JP6379366B2 - Electric booster - Google Patents

Description

  The present invention relates to an electric booster used for a vehicle brake.

  In an electric booster, a stroke sensor that detects an operation amount of a brake pedal, an electric motor (electric actuator) that is controlled based on an operation amount of the brake pedal detected by the stroke sensor, and rotation of the electric motor There is a rotary linear motion conversion mechanism that converts motion into a linear motion of a ball screw shaft, and a piston (primary piston) is propelled by a linear motion member of the rotary linear motion conversion mechanism. In this type of electric booster, the piston can be directly moved by an input member (input rod) that moves in accordance with the operation of the brake pedal when the electric motor fails (fails). . By the way, in the electric booster, when the input member moves forward by a predetermined distance, i.e., a distance that is likely to reach the assist limit by the electric motor, by operating the brake pedal, the input member abuts on the input member. Japanese Patent Application Laid-Open No. H10-228667 discloses a reaction force application spring that applies a reaction force. The reaction force application spring suppresses a sudden change in the reaction force increase amount with respect to the operation of the brake pedal, thereby improving the operation feeling of the brake pedal.

JP 2012-96649 A

  In the electric booster described in Patent Document 1, for example, when the brake pedal is depressed to advance the piston when the electric motor fails, it is necessary to crush the reaction force application spring. As a result, the operating force (stepping force) for compressing the vehicle increases, and as a result, the burden on the driver increases.

  Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide an electric booster capable of reducing the depressing force of a brake pedal when an electric motor or the like fails. .

In order to solve the above-described problems, an electric booster according to the present invention includes a piston having a distal end disposed in a cylinder body of a master cylinder and forming a pressure chamber with the cylinder body, and an electric motor that drives the piston. An actuator, an input member connected to a brake pedal, and an input member connected to the input member and disposed so that the tip side faces the pressure chamber, and can move relative to the piston in a direction along the axis of the piston. An input piston provided, and a pair of reaction force adjustment springs that elastically hold the input piston at an intermediate position in the direction along the axis with respect to the piston, and the pressure of the pair of reaction force adjustment springs A chamber-side spring is disposed in a liquid chamber formed between the piston and the input piston, and the brake pedal is not operated by the piston. From the non-braking position of the piston is, until near the boosting limit position of the piston assisting by the electric actuator is the limit, the communication passage is provided for communicating the liquid chamber to the reservoir of the master cylinder, the The communication path is characterized in that communication with the reservoir is blocked when the piston is located in a section where the brake pedal is further depressed from the assist limit position .

  ADVANTAGE OF THE INVENTION According to this invention, the electric booster which can reduce the depressing force of the brake pedal at the time of a failure can be provided.

It is sectional drawing by the uniaxial plane of the electric booster of this embodiment. It is a principal part enlarged view of the cross section by the uniaxial plane of the electric booster of this embodiment, Comprising: It is a figure which shows the non-operation state of a brake pedal especially. It is a principal part enlarged view of the cross section by the uniaxial plane of the electric booster of this embodiment, Comprising: It is a figure which shows the state which a primary piston is especially located in the assist limit position vicinity. It is a principal part enlarged view of the cross section by the uniaxial plane of the electric booster of this embodiment, Comprising: It is a figure which shows the state at the time of regenerative braking especially. It is a principal part enlarged view of the cross section by the uniaxial plane of the electric booster of this embodiment, Comprising: It is a figure which shows the state located in the area where the primary piston exceeded the assistance limit position especially.

  An embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, for the sake of convenience, the left side (left direction) and the right side (right direction) in FIG. 1 are defined as the front side (front direction) and the rear side (rear direction) of the electric booster 1.

  As shown in FIG. 1, the electric booster 1 includes a tandem master cylinder 2, a housing 4 that houses an electric motor 3 (electric actuator), and a reservoir 5 connected to the master cylinder 2. . The housing 4 is coupled to the right end (opening side) of a substantially bottomed cylindrical cylinder body 6 of the master cylinder 2. The electric booster 1 is arranged in the engine room of the vehicle, and a dash panel is provided by a plurality of stud bolts 8 erected on a mounting seat 7 on the opposite side (right side) of the housing 4 to the master cylinder 2 side. Fixed to.

  The electric booster 1 includes a primary piston 10 (piston) whose left side (front end side) is disposed in the cylinder body 6 of the master cylinder 2 and forms a primary chamber 9 (pressure chamber) with the cylinder body 6; A secondary piston 12 disposed on the left side (bottom side) of the cylinder body 6 and forming a secondary chamber 11 with the cylinder body 6; The primary chamber 9 and the secondary chamber 11 are provided with hydraulic ports 13 and 14, respectively. The hydraulic ports 13 and 14 are connected to two systems of hydraulic circuits (not shown) for supplying hydraulic pressure to the brake calipers of the respective wheels of the vehicle.

  The cylinder body 6 of the master cylinder 2 is provided with a reservoir port 15 for communicating the primary chamber 9 and the reservoir 5 and a reservoir port 16 for communicating the secondary chamber 11 and the reservoir 5. The cylinder bore 17 of the cylinder body 6 and the primary piston 10 are sealed by a pair of seal members 18A and 18B. The cylinder bore 17 and the secondary piston 12 are sealed by a pair of seal members 19A and 19B.

  When the brake pedal is not operated, that is, when the primary piston 10 is located in the non-braking position (see FIG. 2), the primary chamber 9 is connected to the reservoir port 15 via the port 20 provided in the primary piston 10; As a result, it communicates with the reservoir 5. In the primary chamber 9, when the primary piston 10 moves forward from the non-braking position, the port 20 is sealed by the seal member 18 </ b> A, and the communication with the reservoir port 15 and thus the reservoir 5 is blocked.

  On the other hand, the secondary chamber 11 has a reservoir port via a port 21 provided in the secondary piston 12 when the brake pedal is in a non-operating state, that is, when the secondary piston 12 is located in the non-braking position (see FIG. 2). 16 and eventually communicated with the reservoir 5. Further, in the secondary chamber 11, when the secondary piston 12 moves forward from the non-braking position, the port 21 is sealed by the seal member 19A, and the communication with the reservoir port 16 and thus the reservoir 5 is blocked.

  The primary chamber 9 is provided with a spring assembly 22 interposed between the primary piston 10 and the secondary piston 12. The secondary chamber 11 is provided with a return spring 23 (compression coil spring) interposed between the bottom of the master cylinder 2 and the secondary piston 12. The spring assembly 22 includes a retainer 25 that holds the compression coil spring 24 so as to be extendable and contractible. The primary piston 10 includes an intermediate wall 26 that divides the inside of a front side portion formed in a cup shape and a rear side portion formed in a cylindrical shape in the front-rear direction.

  The electric booster 1 has an input rod 27 (input member) connected to a brake pedal, and an input piston 29 connected to the input rod 27 via a plunger 28. The input piston 29 is disposed so that the front side (tip side) faces the primary chamber 9 (pressure chamber), and is slidably and liquid-tightly inserted into a bore 30 provided in the intermediate wall 26 of the primary piston 10. It has a portion 29A, a piston portion 29B that is slidably and liquid-tightly fitted to the inner periphery of the rear portion of the primary piston 10, and a shaft portion 29C that is in contact with the plunger 28. The input piston 29 can be moved relative to the primary piston 10 in the front-rear direction, that is, in the direction along the axis of the primary piston 10 by the shaft portion 29A.

  The input piston 29 is elastically held by the pair of reaction force adjusting springs 31 and 32 at a middle position (see FIG. 1) in the front-rear direction, that is, in the direction along the axis of the primary piston 10 with respect to the primary piston 10. . The front reaction force adjusting spring 31 is interposed between the intermediate wall 26 of the primary piston 10 and the spring receiving portion on the front side of the piston portion 29B. The rear reaction force adjusting spring 32 is interposed between a spring receiving portion on the rear side of the piston portion 29 and a spring receiving member received by a front end surface of a linear motion member 35 of a ball screw mechanism 34 described later. The

  The housing 4 includes a ball screw mechanism 34 that is driven by the electric motor 3 (electric actuator) via the transmission mechanism 33. The ball screw mechanism 34 is supported by a hollow shaft type linear motion member 35 (ball screw shaft) and a pair of bearings 39 and 40 which are externally provided on the linear motion member 35 and provided in the housing 4 so as to be rotatable around the axis. A cylindrical rotary member 36 (nut), a spirally extending screw groove 37 formed on the outer peripheral surface of the linear motion member 35, and an inner peripheral surface of the rotary member 36 corresponding to the screw groove 37. A screw groove 38 extending in a spiral shape and a plurality of balls (steel balls) arranged between the screw grooves 37 and 38 are provided.

  In the ball screw mechanism 34, the linear motion member 35 is urged rearward (retreat side) by a return spring 42 (compression taper coil spring) interposed between the housing 4 and the ring-shaped spring receiving member 41. Further, the rear end of the primary piston 10 is received by the front end of the linear motion member 35 via the bottom of the spring receiving member 41. Thereby, the electric booster 1 converts the rotational motion of the rotor shaft of the electric motor 3 into the linear motion of the linear motion member 35 by the ball screw mechanism 34, and advances the linear motion member 35 of the ball screw mechanism 34. The primary piston 10 can be directly pushed in (directly moved through the spring receiving member 41) by the linear motion member 35 (moved in the forward direction).

  The electric booster 1 includes an annular channel 47 formed between the inner periphery of the rear side of the cylinder body 6 of the master cylinder 2 and the outer periphery of the primary piston 10, and the annular channel 47 provided in the cylinder body 6. And a communication passage 49 provided on the side wall of the rear side (cylindrical portion) of the primary piston 10 and disposed in the vicinity of the intermediate wall 26. The communication passage 49 is formed between the liquid chamber 50 in which the reaction force adjusting spring 31 on the front side (primary chamber 9 side) is accommodated, in other words, between the intermediate wall 26 of the primary piston 10 and the piston portion 29B of the input piston 29. The internal space on the rear side of the primary piston 10 and the annular flow path 47 on the outer peripheral side of the primary piston 10 are communicated and blocked. A pair of seal members 51A and 51B arranged so as to sandwich the annular flow path 47 is provided on the inner periphery of the master body 2 on the rear side of the cylinder body 6, and the pair of seal members 51A and 51B Both sides in the front-rear direction of the annular channel 47 are sealed against the outer periphery of the primary piston 10. The annular flow path 47, the flow path 48, the communication path 49, the liquid chamber 50, and the seal members 51A and 51B constitute a support limit relative movement prevention mechanism.

  In the present embodiment, the relative position between the annular flow path 47 and the communication path 49 is determined by the electric motor 3 (electric actuator) from the non-operating state of the brake pedal, that is, the non-braking position of the primary piston 10 (see FIG. 2). The annular flow path 47 and the communication path 49 are communicated with each other until the vicinity of the assist limit position of the primary piston 10 where the assist is the limit (immediately before), so that the hydraulic chamber 50 is communicated with the reservoir 5. Is set. Further, the relative position between the annular flow path 47 and the communication path 49 is determined when the primary piston 10 is located in a section where the brake pedal is further depressed from the vicinity of the assist limit position shown in FIG. 3 (the assist limit position of the primary piston 10). (Refer to FIG. 5)), the communication between the annular flow path 47 and the communication path 49 is blocked by the seal member 51A, and the communication between the hydraulic chamber 50 and the reservoir 5 is blocked. .

Next, the operation of this embodiment will be described. Since the primary piston 10 and the secondary piston 12 have substantially the same behavior, only the primary piston 10 will be described for the behavior of the piston.
When the brake pedal is operated, that is, when the brake pedal is depressed, the input piston 29 connected to the input rod 27 through the plunger 28 moves forward. The displacement of the input piston 29 is detected by a stroke sensor. The control device controls the electric motor 3 (electric actuator) based on the detection result of the stroke sensor, that is, the operation amount of the brake pedal, and drives the linear motion member 35 of the ball screw mechanism 34. Thereby, the primary piston 10 (piston) is moved forward to follow the displacement of the input piston 29.

  The hydraulic pressure generated in the primary chamber 9 (pressure chamber) is transmitted to the secondary chamber 11 via the secondary piston 12. The brake fluid pressure generated in the primary chamber 9 and the secondary chamber 11 of the master cylinder 2 is supplied to the brake caliper of each wheel of the vehicle through the fluid pressure ports 13 and 14, thereby generating a braking force. At this time, a part of the hydraulic pressure in the primary chamber 9 is received by the input piston 29, and the reaction force is fed back to the brake pedal via the plunger 28 and the input rod 27. Thereby, a desired braking force can be generated with a predetermined boost ratio.

  It is to be noted that by adjusting the relative position between the input piston 29 and the primary piston 10 and applying the spring force of the reaction force adjusting springs 31 and 32 to the input piston 29 and adjusting the reaction force against the input rod 27, the boost ratio Can be adjusted. In this case, the boost ratio can be increased by adjusting the displacement amount of the primary piston 10 to the front side with respect to the displacement amount of the input piston 29. On the contrary, the boost ratio can be reduced by adjusting the displacement amount of the primary piston 10 to the rear side. As shown in FIG. 4, the primary piston 10 is moved backward with respect to the input piston 29 to reduce the hydraulic pressure in the primary chamber 9, thereby suppressing the braking force due to the hydraulic pressure and the amount of regeneration during regeneration coordination. Can be increased.

  By the way, in the electric booster described in Patent Document 1 described above, when the assist by the electric motor (electric actuator) is the limit, in other words, even when the output of the electric motor 3 reaches the maximum output, Since the primary piston 10 and the input piston 29 are relatively movable in the front-rear direction, when the brake pedal is further depressed from the assist limit of the electric motor 3, only the input piston 29 moves forward with respect to the forward movement of the input rod 27. It is like that.

  This state is a state in which the primary piston 10 is stopped, and the brake pedal is connected via the input piston 29, the plunger 28 and the input rod 27 as the hydraulic pressure in the primary chamber 9 increases with respect to the advance amount (movement amount) of the input piston 29. The ratio of the reaction force increase amount fed back to decreases. As a result, the relationship between the stroke of the brake pedal and the reaction force (pedal depression force) fed back to the brake pedal changes. That is, in the electric booster described in Patent Document 1, when the primary piston 10 reaches the assisting limit position, the rate of increase in the reaction force to the brake pedal is reduced thereafter, so that the depression force of the brake pedal is reduced. Compared to the increase, the pedal stroke increases rapidly, and the rigidity of the brake pedal decreases.

(Normal)
On the other hand, in this embodiment, when the brake pedal is operated and the primary piston 10 moves forward by the driving force of the electric motor 3, and the brake pedal is further depressed from the vicinity of the assisting limit position of the primary piston 10 shown in FIG. As shown in FIG. 5, the assisting limit position of the primary piston 10 is reached. At this time, the communication between the annular channel 47 and the communication passage 49 is blocked, and the communication between the hydraulic chamber 50 and the reservoir 5 is blocked. As a result, the liquid chamber 50 in which the reaction force adjusting spring 31 on the front side (primary chamber 9 side) is accommodated becomes liquid-tight by the brake fluid that is an incompressible fluid, so that the relative movement between the primary piston 10 and the input piston 29 is achieved. Is blocked. That is, when the primary piston 10 reaches the assist limit position, the primary piston 10 moves forward together with the input piston 29. Thereby, it is possible to harmonize the advance amount (movement amount) of the input piston 29 and the reaction force increase amount fed back to the brake pedal, and the assist limit of the electric motor 3 (near the assist limit position of the primary piston 10). When the brake pedal is further depressed, the uncomfortable feeling caused by the decrease in the reaction force increase can be alleviated.

(During regenerative braking)
At the time of regenerative braking as shown in FIG. 4, the hydraulic pressure of the master cylinder 2 is reduced according to the braking amount used for regenerative braking. At this time, since the annular flow path 47 and the communication path 49 are in communication with each other, and the hydraulic chamber 50 and the reservoir 5 are in communication with each other, the primary piston 10 and the input piston 29 are relatively movable. Thereby, the linear motion member 35 and the linear motion member 35 are retracted while the position of the input piston 29 with respect to the cylinder body 6 of the master cylinder 2 remains unchanged.

  In this case, the hydraulic pressure in the primary chamber 9 is reduced by the amount of the reverse movement of the primary piston 10, and is fed back to the brake pedal via the input piston 29, the plunger 28 and the input rod 27 as the hydraulic pressure in the primary chamber 9 decreases. Although the reaction force decreases, as shown in FIG. 4, the reaction force adjustment spring 31 on the front side (primary chamber 9 side) is compressed between the intermediate wall 26 of the primary piston 10 and the piston portion 29 </ b> B of the input piston 29. The As a result, the compressed spring force of the reaction force adjusting spring 31 is fed back to the brake pedal as a reaction force via the input piston 29, the plunger 28 and the input rod 27, and the hydraulic pressure in the primary chamber 9 is applied to regenerative braking. A sense of incongruity due to a decrease in the reaction force when it is lowered can be eliminated.

(At the time of failure)
In the electric booster described in Patent Document 1 described above, when the control by the electric motor becomes impossible due to a failure of the control device, the electric motor, or the ball screw mechanism, the brake pedal is depressed to advance the piston. When this is done, it is necessary to crush a reaction force application spring (compression coil spring) provided on the rear end side of the housing that urges the input rod in the backward direction, and an operating force for compressing the reaction force application spring ( The pedaling force was increased, increasing the burden on the driver.

  On the other hand, in this embodiment, by having the above-mentioned assist limit relative movement prevention mechanism, when the brake pedal is depressed and the piston (primary piston 10) is advanced in the event of failure, the input rod 27 is moved backward. There is no need for a member that crushes the reaction force applying spring to be urged, that is, a resistance to advance the input rod 27. For this reason, compared with the electric booster described in Patent Document 1, it is possible to reduce the operating force (stepping force) of the brake pedal at the time of failure, and to reduce the burden on the driver. it can.

(effect)
According to this embodiment, the brake pedal is not operated, that is, from the non-braking position of the primary piston 10 to the vicinity of the assist limit position of the primary piston 10 where the assist by the electric motor 3 (electric actuator) is the limit. When the fluid pressure chamber 50 is communicated with the reservoir 5 by communicating the annular flow path 47 and the communication path 49 and the primary piston 10 is positioned in a section where the brake pedal is further depressed from the vicinity of the assist limit position, The communication between the fluid pressure chamber 50 and the reservoir 5 was blocked by blocking the communication between the path 47 and the communication path 49.

  Accordingly, when the brake pedal is further depressed from the vicinity of the assist limit position of the primary piston 10, the liquid chamber 50 in which the reaction force adjusting spring 31 on the front side (primary chamber 9 side) is accommodated is closed, and the primary piston 10 and the input piston 29 are closed. Relative movement is prevented. That is, when the primary piston 10 reaches the assist limit position, the primary piston 10 moves forward together with the input piston 29. Thereby, it is possible to harmonize the advance amount (movement amount) of the input piston 29 and the reaction force increase amount fed back to the brake pedal, and the assist limit of the electric motor 3 (near the assist limit position of the primary piston 10). It is possible to relieve the uncomfortable feeling caused by the decrease in the reaction force increase when the brake pedal is further depressed.

  Further, when the brake pedal is depressed and the piston (primary piston 10) moves forward in the event of failure, a reaction force applying spring (compression coil spring) that urges the input rod applied in the conventional electric booster in the backward direction. Therefore, compared with a conventional electric booster, it is possible to reduce the operating force (stepping force) of the brake pedal at the time of failure, and the burden on the driver can be reduced.

  Furthermore, in the invention described in Japanese Patent Laid-Open No. 2013-28273, which is the same as that of the present invention, in order to reduce the advance amount (movement amount) of the input piston 29 with respect to the stroke of the input rod 27, the applicant's stroke However, the degree of increase in the hydraulic pressure of the master cylinder 2 (primary chamber 9) with respect to the operation of the input rod decreases. In this embodiment, the deterioration of the brake pedal operation feeling caused by this is eliminated. Can do.

DESCRIPTION OF SYMBOLS 1 Electric booster, 2 Master cylinder, 3 Electric motor (electric actuator), 5 Reservoir, 6 Cylinder body, 9 Primary chamber (pressure chamber), 27 Input member (input rod), 29 Input piston, 31, 32 Reaction force Adjustment spring, 49 communication path, 50 liquid chamber

Claims (1)

A piston having a tip side disposed in the cylinder body of the master cylinder and forming a pressure chamber with the cylinder body;
An electric actuator for driving the piston;
An input member coupled to the brake pedal;
An input piston that is connected to the input member and is disposed so that a tip side thereof faces the pressure chamber and is relatively movable in a direction along an axis of the piston with respect to the piston;
A pair of reaction force adjustment springs that elastically hold the input piston at an intermediate position in the direction along the axis with respect to the piston,
Of the pair of reaction force adjusting springs, the spring on the pressure chamber side is disposed in a liquid chamber formed between the piston and the input piston,
In the piston,
The fluid chamber communicates with the reservoir of the master cylinder from the non-braking position of the piston where the brake pedal is not operated to the vicinity of the assist limit position of the piston where the assist by the electric actuator is the limit. There is a communication path ,
The electric booster is characterized in that when the piston is located in a section where the brake pedal is further depressed from the assist limit position, communication with the reservoir is blocked .

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