Parking brake for an automatic transmission mechanism

A parking brake for the automatic transmission mechanism of a vehicle so constructed as to affect no adverse influence on the operation of the automatic transmission mechanism even though a change lever is positioned in a parking range while the vehicle is running. The parking brake includes a first roller fixedly disposed to cooperatively rotate with an output shaft; a second roller coaxially movable with the first roller but disposed not to rotate; a restricting unit disposed at a facing surface between the first roller and the second roller to restrict the rotation of the first roller when the first and second rollers are in close adherence; and a driving unit for slidingly moving the second roller according to the selection or non-selection of the change lever to the parking position to couple and detach the first and second rollers.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a parking brake and more particularly to a
 parking brake for an automatic transmission mechanism.
 2. Description of the Prior Art
 Generally, a vehicle mounted with an automatic transmission mechanism is
 established with a transmission range covering parking (P), reverse
 driving (R), neutral (N), driving (D) and the like.
 When a change lever at the transmission range is positioned at a parking
 range, an output axle is mechanically restricted to allow a vehicle to
 maintain a parking state, but in order to maintain the parking state a
 separate parking mechanism is needed.
 As illustrated in FIGS. 4 and 5, the separate parking mechanism includes a
 change lever assembly 51 where a change lever 50 is so disposed as to be
 movable to each range, a manual lever 54 protrusively disposed at a
 transmission case 52 and internally connected by a detent plate 53, a
 control cable 55 connecting the change lever assembly 51 and the manual
 lever 54, a parking rod 56 connected at one end thereof to the detent
 plate 53 for slideable movement, a parking lever 58 connected at one end
 thereof to the parking rod 56 for rotation by way of a hinge shaft 57 and
 a parking gear 60 intermittently restricted by the parking lever 58 and so
 mounted as to be cooperatively connected to an output shaft 59.
 Furthermore, the parking lever 58 is provided with a spring 61 which is
 supported at one end thereof by a fixed portion and is connected thereto
 at the other end thereof, such that the parking lever 58 is always
 detached from the parking gear 60 to apply resilience thereto.
 In other words, the parking lever 58 is rotatably moved to intermittently
 restrict the parking gear 60, and when the parking gear 60 is restrained,
 the output shaft 59 is put to a restricted state to allow a vehicle to
 maintain the parking.
 Now, operation of the parking brake mechanism thus described will be
 explained.
 When a driver shifts the changer lever 50 to a parking (P) position to park
 a vehicle, the control cable 55 rotates the manual lever 54 and
 simultaneously rotates the detent plate 53 connected thereto. When the
 detent plate 53 is rotated, the parking rod eccentrically connected
 thereto is moved to the right direction on the FIG. 4.
 When the parking rod 56 is moved to the right side, the parking lever 58
 adhered to a tip end of the parking rod 56 is rotated clockwise about the
 hinge shaft 57, where a tip end of the parking lever 58 is inserted into
 gear grooves of the parking gear 60. When the parking lever 58 is inserted
 into the gear grooves of the parking gear 60 to thereby prevent the
 parking gear 60 from rotating, the output shaft 59 where the parking gear
 60 is fixedly disposed is refrained from rotating, thereby causing the
 vehicle to maintain the parking state.
 SUMMARY OF THE INVENTION
 However, there is a problem in that, when the control cable activates the
 parking rod and the parking lever according to movement of the change
 lever as described above, heavy impact is generated on the parking lever
 and the parking gear when the change lever is shifted to the parking range
 by a driver during change lever manipulation while the vehicle is running,
 and still worse, the automatic transmission mechanism can be damaged to
 make the vehicle inoperable.
 Furthermore, an operating direction of the parking lever is on a straight
 line relative to a rotating direction of the parking gear, such that, when
 the parking gear is rotated by a relatively strong force such as sudden
 start (due to erroneous operation of the automatic transmission mechanism)
 and the like, the parking lever resiliently supported by a spring is
 detached from the gear grooves of the parking gear to thereby cause an
 accident to occur.
 The present invention is disclosed to solve the aforementioned problem and
 it is an object of the present invention to provide a parking brake for
 automatic transmission mechanism configured not to affect the operation of
 the automatic transmission mechanism even though the change lever is
 positioned at a parking range while the vehicle is running, thereby
 preventing noise and damage.
 Furthermore, the output shaft is firmly secured even when a vehicle mounted
 with an automatic transmission mechanism is started suddenly, such that a
 braking force is increased while the vehicle is parked to thereby maintain
 a parking state of the vehicle.
 In accordance with the object of the present invention, there is provided a
 parking brake for automatic transmission mechanism, the brake adapted to
 restrict an output shaft according to a change lever at the automatic
 transmission mechanism being selectively positioned at a parking range to
 thereby generate a braking force while a vehicle is parked, wherein the
 brake comprises:
 a first roller fixedly disposed to cooperatively rotate with the output
 shaft;
 a second roller coaxially movable with the first roller but disposed not to
 rotate;
 restricting means disposed at a facing surface between the first roller and
 the second roller to restrict the rotation of the first roller when the
 first and second rollers are closely adhered; and
 diving means for slidingly moving the second roller according to selection
 and non-selection of the change lever to the parking position to couple
 and detach the first and second rollers.

DETAILED DESCRIPTION OF THE INVENTION
 Embodiments of the present invention will now be described in detail with
 reference to the accompanying drawings.
 FIGS. 1 and 2 are respectively a schematic diagram for illustrating a
 parking brake for automatic transmission mechanism according to the
 present invention and a schematic sectional view of principal parts
 thereof, where the brake includes:
 a first roller 1 fixedly disposed to cooperatively rotate with an output
 shaft 59;
 a second roller 2 so formed as to allow the first roller 1 to be inserted
 thereinto for being coaxially movable with the first roller 1 but disposed
 not to rotate;
 restricting means disposed at a facing surface between the first roller 1
 and the second roller 2 to restrict the rotation of the first roller 1
 when the first and second rollers 1 and 2 are closely adhered; and
 driving means for slidingly moving the second roller according to selection
 and non-selection of a change lever to the parking position to couple and
 detach the first and second rollers 1 and 2.
 The restricting means defines splines 3 each oppositely formed between the
 first and the second rollers 1 and 2, thereby restricting the rotation by
 being mutually inserted therebetween. Of course, the same restricting
 effect can be obtained if a construction is so made as to employ a spur
 gear and the like for being meshed to restrict the rotation, without using
 the splines 3.
 Particularly, contact surface between the first and the second rollers 1
 and 2 is disposed with synchroneous means for decreasing a rotating speed
 of the first roller 1 by way of friction before two rollers 1 and 2 are
 mutually contacted when the first roller 1 rotates with the output shaft
 59 at a high speed and for contacting the first and second rollers 1 and 2
 after the reduced rotating speed.
 The synchroneous means includes a first taper 4 formed at an outer
 periphery of the first roller 1 and a second taper 5 formed in
 groove-shape at an inner surface of the second roller 2 for gradually
 contacting the first taper 4 to get increased friction force and for
 maximizing the friction force just before coupling of the splines 3 to
 thereby stop the first roller 1.
 The driving means includes a bracket 7 fixed to the transmission mechanism
 case 52 and coupled to the second roller with splines 6 for enabling the
 second roller 2 to horizontally slide along for restriction of rotation, a
 pressure plate 9 disposed at a bottom surface of the second roller 2 for
 functioning as an actuator 8, and electronic control unit ECU 11 connected
 to a sensor 10 for actuating the actuator 8 and for sensing a parking
 range selection of the change lever 50 and a spring 12 so disposed as to
 pull second roller 2 toward the pressure plate 9.
 Between the second roller 2 and the pressure plate 9 there is disposed a
 wavy disc-shaped spring 13 to cushion an impact generated when the first
 and the second roller 1 and 2 are closely adhered.
 At this location, another embodiment of the driving means is shown in FIG.
 3, where the driving means is disposed with the pressure plate 9 connected
 by a hydraulic cylinder 8' controlled by the ECU 11, the hydraulic
 cylinder 8' is mounted with a hydraulic pump 14 for supplying and blocking
 the hydraulic oil to the hydraulic cylinder 8' and a storage tank 15 for
 supplying the oil is connected to the hydraulic pump 14.
 In other words, construction thereof is so arranged as to make a hydraulic
 apparatus (hydraulic cylinder, hydraulic pump and the like) having a
 relatively strong actuating power move the second roller 2, such that
 adherence of the first and second rollers 1 and 2 is further strengthened
 to thereby enable a parking state to be maintained even during the
 occurrence of the sudden start.
 Now, operational effect of the present invention will be described. If a
 driver mistakenly positions the change lever 50 at a parking range while a
 vehicle is running, the sensor 10 detects that the change lever 50 is
 selected to be positioned at the parking range and transmits same to the
 ECU 11.
 When a parking signal is transmitted to the ECU 11, the ECU 11 actuates the
 actuator 8 to move the pressure plate 9 towards the first roller 1, and
 when the second roller 2 is moved over the splines 6 by the pressure plate
 9, the first and second tapers 4 and 5 formed at the contact surface of
 the first and second rollers 1 and 2 gradually get in touch. When the
 first and second tapers 4 and 5 gradually become in contact, the first
 roller 1 is gradually reduced in rotating speed thereof and the contact
 surface of the first and second rollers 1 and 2 gets increased to
 virtually stop the speed of the first roller 1.
 When the rotating speed of the first roller 1 is almost stopped, the
 splines 3 oppositely formed relative to the first and second rollers 1 and
 2 are coupled to restrict the first roller 1. At this time, the wavy
 spring 13 provided between the second roller 2 and the pressure plate 9
 serves to cushion the amount of impact when the first and the second
 roller 1 and 2 are contacted therebetween.
 In other words, the reversing force of the second roller 2 generated by the
 impact when the first and second rollers 1 and 2 touch presses the wavy
 spring 13 which in turn cushions the amount of the impact.
 When the splines 3 formed between the first and the second roller 1 and 2
 are coupled to thereby restrict the output shaft 59 and to prevent a
 vehicle from driving, where, because the splines 3 coupling the first and
 second rollers 1 and 2 are coupled on a parallel line with a rotary
 centerline of the output shaft 59, the force for restricting the first
 roller 1 is markedly strengthened as compared with the restricting force
 coming from the tangential direction in the prior art.
 In other words, in the prior art, the rotary direction of the parking gear
 60 and that of the parking lever 58 direct the same direction on the same
 planer, such that the parking lever 58 is easily rotated about the hinge
 shaft 57 by the turning force of the parking gear 60 to easily release the
 parking restriction but the present invention restricts the first roller 1
 in the parallel direction (normal direction) relative to the rotary
 direction to thereby increase the braking force remarkably.
 Particularly, because the first roller 1 limits the second roller from the
 normal direction, increased braking force while a vehicle is parked
 according to coupling of the first and second rollers 1 and 2 and the
 hydraulic system strongly adhere the first and the second roller 1 and 2
 together to thereby prevent the sudden start of the vehicle which occurs
 due to erroneous operation of the automatic transmission mechanism.
 Of course, when the change lever 50 is selected to be positioned at the
 parking range when a vehicle is being parked and stopped, the synchroneous
 state is not realized by the first and second taper 4 and 5 and the
 splines 3 are coupled to thereby park the vehicle.
 As apparent from the foregoing, there is an advantage in the parking brake
 for the automatic transmission mechanism according to the present
 invention in that a parking brake mechanism is so provided as to restrict
 a first roller disposed at an output shaft in a vehicle mounted with an
 automatic transmission mechanism to the normal direction relative to a
 rotating direction, thereby increasing a parking brake force of the
 vehicle and preventing a sudden start when the automatic transmission
 mechanism is erroneously operated.
 Furthermore, there is another advantage in that even though the change
 lever is selected to be positioned in the parking range during the running
 of a vehicle, the first and second tapers realize a synchronization to
 adhere the first and second roller, preventing generation of noise and
 damage of the automatic transmission mechanism.