CN113119935A

CN113119935A - Electric brake booster with stop lock

Info

Publication number: CN113119935A
Application number: CN201911411567.7A
Authority: CN
Inventors: 章秋生
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-07-16
Also published as: JP2021109652A

Abstract

An electric brake booster for use in a vehicle comprising: a pedal force transmitting element for transmitting a pedal force from a brake pedal; a brake motor for performing a motor braking operation to generate a braking assist force; a power assist transmission element that axially pushes a piston of the master cylinder; and a stopper lock that switches between a stopper state and a stopper release state; the electric brake booster has a motor brake mode of operation and a pure pedal brake mode of operation; in the motor brake operating mode, the stop lock is placed in the stop release state, so that the pedal force transmission element and the power-assisted transmission element are kinematically decoupled, only the brake power generated by the brake motor being transmitted via the power-assisted transmission element to the piston of the brake master cylinder; in the pure pedal brake operating mode, the stop lock is placed in the stop state, so that the pedal force is transmitted via the pedal force transmission element, the stop lock and the power-assisted transmission element to the piston of the brake master cylinder.

Description

Electric brake booster with stop lock

Technical Field

The present application relates to an electric brake booster for use in a vehicle braking system.

Background

Some vehicles have added to their hydraulic braking systems an electric brake booster that utilizes an electric motor as a source of brake boost. In the case of electric brake boosters of the prior art, the brake booster and the pedal force are usually coupled via a transmission line, i.e. transmitted to the master cylinder piston via common force transmission elements. In such an electric brake booster, when a driver performs a braking operation, the driver presses a brake pedal to apply a pedal force, a motor of the electric brake booster generates a brake assist force, and the pedal force and the brake assist force are transmitted to a master cylinder piston in combination. For vehicles having an automatic braking function (e.g., an automatic driving or active braking module, etc.), the electric motor of the electric brake booster actively generates a braking assistance without driver intervention (i.e., no pedal force input) when the vehicle automatically applies braking. However, when the brake assist force is transmitted to the master cylinder piston, the pedal force transmitting member, and even the brake pedal, is pulled. This affects the transmission efficiency of the brake assist force and may give a driver a bad feeling of putting his foot on the brake pedal.

Disclosure of Invention

The present application is directed to providing an improved electric brake booster having a motor braking operation mode in which vehicle braking is achieved using only a braking assist of a brake motor, and a pure pedal braking operation mode in which vehicle braking can be rapidly achieved through a brake pedal.

To this end, according to one aspect of the present application, there is provided an electric brake booster for use in a vehicle brake system, comprising: a pedal force transmitting element configured to transmit a pedal force from a brake pedal; a brake motor configured to perform a motor braking operation to generate a braking assist force; a power assist transmission element configured to axially push a piston of the master cylinder; and a stopper lock provided on the power transmission element and configured to switch between a stopper state and a stopper release state; wherein the electric brake booster has a motor braking mode of operation and a pure pedal braking mode of operation; in the motor brake mode of operation, the stop lock is placed in a stop-released state, such that the pedal-force transmission element and the power-assist transmission element are kinematically decoupled, only the brake power generated by the brake motor being transmitted via the power-assist transmission element to the piston of the brake master cylinder; in the pure pedal brake operating mode, the stop lock is placed in the stop state, so that the pedal force is transmitted via the pedal force transmission element, the stop lock and the power-assisted transmission element to the piston of the brake master cylinder.

According to the application, when the motor braking operation is performed, the stop lock is released, so that the pedal force transmission line and the brake boosting transmission line are decoupled, and therefore the pedal force transmission element and the brake boosting transmission element cannot interfere with each other. When the motor braking operation is performed, the input force of the electric brake booster is derived only from the brake motor without combining the pedal force. On the other hand, when a pure pedal braking operation is performed, the stopper lock reduces the idle stroke of the pedal force transmission element, thereby achieving rapid vehicle braking.

Drawings

FIG. 1 is a schematic cross-sectional view (through a booster center axis) of an electric brake booster according to one possible embodiment of the present application;

FIG. 2 is a schematic cross-sectional view of the electric brake booster in another direction (through the booster center axis in a direction perpendicular to FIG. 1);

FIG. 3 is a schematic view for explaining a pedal force transmission line in the electric brake booster;

FIG. 4 is a schematic diagram for explaining a brake assist transmission line in the electric brake booster;

FIGS. 5 and 6 are schematic views of a drive nut and a plunger, respectively, in an electric brake booster;

FIG. 7 is a schematic illustration of a pedal spring in an electric brake booster;

FIGS. 8 and 9 are schematic views of the constituent elements of one possible embodiment of a pedal spring limit structure in an electric brake booster;

FIG. 10 is a schematic view of another possible embodiment of a pedal spring limit structure in an electric brake booster;

FIG. 11 is a schematic view of a possible embodiment of a stop lock (in a locked state) in an electric brake booster;

FIG. 12 is a schematic view of the stop lock of FIG. 11 in a stop release state;

FIG. 13 is a schematic view of another possible embodiment of a stop lock (in a locked state) in an electric brake booster;

FIG. 14 is a schematic view of a rocker in the stop lock of FIG. 13;

FIG. 15 is a schematic view of the stop lock of FIG. 14 in a stop release state;

FIG. 16 is a schematic illustration of yet another possible embodiment of a stop lock (in a locked state) in an electric brake booster;

FIG. 17 is a schematic view of the stop lock of FIG. 16 in a stop released state.

Detailed Description

Some possible embodiments of the present application are described below with reference to the drawings. It is to be noted that the drawings are designed solely to embody the principles of the present application and not to represent actual structures of the present application. Accordingly, the drawings are not to scale; also, some details are exaggerated and some details are omitted for clarity.

It is first of all pointed out that in the present application, "rear side" means the side which is kinematically close to the brake pedal of the vehicle, and "front side" means the side which is kinematically facing away from the brake pedal, i.e. close to the master cylinder.

As shown in fig. 1 and 2, an electric brake booster for a vehicle brake system according to one possible embodiment of the present application is used to transmit an output force to a piston 2 of a master cylinder 1 of a vehicle hydraulic brake system. Some structural details of the electric brake booster are shown in fig. 3-10. Fig. 1 and 2 show the home position (non-operating state) of the electric brake booster.

The piston 2 is axially movable relative to the cylinder body of the master cylinder 1. The master cylinder 1 and its piston 2 of a hydraulic vehicle brake system are common in the art and will not be described in detail. Note that the master cylinder 1 has a double piston, the piston 2 is shown as a rear chamber (first chamber) piston of the master cylinder 1, and the master cylinder 1 further includes a front chamber (second chamber) piston, not shown.

The electric brake booster of the present application is associated with the brake pedal side presser 3, and includes a brake motor 4 for generating brake assist. The electric brake booster further includes a control unit 5 and a pedal stroke sensor 6. The pedal stroke sensor 6 is for detecting the stroke of the pushing member 3, that is, the stroke of the brake pedal. The control unit 5 is capable of receiving a brake pedal stroke signal detected by the pedal stroke sensor 6, and of controlling the operation of the brake motor 4. The control unit 5 activates the brake motor 4 to generate the brake assist pressure upon receiving the brake signal. The braking signal may be a brake pedal travel signal or a braking signal from an automatic vehicle braking function.

In the case of performing braking with the brake motor 4, only the brake assist force generated by the brake motor 4 is used as the input force of the electric brake booster, which does not include the pedal force from the brake pedal. In the case where braking is performed without using the brake motor 4, for example, the brake motor 4 is not supplied with electric power, or the brake motor 4 is disabled, the pedal force input by the driver through the brake pedal via the pushing member 3 may be used as the input force of the electric brake booster.

The electric brake booster further comprises a transmission sleeve 11 and a drive nut 12, both arranged coaxially with the piston 2 and thus defining a central axis of the electric brake booster. The transmission sleeve 11 is arranged in the drive nut 12 with a threaded transmission fit between the two. The drive nut 12 is rotatably arranged in a booster housing (not shown) by means of a bearing 13 (and possibly other bearings). The brake motor 4 rotates the drive nut 12 via a corresponding transmission mechanism (e.g., a gear train). In the case of an electrically charged brake motor 4, the brake motor 4 can lock the axial position of the drive nut 12 by means of a transmission (in particular a gear train) between it and the drive nut 12, so that the drive nut 12 cannot be moved axially. Under the condition that the brake motor 4 is not electrified, as the motor rotor can rotate freely, the axial movement locking function of the brake motor 4 on the drive nut 12 is released, and the drive nut 12 can move axially.

Alternatively, a separate locking structure may be provided. In the case where the brake motor 4 is electrically charged, the locking structure locks the drive nut 12 axially, and thus the drive nut 12 does not have axial displacement capability. And in the case where the brake motor 4 is not charged, the locking structure unlocks the axial movement of the drive nut 12 so that the drive nut 12 can move axially.

In the case of an axially locked drive nut 12, rotation of the drive nut 12 may force the transmission sleeve 11 to move axially in the drive nut 12.

Referring to fig. 5, the drive nut 12 is generally cylindrical with an axial section being a thread section 12a provided with inwardly facing threads for engagement with the external threads of the transmission sleeve 11 (the transmission sleeve 11 may be provided with external threads over its entire length). In addition, the thread section 12a divides the inner bore of the drive nut 12 into a front section 12b and a rear section 12 c. The axial length of the thread segments 12a is about 1/3 or less of the axial length of the drive nut 12. The forward section 12b preferably has a smaller axial length than the rearward section 12 c.

Returning to fig. 1, 2, between the transmission sleeve 11 and the piston 2, a plunger 14 is arranged. The driving force generated by the brake motor 4, i.e. the braking assistance force, can be transmitted to the transmission sleeve 11 via the drive nut 12 and then from the transmission sleeve 11 to the piston 3 via the plunger 14. The plunger 14 and the piston 2 can be directly pushed against each other, so that the plunger 14 can directly transmit the braking assistance to the piston 2. Alternatively, a force transmission element (e.g. a ram) may be arranged between the plunger 14 and the piston 2, such that the plunger 14 transmits the braking assistance force to the piston 2 via the force transmission element. The arrangement of such force transmitting elements may facilitate the distribution of the braking assistance over the piston 2, etc.

Referring to fig. 6, the plunger 14 has a front end wall 14a, a pair of flanges 14b projecting in diametrically opposite directions from diametrically opposite sides of the front end wall 14a, and a body projecting rearward from the outer periphery of the front end wall 14 a. The body includes a generally cylindrical first section 14c joined to the front end wall 14a, and a generally cylindrical second section 14d projecting upwardly from the rear edge of the first section 14 c. In the body, a radial through hole (inner cavity) 14e penetrating the body is formed in a radial direction perpendicular to a radial direction in which the flange 14b extends. The front end of the radial through hole 14e terminates in a front end wall 14a, and the rear end of the radial through hole 14e communicates with the rear end face of the body through an axial through hole 14 f. Further, in the first section 14c, at least one positioning hole 14g (two shown diametrically opposite to each other) is formed through the first section 14 c. Further, a protruding portion 14h extending rearward is formed on the rear surface of each flange 14 b.

The front end of the push rod 15 is connected with a pedal spring 16. The pedal spring 16 may include a combination spring in which spring pieces are stacked such that the spring rate of the pedal spring 16 in the axial direction gradually increases from the longitudinal (radially) outer end toward the radial center. For example, referring to fig. 7, the pedal spring 16 includes

spring pieces

16a, 16b, 16c stacked in order in the axial direction. The radial dimension of each spring piece is gradually reduced from the axial front side to the axial rear side.

Returning to fig. 1 and 2, the front end of the plunger 14 is configured and adapted to push against the piston 2 (directly or indirectly). The second section 14d of the plunger 14 is inserted into the front section 12b of the drive nut 12 such that the plunger 14 is axially movable relative to the drive nut 12.

A push rod 15 is arranged in the axial through hole defined by the transmission sleeve 11. The front end of the pushing component 3 is connected with a push rod 15. The front portion of the push rod 15 protrudes from the front end of the transmission sleeve 11, and is inserted into the radial through hole 14e through the axial through hole 14f of the plunger 14. The forward end of the push rod 15 is also connected to a reaction plate 17 located forward of the pedal spring 16. The pedal spring 16 and the reaction plate 17 are exposed from both sides in the radial direction of the plunger 14 through the radial through hole 14e of the plunger 14. In the home position, the reaction plate 17 is located axially rearward of the front end wall 14a of the plunger 14 and is spaced an axial distance from the front end wall 14 a.

The pedal spring 16 is connected at its radial ends to respective limit rods 18. The stopper rod 18 extends parallel to the booster central axis and is restrained by a stopper plate 19 arranged around the second section 14d of the plunger 14, so that the stopper rod 18 can move back and forth over a limited axial distance relative to the stopper plate 19. In the example shown in fig. 8, the front end of the stopper rod 18 is fixed to the longitudinally outer end of the pedal spring 16, and the rear portion of the stopper rod 18 is formed with a thin rod portion 18a, which thin rod portion 18a is inserted into a through hole 19a in the corresponding radial end portion of the stopper plate 19 shown in fig. 9 and is axially movable in the through hole 19 a. When the pedal spring 16 is axially elastically deformed by the push rod 15, the axial movement range of the stopper rod 18, that is, the axial movement range of both ends in the radial direction of the pedal spring 16, is limited by the abutment between the large-diameter portions of both ends in the axial direction of the thin rod portion 18a and the end surfaces of both sides in the axial direction of the stopper plate 19. Therefore, the stopper rod 18 and the stopper plate 19 constitute a stopper structure of the pedal spring 16.

It will be appreciated that other forms of pedal spring limiting elements may be employed. For example, fig. 10 shows another stopper structure of the pedal spring 16, in which a front end of a stopper rod 18 is hinged to a longitudinally outer end of the pedal spring 16, and a rear end of the stopper rod 18 is provided with a hinge shaft inserted into a guide groove 19a extending parallel to an axial direction in a stopper plate 19 so that the hinge shaft can move back and forth in the guide groove 19 a. In situ, the radial distance between the front ends of the two restraint rods 18 and the radial distance between the rear ends of the two restraint rods 18 may be different or the same. When the push rod 15 pushes the pedal spring 16 forward, the rear hinge shaft of the stopper rod 18 slides forward in the guide groove 19 a. When the rear end hinge shaft of the stopper rod 18 reaches the front groove bottom of the guide groove 19a, the rear end of the stopper rod 18 is restrained from further advancing, and therefore, the both ends in the radial direction of the pedal spring 16 cannot further advance. As the push rod 15 pushes the middle portion of the pedal spring 16 forward, the pedal spring 16 starts to elastically deform in the axial direction.

The retainer plate 19 is non-rotatable and remains in a constant axial position with the drive nut 12. In other words, the limit plate 19 is axially movable with the drive nut 12, but is not rotatable. The above-described capability of the stopper plate 19 can be achieved by an appropriate holding structure. For example, in the illustrated example, the stopper plate 19 is fixed to the outer ring of the bearing 13.

Spring pressing pieces 20 for pressing first return springs 21 are installed on the front sides of both ends in the radial direction of the reaction plate 17. The first return spring 21 serves to urge the push rod 15 axially rearward via the spring pressure piece 20, the reaction plate 17, and the pedal spring 16. The first return spring 21 may be installed between the cylinder body of the master cylinder 1 and the spring pressure block 20.

Further, a second return spring 22 is interposed between the cylinder body of the brake master cylinder 1 and the flange 14b of the plunger 14 for urging the plunger 14 axially rearward. The second return spring 22 has a spring rate greater than that of the first return spring 21.

It is understood that the first return spring 21 and the second return spring 22 may be disposed at other positions according to the internal structure of the booster. In the illustrated example, both are in the form of helical compression springs, but other types of springs may be employed as long as the above-described pressing functions of both can be achieved. For example, in the example shown in fig. 10, the first return spring 21 is a 3D wire spring, one end of which is hooked to the longitudinally outer end of the pedal spring 16, and the other end of which is fixed to the stopper plate 19. It will be appreciated that the second return spring 22 may also take the form of a 3D wire spring.

In addition, at least one (two shown diametrically opposite each other) stop lock 30 is mounted on the plunger 14. One possible configuration of the stop lock 30 is shown in fig. 2, 11 and 12, wherein the stop lock 30 includes a solenoid 31 secured to the plunger 14 (e.g., to the protruding portion 14h of the plunger 14) outside the first segment 14c, the solenoid 31 defining a receptacle therein that is aligned with the positioning aperture 14g of the plunger 14. The stopper lock 30 further includes a stopper pin 32, and the stopper pin 32 is made of a magnet and includes an outer rod portion 32a and an inner rod portion 32b that are coaxial with each other, and a flange portion 32c between the outer rod portion 32a and the inner rod portion 32 b. The diameters of the outer rod portion 32a and the inner rod portion 32b may be the same or different. The outer rod portion 32a is slidably inserted in the insertion hole of the electromagnetic coil 31, and the inner rod portion 32b is slidably inserted in the positioning hole 14g of the plunger 14. A return compression spring 33 is disposed in the insertion hole of the electromagnetic coil 31 between the outer end of the outer rod portion 32a and the outer wall of the electromagnetic coil 31 for applying a radially inward urging force to the stopper pin 32. In a state where the electromagnetic coil 31 is not energized, the stop pin 32 is pushed radially inward by the compression spring 33 so that the flange portion 32c is pushed against the outer surface of the first section 14c and the inner end of the inner rod portion 32b projects into the radial through hole 14e of the plunger 14, as shown in fig. 2, 11, with the stop lock 30 in a stop state such that a portion of the inner rod portion 32b faces the front side of the reaction plate 17. In a state where the electromagnetic coil 31 is energized, the electromagnetic coil 31 generates a magnetic field that generates a radially outward attracting force to the stopper pin 32, which overcomes the urging force of the compression spring 33, so that the stopper pin 32 is moved radially outward until the flange portion 32c is urged against the inner end of the electromagnetic coil 31 and the inner end of the inner rod portion 32b is retracted into the radial through hole 14e of the plunger 14, as shown in fig. 12, at which time the stopper lock 30 is in a stopper released state with the inner rod portion 32b completely moved away from a position facing the front side of the reaction plate 17.

It will be appreciated that the stop lock 30 may take a variety of forms to accommodate the space around the outer periphery of the plunger 14. For example, in another possible embodiment shown in fig. 13-15, the stop lock 30 includes a solenoid 31 secured outside the first section 14c of the plunger 14. The stop lock 30 further comprises a stop pin 32, the stop pin 32 being made as a substantially cylindrical body from a magnet. One part is slidably inserted into the insertion hole of the electromagnetic coil 31, and the other part is slidably inserted into the positioning hole 14g of the plunger 14. The stop lock 30 further includes a rocker 34 having a serpentine or curvilinear shape including a front section 34a and a continuous rear section 34 d. A guide groove 34c is formed in the front section 34a, and a positioning pin 35 fixed to the stopper pin 32 is inserted into the guide groove 34c and is slidable in the guide groove 34 c. The rear end of the front section 34a is supported by the pin shaft 36 on a portion of the plunger 14, which faces the outer periphery of the stopper pin 32. Thus, when the stop pin 32 moves in the booster radial direction, the positioning pin 35 swings the swing link 34, and the position of the stop pin 32 in the radial direction can be defined by the swing link 34 abutting the outer periphery of the plunger 14 or abutting the inner end of the electromagnetic coil 31. In order to achieve a secure abutment between the rocker 34 and the inner end of the solenoid 31, a bevel 34d is formed on the front section 34a facing the solenoid 31, so that the bevel 34d can abut against the inner end face of the solenoid 31 when the stop pin 32 is moved into the solenoid 31. A return compression spring 33 is disposed in the insertion hole of the electromagnetic coil 31 between the outer end of the stopper pin 32 and the outer wall of the electromagnetic coil 31 for applying a radially inward urging force to the stopper pin 32.

According to another embodiment shown in fig. 16, 17, the stop lock 30 comprises a solenoid 31 fixed outside the first section 14c of the plunger 14. The stop lock 30 further comprises a stop pin 32, the stop pin 32 being made as a substantially cylindrical body from a magnet. One part is slidably inserted into the insertion hole of the electromagnetic coil 31, and the other part is slidably inserted into the positioning hole 14g of the plunger 14. The catch lock 30 further comprises a spring plate 37 and a channel 38. The channel 38 has a transverse slot, the channel 38 being fixed to the stop pin 32 with its slot facing away from the stop pin 32, into which slot the front end of the spring plate 37 is inserted. The rear section of the spring piece 37 is fixed to a portion of the plunger 14, which faces the outer periphery of the stopper pin 32. The spring piece 37 is used to apply a radially inward urging force to the stopper pin 32 via the groove piece 38, so that when the electromagnetic coil 31 is not energized, the spring piece 37 urges the stopper pin 32 in a stopper state in which the groove piece 38 is urged against the outer periphery of the first section 14c of the plunger 14. When the electromagnetic coil 31 is not energized, the electromagnetic coil 31 attracts the stopper pin 32 to move radially outward against the urging force of the spring piece 37 until the stopper pin 32 pushes against the inner end of the electromagnetic coil 31, so that the stopper lock 30 reaches the stopper released state. In the present embodiment, the return compression spring 33 in the previous embodiment is eliminated.

Other forms of stop locks 30 may be devised by those skilled in the art based on the principles of the present application.

Regardless of the specific form of the stopper lock 30, in the home position of the electric brake booster shown in fig. 1 and 2, when the stopper lock 30 is in the stopping state, a portion of the stopper pin 32 (the portion that protrudes into the radial through hole 14e, i.e., the inner cavity, of the plunger 14) is located on the front side of the reaction plate 17, and the axial distance between the portion of the stopper pin 32 and the front side of the reaction plate 17 is half or less, preferably 1/3 or less, for example, less than 3mm, preferably less than 2mm, of the axial movement range of the stopper rod 18 that is limited by the stopper plate 19.

The operation of the stopper lock 30 is associated with the brake motor 4. With the brake motor 4 powered up, the solenoid 31 of the stop lock 30 is energized; with the brake motor 4 powered down, the solenoid 31 of the stop lock 30 is de-energized.

Fig. 3 schematically depicts a pedal force transmission mechanism (line) in the electric brake booster, in which pedal force can be transmitted to the pedal spring 16, the reaction plate 17 via the push piece 3, the push rod 15, so that the pedal spring 16, the reaction plate 17 can move forward against the first return spring 21. A radially extending section 17a is mounted or formed at one end of the reaction plate 17 in the radial direction, the radially extending section 17a facing the pedal stroke sensor 6, so that the axial movement of the radially extending section 17a can be detected by the pedal stroke sensor 6 (e.g. by a varying magnetic field), whereby the control unit 5 can determine the pedal stroke, and thus the braking intention of the driver.

Fig. 4 schematically depicts a brake assist transmission mechanism (line) in the electric brake booster, in which the driving force (brake assist) of the brake motor 4 is transmitted to the plunger 14 through the drive nut 12, the transmission sleeve 11, so that the plunger 14 is moved forward against the urging force of the second return spring 22, and the plunger 14 transmits the brake assist generated by the brake motor 4 to the piston 2 as the output force of the electric brake booster.

It is to be noted that in the example shown, the braking assistance is transmitted mainly through the drive nut 12 and the transmission sleeve 11; however, it is understood that other mechanisms for converting rotational motion into linear motion, such as rack and pinion mechanisms and the like, may be used herein to transmit braking assistance.

Furthermore, it should be noted that the plunger 14, the push rod 15, the pedal spring 16, the reaction plate 17 are only allowed to move axially, but not to rotate, and their rotation prevention can be achieved by suitable constraint structures, for example by a limit plate 19 (non-rotatable) through the rotation prevention constraint of the pedal spring 16 by a limit rod 18.

The operation of the electric brake booster is described below.

The normal operation mode of the electric brake booster is first described. The so-called normal operation is that the electric brake booster is started based on the action of the driver depressing the brake pedal, and the brake assist is provided by the brake motor 4. Before the driver depresses the brake pedal, the brake motor 4 is not powered and the stop lock 30 is in the stop state. After the driver depresses the brake pedal, the pushing member 3 pushes the pedal spring 16 and the reaction plate 17 axially forward via the push rod 15. Since there is a small axial distance between the front surface of the reaction plate 17 and the stopper pin 32, within which the control unit 5 detects the above-mentioned actions of the pedal spring 16 and the reaction plate 17 through the pedal stroke sensor 6, thereby confirming that the driver depresses the brake pedal, and thus starts the brake motor 4 to rotate forward to drive the plunger 14 to move forward by a certain distance, and at the same time, energizes the solenoid 31 of the stopper lock 30, so that the stopper pin 32 is retracted radially outward, and the stopper lock 30 reaches the stopper release state without blocking the reaction plate 17, so that the stopper lock 30 does not obstruct the operation of the pedal force transmission line, and the driver can continue to depress the brake pedal, and the plunger 14 continues to advance, resulting in the piston 2 moving forward into the cylinder of the master cylinder 1, and thus initially building up pressure in the cylinder of the master cylinder 1. The brake pedal is depressed at this stage to make a lost motion.

After the idle stroke is finished, if the driver further steps on the brake pedal, the limiting rod 18 is limited by the limiting plate 19 and cannot move continuously, the two ends of the pedal spring 16 are limited by the limiting rod 18 and cannot move forward further axially, the pedal spring 16 starts to deform axially, the pedal spring 16 generates gradually increased reaction force transmitted to the brake pedal, and meanwhile, the reaction plate 17 moves forward further. The control unit 5 detects the further forward movement by the pedal stroke sensor 6 and thus determines the driver's braking intention, thereby controlling the brake motor 4 to rotate in the forward direction to drive the plunger 14 to move further forward by a determined distance. This section of the plunger 14 moves forward, causing the piston 2 to move further forward into the cylinder of the master cylinder 1, so that the brake fluid pressure of the master cylinder 1 increases abruptly, i.e., the pressure jumps. The master cylinder 1 outputs brake fluid of increasing pressure to a braking element of a brake system, thereby braking the vehicle. Thereafter, a booster phase is entered, in which the pressure-force curve between the output pressure of the master cylinder 1 and the booster has a high slope to provide a rapid increase in the non-output pressure.

At the end of braking, the driver releases the brake pedal, the reaction plate 17 moves backwards under the hydraulic pressure in the brake master cylinder 1 and the urging of the first return spring 21, the control unit 5 thus judges the intention of the driver to end braking, and drives the brake motor 4 to rotate in reverse, so that the transmission sleeve 11 returns to the home position, the reaction plate 17, the pedal spring 16 and the push rod 15 return to the home position under the action of the first return spring 21, and the plunger 14 also returns to the home position under the action of the second return spring 22. Then, the brake motor 4 is powered down, the stop lock 30 is powered off, and the stop state is returned.

In the normal operation mode of the electric brake booster of the present application, on the one hand, the booster provides a booster curve similar to a conventional vacuum booster, and therefore, the vacuum booster can be replaced and a similar boosting function provided. On the other hand, the pedal reaction force and the stroke that the driver feels on the brake pedal are similar to those in the conventional brake pedal operation.

The electric-only operating mode of the electric brake booster is described next. The so-called electric-only operating mode is when the driver does not depress the brake pedal, the control unit 5 activates the electric brake booster on the basis of the brake signal from the automatic vehicle braking function, or the automatic vehicle braking function takes over the electric brake booster directly. In this case, the push rod 15, the pedal spring 16 and the reaction plate 17 are kept stationary, and the control unit 5 controls the brake motor 4 to rotate in the forward direction to drive the plunger 14 to move forward through the driving nut 12 and the transmission sleeve 11 to push the piston 2 forward, thereby achieving vehicle braking. At the same time, the solenoid 31 of the stopper lock 30 is energized, so that the stopper lock 30 reaches the stopper released state. When it is determined that braking is finished, the brake motor 4 is controlled to rotate reversely so that the transmission sleeve 11 is returned to the home position, and the plunger 14 is also returned to the home position by the second return spring 22. Then, the brake motor 4 is powered down, the stop lock 30 is powered off, and the stop state is returned.

The input force of the electric brake booster comes only from the brake motor 4 without any pedal force component, regardless of the normal operation mode or the electric-only operation mode. Thus, these two braking modes may be collectively referred to as motor braking operation. Also, a similar boost ratio and boost profile to a conventional vacuum booster can be provided, whether in the normal or pure electric mode of operation. Furthermore, the pedal stroke applied by the driver is used by the control unit 5 for determining the driver's braking intention only in the normal operation mode. In the normal operation mode, the driver's braking experience is similar to a conventional braking system, including a conventional brake system with a vacuum booster, due to the deformation of the pedal spring 16, resulting in a gradually increasing reaction force being fed back to the driver's foot via the brake pedal.

Furthermore, the electric brake booster has a pure pedal operating mode. The pure pedal operation mode occurs when the brake motor 4 is not functioning properly, or is disabled, in which case the brake motor 4 is not being supplied with electrical energy. At this time, the stopper lock 30 is in the stopper state, and the axial movement locking function of the drive nut 12 is released, and thus, it can move axially. When the driver depresses the brake pedal, the push element 3 pushes the pedal spring 16 axially forward via the push rod 15, and due to the small axial distance between the reaction plate 17 and the stop pin 32, the reaction plate 17 is pushed against the stop pin 32 of the stop lock 30 in a short time and thus by bringing the plunger 14 forward, thereby pushing the piston 2 forward to apply the vehicle brake. As the push rod 15 is further advanced, the pedal spring 16 will pull the limit plate 19 via the limit rod 18, and the limit plate 19 with the driving nut 12 and the transmission sleeve 11 is also axially advanced. After braking is finished, the related elements return to the original positions under the action of the first return spring 21 and the second return spring 22.

In addition, electric brake boosters, when used in electric vehicles, also have the ability to participate in the recovery of braking energy. In the braking energy recovery operation, the control unit 5 detects depression of the brake pedal and controls the brake motor 4 to drive the plunger 14 to move forward by a set distance. At the same time, the solenoid 31 of the stopper lock 30 is energized, so that the stopper lock 30 reaches the stopper released state.

According to the application, when the motor braking operation is performed, the stop lock is released, so that the brake boosting transmission line is decoupled relative to the pedal force transmission line. The action of the brake assist force transmitting element does not pull the pedal force transmitting element and the brake pedal, whereby the driver can be prevented from receiving an unpleasant feeling from the brake pedal. Further, when the brake motor is operated, the input force of the electric brake booster is derived only from the brake motor without combining the pedal force.

In the case where the brake motor is normally operated, the pedal spring is used as a braking behavior simulator for providing a tactile sensation for feedback of the braking state to the driver's foot and for judging the driver's intention to brake, and the pedal force is not converted into a part of the output force of the brake booster. On the other hand, when the pure pedal braking operation is performed, the stop lock is in the stop state, so that the pedal force transmission element can drive the brake boosting force transmission element through the stop lock, and therefore, the idle stroke of the pedal force transmission element is reduced, and the rapid vehicle braking is realized.

Furthermore, the electric brake booster according to the invention is particularly suitable for vehicles with an automatic braking function, i.e. the control of the electric brake booster and the vehicle brake system is taken over by the automatic braking function, without the driver having to depress the brake pedal.

It should be noted that although the present application has been described and illustrated herein with reference to particular embodiments, the scope of the present application is not limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims

1. An electric brake booster for use in a vehicle, comprising:

a pedal force transmitting element configured to transmit a pedal force from a brake pedal;

a brake motor (4) configured to perform a motor braking operation to generate a brake assist force;

a power-assist transmission element configured to axially push a piston (2) of a master cylinder (1); and

a stopper lock (30) provided on the power transmission element and configured to switch between a stopper state and a stopper release state;

wherein the electric brake booster has a motor braking mode of operation and a pure pedal braking mode of operation;

in the motor brake mode of operation, the stop lock is placed in a stop-released state, such that the pedal-force transmission element and the power-assist transmission element are kinematically decoupled, only the brake power generated by the brake motor being transmitted via the power-assist transmission element to the piston of the brake master cylinder;

in the pure pedal brake operating mode, the stop lock is placed in the stop state, so that the pedal force is transmitted via the pedal force transmission element, the stop lock and the power-assisted transmission element to the piston of the brake master cylinder.

2. The electric brake booster of claim 1, wherein the motor braking operation includes:

a normal braking operation in which the brake motor (4) is activated based on the detected action of the pedal force transmitting element, so that the brake motor (4) is rotated in the forward direction to generate a braking assist force; and

and pure electric operation, wherein the brake motor (4) is started based on a brake signal of the automatic brake module of the vehicle, so that the brake motor (4) rotates forwards to generate brake assistance.

3. The electric brake booster according to claim 1 or 2, wherein the state of the stop lock (30) is associated with a charging state of the brake motor (4); when the brake motor (4) is powered on, the stop lock (30) is placed in a stop release state; when the brake motor (4) is powered down, the stop lock (30) is placed in a stop state.

4. An electric brake booster according to any one of claims 1 to 3, wherein the boost transfer element comprises a drive nut (12) configured to be driven in rotation by a brake motor and a transmission sleeve (11) coupled to the drive nut to convert the rotational movement of the drive nut into an axial linear movement;

the power transmission element further comprises a plunger (14) arranged axially between the piston (2) of the master brake cylinder (1) and the transmission sleeve (11), said plunger being configured and adapted to be pushed axially forward by the transmission sleeve (11) towards the cylinder of the master brake cylinder (1).

5. The electric brake booster of claim 4, wherein the pedal force transmitting element includes:

a push rod (15) arranged in the transmission sleeve (11) and capable of sliding axially in the transmission sleeve, the rear part of the push rod is driven by a brake pedal, and the front part of the push rod extends into an inner cavity (14d) of the plunger (14);

a pedal spring (16) supported by a front portion of the push rod (15) and radially protruding from the inner cavity (14d), the pedal spring (16) having a capability of elastically deforming in an axial direction under an axial urging action of the push rod (15); and

and a reaction plate (17) supported by the front portion of the push rod (15) at the front side of the pedal spring (16).

6. The electric brake booster according to claim 5, wherein, in the motor brake operation mode, the pedal spring (16) constitutes a brake behavior simulator, the action of which can be detected to judge the driver's brake intention, and which can also provide the driver's foot with a tactile sensation of feedback of the brake state.

7. The electric brake booster according to claim 5 or 6, wherein the stopper lock (30) includes:

an electromagnetic coil (31) fixed to the plunger (14);

a stopper pin (32) made of a magnet configured to be attracted by the electromagnetic coil to move to a stopper release position when the electromagnetic coil is energized; and

a reset feature configured to reset the stop pin to the stop position when the solenoid is de-energized.

8. The electric brake booster of claim 7, wherein, in the stop position, the stop pin moves to the reaction plate front side; in the stop release position, the stop pin is completely displaced from the reaction plate front side.

9. The electric brake booster according to claim 7 or 8, wherein the stopper lock (30) further includes a positioning feature for limiting a position of the stopper pin such that the stopper pin is held at the stopper position or the stopper release position.

10. The electric brake booster of claim 9, wherein the positioning feature is:

a flange portion (32c) provided on the outer periphery of the stopper pin; or

One end of the swing rod (34) is followed by the stop pin, and the other end of the swing rod is hinged to the plunger; or

A spring plate (37) having one end following the stop pin and the other end fixed to the plunger, the spring plate also constituting the reset feature.