Electric braking apparatus
One of brake pads 5 is pressed against the disc rotor D by a piston of a caliper 3 which is floatably supported on the carrier 2, and in reaction thereto, the other brake pad 5 is pressed against the disc rotor D by a claw portion 14 on the caliper 3, thereby producing a braking force. During brake release, the spring force of a return spring 22 separates the brake pad 5 from the disc rotor D. A positioning convex portion 27 is provided on the carrier 2 in a standing position adjacent to the return spring 22, and serves to restrict the sideward movement of the distal end portion of the return spring 22. Thus displacement and deformation of the return spring can be prevented, and its functions can be maintained.
This application is a divisional application of Ser. No. 10/209,836 filed Jul. 30, 2002, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTIONThe present invention relates to an electric braking apparatus for producing braking force by torque of a motor, and particularly to an electric braking apparatus added with a parking brake function.
There are currently electric braking apparatuses with a caliper comprising a piston, a motor and a rotation-linear movement conversion mechanism for converting rotation of the motor into linear movement. In such an electric braking apparatus, the piston is moved in accordance with rotation of a rotor of the motor to thereby press a brake pad against a disk rotor and produce braking force. Further, such an electric braking apparatus normally has a sensor for detecting pressing force or a stroke distance of a brake pedal depressed by an operator and controls the amount of the rotation (a rotational angle) of the electric motor in accordance with the detection results detected by the above sensor to thereby achieve the desired braking force.
However, in recent times, there have been various attempts made to enhance the functionality of an electric braking apparatus of this kind by adding the parking brake function. For example, U.S. Pat. No. 5,348,123 and corresponding German Patent Laid-open No. (Offenlegungsschrift) DE4229042A1 have proposed a mechanical brake operating mechanism in which a rotating shaft is connected to a pivoting member of the rotation-linear movement conversion mechanism described above via a clutch mechanism and a ball ramp mechanism. A rotational force is exerted on the rotational shaft from the outside by an operation of, for example, a lever, to engage the clutch via the ball ramp mechanism, thereby placing the rotation-linear movement conversion mechanism in operation to produce braking force.
However, in the mechanical brake operating mechanism described in the above publications, when the brake pedal is depressed while the parking brake is made effective by the operation from the outside, the problem arises that since the rotation-linear movement conversion mechanism is operationally connected to the outside operating portion via the clutch mechanism, the electric brake does not operate. Further, it is also a problem that since the rotating shaft is connected in series to the pivoting member of the rotation-linear movement conversion mechanism via the clutch mechanism and the ball ramp mechanism, the caliper is elongated in the axial direction. Therefore, the mechanical brake operating mechanism may not be suited for all vehicles due to possible interference with the wheel.
The invention has been made in view of the above-described technical background. It is a purpose thereof to provide an electric braking apparatus equipped with a parking brake function that does not interfere with the normal braking operation of the braking apparatus. It is still another purpose thereof to provide an electric braking apparatus that can be mounted on any vehicles.
SUMMARY OF THE INVENTIONIn order to resolve the above-described problem, according to an aspect of the invention, there is provided an electric braking apparatus with a caliper comprising a piston, a motor and a rotation-linear movement conversion mechanism for converting rotation of the motor into linear movement and transmitting the linear movement to the piston, so that the piston is moved in accordance with the rotation of a rotor of the motor to press a brake pad against a disk rotor to generate braking force, wherein a parking brake locking mechanism is arranged around the rotor, which functions to restrict rotation of the rotor in the brake releasing direction when no electricity is supplied to the motor and to release the restriction on the rotor in accordance with the amount of electricity supplied to the motor.
In the electric braking apparatus according to such constitution, when electricity supplied to the motor is cut after braking force caused by rotation of the rotor of the motor has been generated, the parking brake locking mechanism operates to restrict rotation of the rotor, the braking force is maintained and the parking brake thus carries out its function. Under this condition, when a supply of electricity to the motor begins, the rotor begins to rotate, so that the parking brake locking mechanism unlocks and the parking brake is automatically released. Further, the parking brake locking mechanism is arranged around the rotor and therefore, the length of the caliper in the axial direction is not enlarged.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed explanation will be given of embodiments of the invention in reference to the attached drawings.
According to the embodiment, inside the caliper 2, there are arranged a piston 11 capable of abutting against the back face of the brake pad 3 facing the interior of the vehicle; a motor 12; a ball ramp mechanism (a rotation-linear movement conversion mechanism) 13 for converting rotational movement outputted from the motor 12 into linear movement and transmitting the linear movement to the piston 11; a differential speed reducing mechanism 14 for reducing the rotation speed of the motor 12 and transmitting the rotation to the ball ramp mechanism 13; a pad wear compensating mechanism 15 (
As shown by
The motor 12 is provided with a stator 25 fixedly fitted in the motor case 9. A hollow rotor 26 is arranged inside the stator 25. The rotor 26 is pivotally supported by the motor case 9 and the support plate 8 through bearings 27 and 28. With the instruction from a controller (not illustrated), the motor 12 is operated to rotate the rotor 26 with desired torque and over desired angle. The rotational angle of the rotor 26 is detected by a rotation detector, not illustrated, arranged inside the rotor 26. Further, the caliper main body 10 is attached with a connector 29 for dealing with a signal line that connects the stator 25 and the rotation detector and the controller.
The ball ramp mechanism 13 is provided with a ring-shaped first disk (a pivoting member) 31 pivotally supported by the inner periphery of the annular base member 6 of the caliper main body 10 via a cross roller bearing 30, a ring-shaped second disk (a linearly moving member) 32 coupled to the shaft portion 21 of the piston 11 via screw portion S, and three balls 33 interposed between the two disks 31 and 32. The second disk 32 is arranged to abut against the rear face of the main body portion 20 of the piston 11 and is normally restricted from rotating by friction force of a wave washer 34 interposed between the second disk 32 and the caliper main body 10.
The three balls 33 are respectively disposed between three ball grooves 35 and 36 respectively formed on respective faces of the first disk 31 and the second disk 32 facing each other along the circumference. The three ball grooves 35 and 36 are inclined in the same direction and arranged to shift axially by the same interval in the range of the same center angle (for example, 90 degrees). When the first disk 31 is rotated in the counterclockwise direction as viewed from the right in
Meanwhile, on the portion of the second disk 32 screwed to the shaft portion 21 of the piston 11 (screw portion S) is continuously provided with the extended cylindrical portion 37 greatly extended toward the end plate 22 of the motor case 9. Inside of the extended cylindrical portion 37 there is arranged disk springs 38 one of which is fixed to the support rod 23 and which normally urge the second disk 32 toward the first disk 31 via the extended cylindrical portion 37. Thereby, the balls 33 of the ball ramp mechanism 13 are strongly pressed between the two disks 31 and 32, and when the first disk 31 is rotated clockwise as viewed from the right in
As is well shown in
The rotation ratio N of the first disk 31 to the rotor 26, becomes N=(D−d)/D, where d is the diameter of a reference circle of a cycloid groove on the side of eccentric plate 41 in the cycloid ball speed reducing mechanism 43 and D is the diameter of a reference circle of a cycloid groove on the side of the first disk 31. In this case, the number of rotations of the rotor 26 when the first disk 31 is rotated by one rotation is the speed reduction ratio α (=1/N). Further, the second disk 32 is moved forward by S=(L/360)×(θ/α) where the rotor 26 is rotated by a certain angle θ; the rotational angle θA of the first disk 31 is θ/α; and L is the inclination (lead) of the ball grooves 35 and 36 of the ball ramp mechanism 13.
As is well shown in
The pad wear compensating mechanism 15 functions in such a manner that, when the brake pads 3 and 4 are worn, the limiter 44 rotates in accordance with rotation of the first disk 31 of the ball ramp mechanism 13, and that that rotation is then transmitted to the second disk 32 via the coil spring 47, the spring holder 46 and the pin 45, and that the piston 11, restricted in rotation by the support pin 23, moves forward along the support pin 23 until the brake pad 3 is pressed to the disk rotor D, i.e., until the braking force is generated, so that the gap caused by the pad wear is eliminated. Meanwhile, after producing the braking force, the large friction resistance produced at the screw portion S between the piston 11 and the second disk 32 hampers rotation of the second disk 32. Therefore, rotational misalignment between the second disk 32 and the first disk 31, that is, rotational misalignment between the spring holder 46 and the limiter 44 is absorbed by twisting of the coil spring 47.
As is well shown by
Each of the tooth portions 57 of the claw wheel 50 is given a tooth shape in which a steep tooth engaging face 57a faces in direction L that the rotor 26 rotates when braking is being released (the counterclockwise direction when viewed from the right in
An explanation will be given of operation of the electric braking apparatus according to the first embodiment also in reference to
(In Operating Electric Brake)
When the apparatus is operated as a normal electric brake, the rotor 26 of the motor 12 rotates in the clockwise direction as viewed from the right in
Further, when the electric brake is operated, the claw wheel 50 of the parking brake locking mechanism 16 rotates in the clockwise direction R, along with the rotor 26. As a result, the engaging claw 54 slides along the inclined escape face 57b of a tooth portion 57 while abutting against the projection 59. Since the rotational torque of the rotor 26 is sufficiently larger than the urging force of the tensile spring 55, the arm lever 52, as shown in
(In Releasing Electric Brake)
When the river releases the operation of electric brake, the rotor 26 of the motor 12 rotates counterclockwise as viewed from the right in
At the same time, the claw wheel 50 of the parking brake locking mechanism 16 rotates in the counterclockwise direction L integrally, along with the rotor 26, so that as shown in
(In Operating Parking Brake)
When the driver activate the parking brake, the rotor 26 of the motor 12 rotates in the clockwise direction R. The piston 11 then moves to produce the braking force as is the above case where the electric brake is turned on. Further, according to the first embodiment, control is made on supply of electricity to the motor 12 to cut it off simultaneously with the production of the braking force. When electricity is cut off, a rotational torque appears in the counterclockwise direction L on the rotor 26 of the motor 12 by influence of rigidity of the caliper or the like. This rotational torque exerts downward force on the engaging claw 54 of the parking brake locking mechanism 16 is pushed down. However, since the rotational torque from the rotor 26 is significantly smaller than that from it when the electric motor is operated, the engaging claw 54 is held, due to the urging force of the torsion spring 58, in the projecting position shown in
(In Releasing Parking Brake)
When the driver releases the parking brake, electricity begins to flow through the motor 12. As is the case where the electric brake is turned off, the rotor 26 rotates in the counterclockwise direction (brake releasing direction) L, and the claw wheel 50 of the parking brake locking mechanism 16 also rotates in the same direction L integrally, along with the rotor 26. Since the rotational torque of the rotor 26 at this time is considerably larger than the urging force of the torsion spring 58 trying to hold the engaging claw 54 in the projecting position, as shown in
An explanation will be given of operation of the electric braking apparatus according to the second embodiment.
(Actuating the Electric Brake)
In the normal operation of the electric braking apparatus, the rotor 26 of the motor 12 rotates clockwise as seen from the right in
(Deactivating the Electric Brake)
When the driver releases the electric brake, the rotor 26 of the motor 12 rotates counterclockwise as viewed from the right in
(Activating the Parking Brake)
When the driver operates the parking brake, the rotor 26 of the motor 12 rotates in the clockwise direction R. Similarly to the normal operation of the electric brake, the piston 11 moves to generate the braking force. Further, according to the second embodiment, control is made on the electricity supplied to the solenoid 62 of the parking brake locking mechanism 16 and the motor 12 so as to cut it off simultaneously with generation of the braking force. As supply of electricity to the solenoid 62 is cut off, as shown in
(Releasing the Parking Brake)
When the driver releases the parking brake, electricity begins to flow though the solenoid 62 of the parking brake locking mechanism 16 to extend the plunger 61 of the solenoid 62. The engaging claw 54 of the brake locking mechanism 16 is held slightly away from the tooth portion 57 of the claw wheel 50 as shown in
Further, according to the second embodiment, if the solenoid 62 becomes inoperative, as shown in
An explanation will be given of operation of the electric braking apparatus according to the third embodiment.
(Activating the Electric Brake)
When the apparatus performs the normal braking operation, with a brake operating signal from the driver, the rotor 26 of the motor 12 rotates clockwise as viewed from the right in
(Releasing the Electric Brake)
When the driver release the electric brake, the rotor 26 of the motor 12 rotates counterclockwise as viewed from the right in
(Activating the Parking Brake)
When the driver operates the parking brake, the rotor 26 of the motor 12 rotates in the clockwise direction R. The piston 11 thereby moves as it does in the normal operation of the electric brake to generate the braking force. Further, according to the third embodiment, control is made in such manner that electricity begins flowing through the solenoid 72 of the brake locking mechanism 16 simultaneously with generation of the braking force while electricity to the motor 12 is cut off. With supply of electricity to the solenoid 62, the plunger 73 extends. The engaging claw 54′ is thereby positioned so that it engages with the claw wheel 50 against the urging force of the tensile spring 71, as shown in
(Releasing the Parking Brake)
When the driver releases the parking brake, supply of electricity begins to the motor 12. The rotor 26 then rotates slightly in the clockwise direction (braking direction) R. By the urging force of the tensile spring 71, the engaging claw 54′ rotates counterclockwise away from the tooth portion 57 of the claw wheel 50. When the rotor 26 of the motor 12 is thereafter rotated in the counterclockwise direction (brake releasing direction) L thereafter at an appropriate timing, the claw wheel 50 of the parking brake locking mechanism 16 smoothly rotates in the counterclockwise direction L, along with the rotor 26, without contacting the engaging claws 54 (
According to the third embodiment, when the parking brake is operated, electricity is supplied only temporarily to the solenoid 72. Thus, heat generation from the solenoid 72 is suppressed.
As is well shown in
The locking mechanism 150 is provided with: a claw wheel 152 integrally formed around the outer peripheral of the rotor 26; an arm lever 154, arranged near the claw wheel 152, the base end portion of which is pivotally attached to the caliper main body 10 by using a pin 153; an engaging claw 156, the base end portion of which is pivotally attached to the mid portion of the arm lever 154 by using a pin 155; a stopper portion 157 provided at the caliper main body 10 against which the arm lever 154 abuts along its side and is held thereby in the direction tangential to the rotor 26; a torsion spring (urging means) 158 for normally urging the engaging claw 156 counterclockwise as viewed in
The solenoid 151, serving as an actuator, is of a two direction self-holding type. As shown in
As shown by
In the parking brake locking mechanism 116 of such a structure, when electricity is supplied to the coil 164 of the solenoid 151, the rod 166, being supported by the plunger 161, moves left A (the forward moving direction) in
Operation of the electric braking apparatus according to the fourth embodiment will here be explained, referring again to
(Normal Braking Operation)
When the drive initiates the normal braking of the electric brake, the rotor 26 of the motor 12 rotates clockwise as viewed from the right in
(Releasing the Normal Braking)
When the driver releases the electric brake, the rotor 26 of the motor 12 rotates counterclockwise as viewed from the right in
(Occurrence of Failure During the Normal Braking Operation)
If a failure occurs in the electric circuit of the motor 12 for some reason during the above-described normal braking operation, the torque (current) of the motor 12 drops as shown in
(Operation of the Parking Brake (PKB))
When the driver operates the parking brake, the rotor 26 of the motor 12 rotates clockwise as viewed from the right in
(Releasing the Parking Brake (PKB))
When the driver releases the parking brake, electricity is supplied temporarily to the coil 164 (
(Occurrence of Failure During the Parking Brake Operation)
Suppose that the solenoid 151 fails or becomes inoperable for some reason while the parking brake is in operation. When the driver releases the parking brake, electricity is supplied to the motor 12 as happens when the electric brake is released. The rotor 26 then rotates counterclockwise as viewed from the right in
As has been described in detail, according to the electric braking apparatus of the invention, the parking brake is operated by utilizing rotation of the motor. Therefore, the parking brake function can sufficiently be achieved without sacrificing the basic braking function of the apparatus as an electric brake. Thus, the reliability of the apparatus is significantly improved.
Further, the parking brake locking mechanism is arranged around the rotor. Therefore, the axial length of the caliper can be made short, whereby the mountability of the apparatus to the vehicle is improved. Particularly, when the parking brake locking mechanism is arranged inside the caliper, the mountability to the vehicle is further improved.
Further, if the parking brake locking mechanism functions in such a manner that it releases the lock by operation of the rotational torque generated when electricity is supplied to the motor, since the parking brake locking mechanism can be unlocked by merely rotating the rotor in the brake releasing direction, control of the motor is simplified.
Further, if the parking brake locking mechanism functions in such a manner that an actuator having self-holding capability locks and unlocks the locking mechanism, the parking brake function can be sufficiently achieved without sacrificing the basic electric brake function. Further, even if the motor fails, the parking brake can be released with certainty. Thus, the reliability of the apparatus is significantly improved.
Further, when the self-holding type solenoid is used as the actuator, the structure of the actuator becomes simple and compact. Therefore, the caliper can be made small. Further, since electricity does not have to be constantly supplied, the apparatus contributes to power saving.
Further, when there is provided a piston returning mechanism for returning the piston to the reference position when there is no current supplied to the motor, even in case of failure in the motor and the actuator, by the function of the piston returning mechanism, the parking brake can reliably be released.
Claims
1-16. (canceled)
17. An electric braking apparatus comprising:
- an electric motor that is controlled in such a manner that it is activated to effectuate a parking brake and deactivated when the parking brake becomes in effect;
- a mechanism that converts rotation of the motor into linear braking action of friction members to effectuate and release the parking brake and transfers brake reaction force back from the friction members while the parking brake is in effect;
- a first engagement element that is operably connected to the motor to move in a brake applying direction and a brake releasing direction, wherein the first engagement element is urged, while the parking brake is in effect, in the brake releasing direction by the brake reaction force transferred back from the friction members;
- a second engagement element that is brought, when the parking brake becomes in effect, into engagement with the first engagement element to hold the parking brake in effect, wherein the second engagement element is held in engagement with the first engagement element by the brake reaction force urging the first engagement element in the brake releasing direction, thereby holding the parking brake in effect while the motor is deactivated; and
- an actuator that is activated momentarily to bring the second engagement element into engagement with the first engagement element.
18. An electric braking apparatus according to claim 17, wherein when releasing the parking brake, the motor is activated to briefly move the first engagement element in the brake applying direction to release engagement between the first and second engagement elements and then move the first engagement element in the brake releasing direction.
19. An electric braking apparatus according to claim 17, wherein the second engagement element is continuously urged away from engagement with the first engagement element.
20. An electric braking apparatus according to claim 19, wherein the second engagement element comprises a spring to continuously urge itself away from engagement with the first engagement element.
21. An electric braking apparatus according to claim 19, wherein a force which results from the brake reaction force to hold engagement between the first and second engagement elements is larger than a force that urges the second engagement element away from engagement with the first engagement element.
22. An electric braking apparatus according to claim 19, wherein when releasing the parking brake, the motor is activated to briefly move the first engagement element in the brake applying direction to release engagement between the first and second engagement elements and then move the first engagement element in the brake releasing direction.
23. An electric braking apparatus according to claim 17, wherein the first engagement element comprises teeth arranged thereon, and the second engagement element comprises a claw which engages with a tooth of the first engagement element.
24. An electric braking apparatus according to claim 23, wherein each tooth has an engaging face adapted to capture the claw of the second engagement element and an escape face adapted for the claw to climb over.
25. An electric braking apparatus according to claim 23, wherein the second engagement element comprises a lever having the claw at one end, having the other end acted upon by the actuator and having a fulcrum between the ends.
26. An electric braking apparatus according to claim 17, wherein the actuator comprises a solenoid and a plunger that, when the solenoid is energized, brings the second engagement element into engagement with the first engagement element.
Type: Application
Filed: Mar 1, 2005
Publication Date: Jul 7, 2005
Inventors: Jun Watanabe (Tokyo-to), Takuya Usui (Yokohama-shi)
Application Number: 11/070,101