Electromechanical brake assist system

Abstract

An electromechanical brake assist system driven by an electric motor cooperating with a master cylinder and having, along the axis of actuation, a helper piston in the shape of an axial sleeve solidly connected with a guide bracket and having a threaded surface. A nut, fixed in translation but free to rotate, has interior threads that complement those of the helper piston, which it receives, and exterior teeth that cooperate with the drive motor. A plunger piston carries a drive base so it can be pushed by the piston. Its other extremity is connected to the control rod, formed from a body and a head. The body has a crimping area and the head has a sleeve with an extremity that can be crimped along the crimping area.

Claims

1. An electromechanical brake assist system driven by an electric drive motor cooperating with a master cylinder, the brake assist system comprising: a helper piston accommodating a guide bracket that carries an axial sleeve, the guide bracket being guided in translation and fixed in rotation, the sleeve having a threaded exterior surface, which cooperates with a nut, the nut being fixed in translation but free to rotate, and having internal threads that complement threads of the sleeve, the nut having an exterior surface configured for connection to a gear that in turn is configured for connection to the electric drive motor; a plunger piston having at its front extremity a drive base that can be pushed by the helper piston and connected to a control rod at its back extremity; wherein the control rod is formed from a body one of whose extremities is connected to the plunger piston and the other extremity to a head; wherein the body of the control rod has, at its rear extremity, a crimping area; wherein the head has a crimping sleeve at its front extremity, the crimping sleeve crimped onto the crimping area of the body; and wherein the crimping area of the body is one of a knurled or grooved surface, whose orientation is transverse to a direction of an axis of actuation.

2. The brake assist system according to claim 1, wherein the front extremity of the body of the control rod extends beyond the crimping area in a smooth surface, and the crimping sleeve of the head has a crimping entryway of reduced thickness, a geometry of the crimping sleeve and the crimping entryway corresponding to the smooth extremity and to the crimping area of the body.

3. A method for providing a plunger piston-control rod assembly of an electromechanical brake assist system, comprising: providing a control rod having a body with a crimping area at an end of the control rod for accommodating a head while leaving a portion of the control rod smooth; providing the head, the head including a sleeve equipped with a crimping entryway at end of the head opposite a ball stud of the head; assembling a plunger piston with the control rod, the plunger piston being engaged with the control rod in a helper piston; placing the head on the body of the control rod; and crimping the crimping entryway along the crimping area of the body, wherein the crimping area of the body is one of a knurled or grooved surface, whose orientation is transverse to a direction of an axis of actuation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described below in greater detail by means of an example of a brake assist system with an electric motor, as shown in the figures.

(2) FIG. 1 is an exploded view of the portion of the brake assist system composed of the plunger piston, the control rod, and the helper piston, aligned along the system's xx axis.

(3) FIG. 2 is an axial cutaway of the plunger piston and the control rod, along with the assembly consisting of the stop for the cutoff spring and the head of the control rod.

(4) FIGS. 3A-3C illustrate the steps for assembling the plunger piston and the control rod with its control rod head.

(5) FIG. 4 is a perspective view of the final assembly.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) To simplify the description, the front (AV) is the left side of the xx axis of FIG. 1 and the rear (AR) is the right side.

(7) The brake assist system according to the present invention, of which only certain elements needed for the description are shown, appears in the exploded view of FIG. 1, composed of a master cylinder (for example, a tandem master cylinder) supplying one or two brake circuits with pressurized brake fluid. The master cylinder is controlled from the brake pedal by a kinematic chain encompassing an actuator in the form of an electric motor, providing, by itself or together with the thrust from the pedal, the force exerted on the primary piston of the master cylinder.

(8) Beginning with the brake pedal, the kinematic chain aligned along line of action xx consists of a rod connected to the pedal and transmitting its movement to control rod 1, which is itself connected to plunger piston 2, to receive the additional helper thrust for acting directly on the master cylinder or by the assist system.

(9) The thrust is transmitted to the tandem master cylinder by a pushrod accommodating a reaction disk against which presses an intermediary piston directly pushed by the helper piston (elements not shown), wherein the plunger piston can also be applied to this reaction disk.

(10) To do so, plunger piston 2 cooperates with helper piston 3 while being directly connected to control rod 1. Helper piston 3 accommodates guide bracket 31, guided in translation and fixed in rotation. Bracket 31 carries threaded sleeve 32, accommodating translation nut 33. It is traversed by plunger piston 2 and control rod 1. Helper piston 3 is supported on the xx axis by bracket 31, equipped with two bearings 311 to slide on two guide rods (not shown) parallel to the xx axis. Helper piston 3 is pushed in the direction of assistance (arrow A) through the cooperation of threaded sleeve 32 and the threads on translation nut 33. The latter, fixed in translation in the direction of axis xx, has interior threads so it can be screwed on threads 321 of sleeve 32 of helper piston 3. On the outside, nut 33 has grooves 331 to accommodate a gear equipped with grooves of a complementary shape, making the assembly rotationally interdependent. This gear (not shown) cooperates with a drive gear on the electric drive motor for brake assistance. Helper piston 3 rests upon drive base 21 integral with plunger piston 2 to push it while it makes contact with an intermediary piston to push, using a pushrod (elements not shown), on the master cylinder (arrow A). Drive base 21 consists of a cross-brace whose two branches 210 are equipped with guide stops 211 in the direction of axis xx. The stops slide in bearings 312 of bracket 31. One of the branches also carries lug 212 parallel to axis xx and cooperating with the trigger sensor to actuate the helper motor after the empty stroke of this type of control at the start of an assisted braking operation.

(11) Plunger piston 2 is connected to control rod 1 formed from body 11 and head 12. The front extremity of body 11 is fixed to the rear extremity, the side not turned to the master cylinder, of plunger piston 2; its rear extremity accommodates head 12 of the control rod. Head 12, formed from sleeve 121 with crimping entryway 122, terminates in the rear at ball stud 123 for connection to the rod from the brake pedal. Crimping entryway 122 is part of sleeve 121 of reduced thickness, and deformable by crimping along crimping area 111. Body 11 of the control rod has crimping area 111, formed by a knurled annular surface, for example in the form of peripheral grooves or channels. These peripheral deformations are oriented primarily in the direction transverse to the axis of actuation, which is also the axis of the actuator rod or its body, so as to provide excellent strength for crimping in the direction of tractive and compressive forces. Crimping area 111 is near the second extremity while nevertheless leaving fitting length 112. Sleeve 121 of head 12 is engaged in extremity 112, 111 of body 11 of the rod, then it is crimped.

(12) FIG. 2 is an axial cutaway illustrating body 11 with its front extremity attached to plunger piston 2 and its rear extremity crimped to sleeve 121 of head 12, this axial assembly being engaged in sleeve 32 of helper piston 3, which is itself engaged in translation nut 33.

(13) As shown in FIGS. 3A-3C, installation takes place by assembling, along axis xx, plunger piston 2 with body 11 of control rod 1, then installing the plunger piston in helper piston 3, followed by translation nut 33 and cutoff spring 4, then head 12 is installed and crimped. Sleeve 121 serves to maintain head 12 on body 11 in the direction transverse to the axis of actuation to stiffen the assembly and relieve the crimping, which enables the assembly to resist forces in the direction of axis xx, that is, compressive and tractive forces.

(14) As shown in FIG. 3A, plunger piston 2, joined with body 11 of control rod 1, is engaged in helper piston 3, with its bracket 31 and its sleeve hidden by translation nut 33.

(15) Body 11 projects beyond the end of sleeve 32 and nut 33 and leaves visible crimping area 111 and smooth extremity 112.

(16) Cutoff spring 4 is presented on axis xx so it can be fitted on body 11 and come to rest against the extremity of sleeve 32 of helper piston 3, the other extremity of the cutoff spring resting against a lock washer engaged on control rod 1.

(17) FIG. 3B illustrates a subsequent step that includes the installation of elastic sleeve 5, covering body 11 and spring 4, while leaving crimping area 111 and smooth extremity 112 free to accommodate sleeve 121 with its crimping entryway 122.

(18) Sleeve 121 maintains head 12 on smooth part 112 along axis xx, and crimping entryway 122 of reduced thickness allows for the deformation of crimping along crimping area 111.

(19) FIG. 3C illustrates the final disposition of head 12 after crimping, leaving visible the crimping deformations along crimping entryway 122.

(20) FIG. 4 is a perspective view illustrating the completed installation, showing housing 6 of the helper module and head 12 of the control rod extending beyond sleeve-bellows 5. Sleeve-bellows 5 protects the part of the control rod beyond the translation nut with the cutoff spring.

(21) The transmission of motor 7, partly represented, is hidden by housing 6.

REFERENCE KEY

(22) 1 Control rod 11 Body of the control rod 111 Crimping area 112 Smooth extremity

(23) 12 Head of the control rod 121 Sleeve 122 Crimping entryway 123 Ball stud

(24) 2 Plunger piston 21 Drive base 210 Branch 211 Guide stop 212 Lug for trigger sensor

(25) 3 Helper piston 31 Bracket 311 Slide bearing 312 Slide opening 32 Threaded sleeve 321 External threads 33 Nut 331 Groove

(26) 4 Cutoff spring

(27) 5 Sleeve-Bellows

(28) 6 Module housing

(29) 7 Electric motor