic control fails and there is no power assistance, it can provide mechanical backup braking, which improves the safety of the braking system;

[0015] 2. It can support the energy recovery of the braking system and improve the performance of the braking system;

[0016] 3. It can prevent the main shaft from rotating and affecting the braking effect of the electronic brake booster;

[0017] 4. The center helical gear is easy to manufacture and has a long service life;

[0018] 5. The noise is relatively small when the center helical gear and the main shaft are running together;

[0019] 6. The center helical gear can withstand large axial impact loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention;

[0021] Figure 2 It is a schematic diagram of the connection structure between the output push rod and the master cylinder piston;

[0022] Figure 3 This is a schematic diagram of the anti-rotation structure;

[0023] Figure 4 It is a schematic diagram of the assembly structure of one specific implementation method of the central helical gear;

[0024] Figure 5 This is a schematic diagram of the structure of the outer ring of the center helical gear in one specific implementation manner;

[0025] Figure 6 It is a schematic diagram of the inner ring structure of the center helical gear according to one specific implementation method.

[0026] Figure 7 It is a schematic diagram of the assembly structure of the second specific implementation method of the central helical gear;

[0027] Figure 8 It is a schematic diagram of the third assembly structure of the specific implementation method of the central helical gear;

[0028] In the figure, 1. input push rod, 2. PFS housing, 3. support seat, 4. secondary spring, 5. auxiliary guide rod, 6. upper cover, 7. main cylinder, 8. output push rod, 9. shock absorber, 10. anti-rotation support plate, 11. buffer seat, 12. mounting seat, 13. first buffer pad, 14. main shaft, 15. guide base, 16. main guide rod, 17. third spring, 18. second buffer pad, 19. first spring, 20. center bevel gear, 2 1. Fixed housing, 22. Decoupling stroke, 23. Bushing, 24. Center helical gear outer ring, 25. Helical teeth, 26. Center helical gear inner ring, 27. Bottom axial limit, 28. Cone-shaped structure, 29. Top limit flange, 30. Outer ring center hole, 31. Straight teeth, 32. Vertical grooves, 33. Internal threads, 34. Inner ring center hole, 35. Locking nut, 36. Push rod sleeve, 37. Master cylinder piston, 38. Sliding bearing. DETAILED DESCRIPTION

[0029] An electronic brake booster with a mechanical backup function comprises a PFS housing 2, a support seat 3, a guide base 15, an input push rod 1, a main guide rod 16, a center bevel gear 20, a main shaft 14, a buffer seat 11 and an output push rod 8, wherein the guide base is located at the front of the PFS housing, the main guide rod is slidably installed in the guide base, the front part of the main guide rod extends into the center hole of the main shaft, the rear part of the main guide rod is fixedly installed with a support seat, a secondary spring 4 is provided between the support seat and the guide base, a tertiary spring 17 is fixedly installed on the support seat, the front end of the input push rod passes through the PFS housing and is connected to the main guide rod, a primary spring 19 is clamped on the input push rod, the center bevel gear is installed on the mounting seat 12 through a bearing and cooperates with the main shaft thread, the buffer seat comprises an insertion portion and a push-out portion, the insertion portion is provided with a step and the front part of the step is inserted into the center hole of the main shaft, and the push-out portion is connected to the output push rod.

[0030] The electronic brake booster protected by this application has the following working process:

[0031] The pedal force acts on the input push rod, first pushing the first-stage spring to compress, and the front end of the input push rod contacts the main guide rod, compressing the second-stage spring and the third-stage spring in turn, thereby pushing the main guide rod forward. The displacement sensor (not shown) senses the movement of the input push rod and transmits a signal to the control system (not shown). The control system controls the motor (not shown) to drive the central bevel gear to rotate. A reduction mechanism can be set in the middle. Since the central bevel gear is installed on the main shaft and cooperates with the main shaft thread, the rotation of the central bevel gear will cause the main shaft to move forward linearly, thereby pushing the buffer seat forward, and then the buffer seat pushes the output push rod forward to push the master cylinder piston forward, providing braking assistance for the brake system, and the push rod sleeve 36 can be installed between the output push rod and the inner hole of the master cylinder piston to ensure that the output push rod is coaxial with the master cylinder piston 37, so that the output push rod and the master cylinder piston can run stably and linearly.

[0032] Note: The motor, control system, deceleration mechanism and displacement sensor are all prior art, so they are not shown in the attached drawings. When the control system fails and there is no power assistance, that is, the motor cannot drive the central bevel gear to rotate, the main shaft cannot achieve reciprocating linear motion. Since the front part of the main guide rod extends into the center hole of the main shaft, the buffer seat includes an insertion part and a push-out part. The insertion part is provided with a step and the front part of the step is inserted into the center hole of the main shaft. A first buffer pad is provided between the main guide rod and the insertion part of the buffer seat. The push-out part is connected to the output push rod. The main guide rod can still move forward to push the buffer seat forward, and then push the output push rod forward to push the piston of the master cylinder 7 forward, providing mechanical backup braking for the braking system and improving the safety of the vehicle braking system.

[0033] Since the front part of the main guide rod extends into the center hole of the main shaft, the buffer seat includes an insertion part and a push-out part. The insertion part is provided with a step and the front part of the step is inserted into the center hole of the main shaft, and the push-out part is connected to the output push rod. This arrangement can ensure that when the control system is working normally, the linear motion of the main shaft pushes the buffer seat forward, and when the control system fails, the main guide rod pushes the buffer seat forward, thereby realizing the mechanical backup braking of the braking system and being able to keep the main guide rod and the main shaft running coaxially and linearly at all times, so that the operation is smoother.

[0034] Only the clearance fit between the buffer seat and the main shaft can ensure the relative sliding between the buffer seat and the main shaft when the control system fails. When the control system is working normally, the motor always gives the main shaft a forward force through the center bevel gear to push the buffer seat forward, so that the main guide rod and the buffer seat do not contact, and the main shaft and the buffer seat remain fixed and will not separate. During the electronic power-assisted return process, the motor still gives the main shaft a forward force through the center bevel gear, so that the main shaft and the buffer seat remain fixed and will not separate, and the reverse pressure at the main cylinder end will also prevent the buffer seat from separating from the main shaft, and the main guide rod retracts under the action of the spring restoring force. Furthermore, a first buffer pad 13 is provided between the main guide rod and the insertion portion of the buffer seat to reduce the impact force between the main guide rod and the buffer seat, and a shock-absorbing pad 9 is fixedly installed on the push-out portion of the buffer seat to reduce the impact force between the output push rod and the buffer seat.

[0035] Furthermore, a bushing 23 is fixedly mounted on the main guide rod, and the bushing is slidably matched with the inner hole of the guide base. The bushing and the inner hole of the guide base are matched, and the two can slide relative to each other. Through this guiding action, the movement direction of the main guide rod can be made coaxial with the main shaft, reducing internal friction and thus optimizing the pedal feel.

[0036] Furthermore, a main guide rod inner hole is provided at the rear of the main guide rod, and a decoupling stroke 22 is provided in the main guide rod inner hole, and the distance of the decoupling stroke is preferably about 10 mm. The decoupling stroke is set so that the input push rod and the output push rod are not connected within the decoupling stroke range at the initial stage of the stroke, so that the pedal force will not be transmitted to the master cylinder and the braking pressure will not be established. When the deceleration in the return stage is relatively small, the input end of the electronic brake booster is within the decoupling stroke. At this time, the braking is completed by motor energy recovery, and the output end of the electronic brake booster does not intervene, which can support a certain amount of energy recovery. On the one hand, it can maximize the cruising range, and on the other hand, it can also extend the life of the brake pads. A second buffer pad 18 is installed between the main guide rod inner hole and the input push rod to reduce the impact force between the input push rod and the main guide rod.

[0037] Furthermore, the mounting seat is fixedly connected to the guide base, and a fixed housing 21 and an upper cover 6 are fixedly installed on the mounting seat. The fixed housing is sleeved on the outside of the PFS housing, and the PFS housing can move with the movement of the input push rod. In this way, the main part of the displacement sensor can be fixedly installed on the fixed housing, and the sensing sheet can be fixedly installed on the PFS housing to realize the displacement sensor sensing the movement of the input push rod. The upper cover is fixedly connected to the master cylinder 7, and the output push rod is connected to the master cylinder piston. In this way, the internal structure of the electronic brake booster can be protected, and dustproof and waterproof effects can be achieved.

[0038] Optimized, the upper cover, the master cylinder and the mounting seat are respectively provided with corresponding auxiliary guide rod mounting holes, the auxiliary guide rod mounting holes of the upper cover, the master cylinder and the mounting seat are provided with auxiliary guide rods 5, and the bottom of the auxiliary guide rod is provided at the limiting flange, the top is provided with external threads and is locked and fixed with the master cylinder by a locking nut 35, the auxiliary guide rod and the auxiliary guide rod mounting holes of the upper cover and the master cylinder are threaded or interference fit, the bottom of the auxiliary guide rod is passed through the auxiliary guide rod mounting hole of the mounting seat with a clearance fit and is limited by the limiting flange. In this way, after the upper cover and the master cylinder are installed, the auxiliary guide rod can be passed through the auxiliary guide rod mounting hole of the mounting seat, the sliding bearing, the upper cover and the auxiliary guide rod mounting hole of the master cylinder in turn, the bottom is limited by the limiting flange, and the top is locked with the master cylinder by the locking nut, and the assembly of the auxiliary guide rod is very convenient and quick.

[0039] An anti-rotation support plate 10 is fixedly mounted on the main shaft, and both ends of the anti-rotation support plate are slidably mounted on two auxiliary guide rods, and anti-rotation ribs are fixedly mounted on the inner wall of the upper cover. Specifically, the anti-rotation support plate and the auxiliary guide rod can be connected via a sliding bearing 38 mounted on the anti-rotation support plate. Since the anti-rotation support plate is fixedly mounted on the top of the main shaft, the anti-rotation support plate will reciprocate linearly with the main shaft, and since the anti-rotation support plate is slidably connected to the auxiliary guide rod, the rotation of the anti-rotation support plate is limited, and then the rotation of the main shaft is also limited, thereby achieving stable linear operation of the main shaft. Anti-rotation ribs are fixedly mounted on the inner wall of the upper cover, and there are at least two anti-rotation ribs, which can limit the rotation range of the anti-rotation tray along the center of the main shaft, so that the auxiliary guide rod can smoothly pass through the sliding bearing on the anti-rotation tray.

[0040] And it can be further limited that the front diameter of the secondary guide rod is smaller than the rear end diameter, and the movable clearance between the anti-rotation rib and the anti-rotation support plate is smaller than the clearance between the inner hole of the sliding bearing and the front outer diameter of the secondary guide rod and larger than the clearance between the inner hole of the sliding bearing and the rear outer diameter of the secondary guide rod. In this way, when the secondary guide rod is assembled, since the movable clearance between the anti-rotation rib and the anti-rotation support plate is smaller than the clearance between the inner hole of the sliding bearing and the front outer diameter of the secondary guide rod, it can be ensured that even if the anti-rotation support plate has a certain rotation, the secondary guide rod can still pass through the sliding bearing smoothly, and the movable clearance between the anti-rotation rib and the anti-rotation support plate is larger than the clearance between the inner hole of the sliding bearing and the rear outer diameter of the secondary guide rod, thereby ensuring that during operation, the anti-rotation support plate will not touch the anti-rotation rib when the main shaft moves up and down, thereby affecting the operation of the main shaft.

[0041] Furthermore, the center bevel gear includes a center bevel gear inner ring 26 and a center bevel gear outer ring 24 fixed as one, the center bevel gear inner ring is provided with an inner ring center hole 34 with an internal thread 33, the outer surface of the center bevel gear inner ring is provided with a plurality of vertical grooves 32 along the axial direction, the center bevel gear outer ring is provided with a plurality of gear teeth 25 and an outer ring center hole 30 matched with the outer surface of the center bevel gear inner ring, the outer ring center hole is provided with a plurality of spur teeth 31 matched with the plurality of vertical grooves of the center bevel gear inner ring, and an axial limit is provided between the outer surface of the center bevel gear inner ring and the center hole of the center bevel gear outer ring.

[0042] The center helical gear is divided into two parts, including a center helical gear inner ring and a center helical gear outer ring. During production, the center helical gear outer ring can be firstly formed by injection molding or metal processing, and then formed into an integrated center helical gear assembly with the center helical gear inner ring by secondary injection molding, two-color injection molding or metal coating, which is convenient to process and produce.

[0043] In addition, an axial limit is provided between the outer surface of the inner ring of the center helical gear and the center hole of the outer ring of the center helical gear. When the inner ring of the center helical gear cooperates with the main shaft thread and bears a large axial load, the outer ring of the center helical gear needs to cooperate with other gears and the axial position is relatively fixed. The inner ring of the center helical gear will not move axially, which can not only reduce the operating noise, but also improve the ability of the center helical gear to withstand axial loads and ensure that the inner ring of the center helical gear and the outer ring of the center helical gear will not separate during operation.

[0044] The outer surface of the inner ring of the center bevel gear is provided with a plurality of vertical grooves, and the center hole of the outer ring is provided with a plurality of straight teeth that cooperate with the plurality of vertical grooves of the inner ring of the center bevel gear. This not only facilitates the secondary processing and forming of the two components into one body, but also prevents relative rotation between the two components, thereby transmitting the rotation of the outer ring of the center bevel gear to the inner ring of the center bevel gear, so that the two rotate synchronously.

[0045] Optimally, the outer surface of the inner ring of the central helical gear is a truncated cone-shaped structure with an inclination 28. Since the outer surface of the inner ring of the central helical gear is a truncated cone-shaped structure with an inclination, and the outer ring of the central helical gear matches the outer surface of the inner ring of the central helical gear, a draft angle is formed between the two components, which is convenient for secondary injection molding and can increase the axial load-bearing capacity.

[0046] Further, the axial limit is a bottom axial limit 27 or a top axial limit 29 provided between the outer surface of the inner ring of the central helical gear and the central hole of the outer ring of the central helical gear, or the bottom axial limit and the top axial limit are provided at the same time. Figure 2 , 5 As shown in Figure 6, when the outer surface of the inner ring of the center bevel gear is a vertical structure, the bottom axial limit and the top axial limit can be set at the same time; if the outer surface of the inner ring of the center bevel gear is a truncated cone structure with an inclination, only one bottom axial limit or top axial limit can be set, so as to improve the carrying capacity of the center bevel gear; when the inner ring of the center bevel gear cooperates with the main shaft thread, the outer ring of the center bevel gear rotates, and the main shaft reciprocates up and down, the inner ring of the center bevel gear will not move axially, thereby reducing the noise during operation and extending the service life of the equipment. The specific bottom axial limit or top axial limit can be limited in the form of steps, or in other ways.

[0047] Furthermore, the inner ring of the central helical gear is a wear-resistant inner ring of the central helical gear, and specifically can be made of POM wear-resistant material or other wear-resistant materials, so that the inner ring of the central helical gear and the main shaft have good sliding properties.

[0048] Furthermore, the outer ring of the center helical gear is a high-strength center helical gear outer ring, which can be made of nylon material or other high-strength materials, such as fiber-reinforced plastic or other high-strength metal materials.

[0049] To sum up, the electronic brake booster with mechanical backup function protected by the present invention can provide mechanical backup braking when the electronic control fails and there is no assistance, thereby improving the safety of the braking system and preventing the main shaft from rotating and affecting the braking assistance effect of the electronic brake booster. At the same time, the operating noise is small, the center bevel gear has a long life and can withstand large axial impact loads.

[0050] For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electronic brake booster with mechanical backup function, characterized in that: It includes a PFS shell, a support seat, a guide base, an input push rod, a main guide rod, a center bevel gear, a main shaft, a buffer seat and an output push rod. The guide base is located at the front part of the PFS shell, the main guide rod is slidably installed in the guide base, the front part of the main guide rod extends into the center hole of the main shaft, and the rear part of the main guide rod is fixedly installed with a support seat, a secondary spring is provided between the support seat and the guide base, and a tertiary spring is fixedly installed on the support seat. The front end of the input push rod passes through the PFS shell and is connected with the main guide rod, and a primary spring is clamped on the input push rod. The center bevel gear is installed on the mounting seat and cooperates with the main shaft thread. The buffer seat includes an insertion part and a push-out part. The insertion part is provided with a step and the front part of the step is inserted into the center hole of the main shaft. The push-out part is connected with the output push rod, the rear part of the main guide rod is provided with a main guide rod inner hole, the inner hole of the main guide rod is provided with a decoupling stroke, and a second buffer pad is installed between the inner hole of the main guide rod and the input push rod.

2. The electronic brake booster with mechanical backup function according to claim 1, characterized in that: A first buffer pad is arranged between the main guide rod and the inserting portion of the buffer seat, and a shock-absorbing pad is fixedly installed on the pushing portion of the buffer seat.

3. The electronic brake booster with mechanical backup function according to claim 1, characterized in that: A bushing is fixedly sleeved on the main guide rod, and the bushing is slidably matched with the inner hole of the guide base.

4. The electronic brake booster with mechanical backup function according to claim 1, characterized in that: The mounting seat is fixedly connected to the guide base, and a fixed shell and an upper cover are fixedly installed on the mounting seat. The fixed shell is sleeved on the outside of the PFS shell, the upper cover is fixedly connected to the master cylinder, and the output push rod is connected to the master cylinder piston.

5. The electronic brake booster with mechanical backup function according to claim 4, characterized in that: The upper cover, main cylinder and mounting seat are respectively provided with corresponding secondary guide rod mounting holes, and the secondary guide rod mounting holes of the upper cover, main cylinder and mounting seat are provided with secondary guide rods, and the bottom of the secondary guide rod is provided with a limiting flange, the top is provided with an external thread and is locked and fixed with the main cylinder through a locking nut, the secondary guide rod and the upper cover and the secondary guide rod mounting holes of the main cylinder are threaded or interference fit, and the bottom of the secondary guide rod passes through the secondary guide rod mounting hole of the mounting seat with a clearance fit, an anti-rotation support plate is fixedly installed on the main shaft, and the two ends of the anti-rotation support plate are slidably connected with the two secondary guide rods through sliding bearings, and more than two anti-rotation ribs are fixedly provided on the inner wall of the upper cover, the front diameter of the secondary guide rod is smaller than the rear, and the active clearance between the anti-rotation rib and the anti-rotation support plate is smaller than the clearance between the inner hole of the sliding bearing and the front outer diameter of the secondary guide rod and is larger than the clearance between the inner hole of the sliding bearing and the rear outer diameter of the secondary guide rod.

6. The electronic brake booster with mechanical backup function according to claim 1, characterized in that: The center bevel gear includes a center bevel gear inner ring and a center bevel gear outer ring fixed as one, the center bevel gear inner ring is provided with an inner ring center hole with an internal thread, the outer surface of the center bevel gear inner ring is provided with a plurality of vertical grooves along the axial direction, the center bevel gear outer ring is provided with a plurality of gear teeth and an outer ring center hole matching with the outer surface of the center bevel gear inner ring, the outer ring center hole is provided with a plurality of spur teeth matching with the plurality of vertical grooves of the center bevel gear inner ring, and an axial limit is provided between the outer surface of the center bevel gear inner ring and the center hole of the center bevel gear outer ring.

7. The electronic brake booster with mechanical backup function according to claim 6, characterized in that: The outer surface of the inner ring of the central helical gear is a truncated cone structure with an inclination.

8. An electronic brake booster with mechanical backup function according to claim 6 or 7, characterized in that: The axial limit is a bottom axial limit or a top axial limit set between the outer surface of the inner ring of the center helical gear and the center hole of the outer ring of the center helical gear, or the bottom axial limit and the top axial limit are set at the same time.

9. An electronic brake booster with mechanical backup function according to claim 6 or 7, characterized in that: The inner ring of the central helical gear is a wear-resistant central helical gear inner ring, and the outer ring of the central helical gear is a high-strength central helical gear outer ring.

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