PARKING BRAKE

Abstract: The present invention relates to a parking brake including a lever (3) coupled to a brake wire (9) included in the brake system. Characteristic of the invention is that the lever (3) is arranged to work in two steps to achieve the desired braking power. In the first step the lever is arranged to make a translational movement for taking up wire slack in the brake system, while in the second step the lever is arranged to execute a rotation whereby the force transmission to the wire (9) takes place at a higher ratio than in the first step.

Description: PARKING BRAKE The present invention relates to an arrangement for use in connection with a parking brake for a vehicle, said arrangement including a lever coupled to at least one force transmitting wire in the brake system. Conventional parking brakes of the above type require relatively long levers to achieve the necessary torque to tension the wire. This is because these conventional systems do not have the possibility to optimally take up slack in the wire which is always present to a greater or lesser degree in the wire systems. The slack in the wire must be taken up before it is possible to utilise a greater force ratio. On taking up wire in conventional systems, the wire is wound onto a quadrant, whereby the attachment point follows the rotation of the lever and the wire is wound onto the quadrant. The shape of the quadrant contributes to a great extent to the force ratio in the system. It is quite possible to shape it such that an optimal force ratio from a force point of view can be used, but this would imply that the system would be very sensitive to slack in the wire and yielding in the system. The problem with today's systems is that, to ensure that the system does not stop working when the degree of slack increases, a more advantageous force ratio for the path (of the wire) must be used, which implies that the required application force will be high. This, in turn, contributes to the size of the lever. For conventional parking brake systems it is therefore sometimes necessary to adjust the slack in the wire. The presence of wire slack which has to be taken up by the rotation of the lever thus means that a certain adjusted angular position of the lever does not always correspond to the same wire force. Because relatively large levers are required for conventional parking brake systems the brake lever dominates the driver's area. The size also means that it is difficult to place the lever in an ergonomically advantageous position in the car. The object of the invention is to provide a parking brake in which the above mentioned problems are eliminated. This is achieved according to the invention by arranging the lever to be pulled up in two steps for achieving the desired braking power. In the first step the lever is made to perform a translational motion to take up the wire slack in the brake system. In the second step the lever is made to perform a rotational motion whereby transmission of the force to the wire is achieved with a higher force ratio than in the first step. This way of designing the parking brake has the following advantages: • Lower pulling force on the lever compared to previously known brake systems. • The lever can be made smaller. • The lever is not so dominant in the driver's area. • The lever is more easily placed in a good position in the car compared to previously known larger levers. • The slack is taken up by a translational motion, thus diminishing the need of later adjustment. • Less sensitive to wear. According to one appropriate embodiment, the invention is characterised in that a force sensing mechanism is coupled to the wire, in that the said mechanism includes a pawl arranged to retract from its locking position to allow said rotation only after the slack in the wire has been taken up and the force in the wire exceeds a chosen value. The advantage of this is that the force sensor makes it possible to control the force at which the transition between rotation and translation takes place and that the necessary pulling force on the lever during the rotational motion is always the same at the same angular position of the lever, i.e. a given position of the lever always gives the same brake power because all slack has been taken up by the translational motion. The invention will be described in the following in greater detail with reference to the attached drawings of which Fig. 1 shows a first embodiment of a parking brake according to the invention. Figs. 2-6 show in greater detail a number of parts included in the embodiment according to Fig. 1. Fig. 7 shows details of another embodiment of a parking brake according to the invention. Figs. 8-10 show further details of the embodiment according to Fig. 7. In Fig. 1 , a housing is denoted by reference numeral 1. It is intended to be embedded in the middle console of a passenger car. The two opposing sides of the housing holder have guide slots 2 in which the rotation axle 4 of the lever is placed. A housing 5 with arms 6 is attached to the same axle 4. They lie on the blocking surfaces 7 of the housing holder in the unloaded position of the parking brake shown in Fig. 1. The rotation axle 4 of the lever 3 is bevelled on its two ends and irrotationally inserted into the guide slots 2 in the two sides of the housing holder 1. A wire has been designated 9. It is attached to a brake unit (not shown) that is intended to affect the back wheels of the vehicle in the shown embodiment. The wire 9 passes over a pulley 10 before being attached to the housing 5. In Fig. 2 the housing holder 1 , the lever 3 and part of the housing have been removed compared to Fig. 1. A translation lock 1 1 is included in the parking brake. The lock is intended to cooperate with a gear (not shown) in the bottom of the housing holder. Further, there is a ratchet 12 in the form of a geared arc cooperating with the pawl 13. In the lever there is a link mechanism that locks the translation and rotation locks when the parking brake is set. By pressing the release button 14 against a spring (not shown) in the handle 15, a link mechanism for releasing the rotation lock is activated. A guide axle 16 in the link system is mounted in a guide slot 17 in the lever 3 in which a rotation axle is also present. On pressing the release button 14, the pawl 13 is always immediately withdrawn from the ratchet 12. As is apparent from Fig. 2, the release button 14 is designed in a single piece with a push component 41 inside the handle working against the said spring. The push component is equipped with a wedge shaped groove 42 which co-operates with a hemispherical end part 43 of a pressure bar 44 included in the link mechanism. The bar has a ring shaped groove 45 in which is placed a ring (not shown) that functions as a spring stop. In the lever there is a fixed spring stop (not shown) at the opposite end of the pressure bar relative to the said hemispherical end. Between the said spring stops on the pressure bar there is a pressure bar spring (not shown). On pressing the button and consequent displacement of the push component 41 , its wedge shaped groove 42 co-operates with the spherical end of the pressure bar, whereby the pressure bar is pressed against the spring. The guide axle 16 is thus displaced in the groove 17 making the lever arm 13' swing around the rotation spindle 18 and withdrawing the pawl from the ratchet 12. As is clear from Fig. 2, the ratchet is irrotationally attached to one of the two bevelled ends 4' of the rotation axle of the lever. Because both ends 4' of the rotation axle are mounted in the guide slot 8, the geared arc of the ratchet 12 cannot rotate. The translation lock, best illustrated in Fig. 3, is arranged to swing around a rotation axle 19 indicated by a dash-dotted line in Fig. 3. The translation lock 11 has a pawl 11 ' intended to cooperate with said gear for locking the hand brake in the chosen translational position, and a lever arm 20 which when subject to a force lifts the pawl 1 1 ' out of engagement with the gear tooth. The pawl 1 1 ' and the teeth of the gear are shaped so that the translation lock's pawl can move along the gear when the handbrake is applied, while the teeth and the pawl cooperate to lock it in the opposite direction. The rotation axle 19 of the translation lock is fastened by its ends in a part of the ratchet and in a holder 23, see Fig. 2. As mentioned above, the pawl 13 is immediately released from the ratchet on pressing the button 14. To release the translation lock 1 1, the lever must however be in its lowered position somewhat below the position shown in Fig. 2. This makes dynamic braking possible without the risk that the translation lock might release. The lever arm of the translation lock co-operates with a release rod 22 fastened on the lever where the lower end of the rod reaches the flat surface 20' of the lever arm first when the lever is in the position shown in Fig. 2. On continued lowering of the lever, the release rod 22 brings the lever arm 20 with it, whereby the translation lock is swung out of the locked position in the gear rack. A housing beam 24 is rotationally mounted on the rotation axle 4 of the lever 3. A force transmitter 25 is mounted in a guide slot 27 on the housing beam using a guide pin 26. Its shape, as well as the attachment of the housing 5 on the housing beam 24, is apparent from Figs. 4a, 4b and 4c. The one end region 46 of a wire link 47, the shape of which is apparent from Fig. 4b, is attached via said guide pin 26 to the rectangular part of the force transmitter 25. The end of the wire link 47 is thus mounted in the guide slot 27 on the housing beam. The opposite end 48 of the wire link is attached to the brake wire 9. The rod shaped part 28 of the force transmitter 25 extends into the housing and is attached to the force sensing mechanism in it. The latter is placed in the housing 5 as shown in Fig. 5 with the top removed to show the force sensing mechanism. It includes two arms 6 rotationally mounted on an axle peg (not shown) placed in the holes 29 in the walls of a fastener 30. The latter also has an external plug 30' with a threaded hole inside it. In it there is a threaded end part of the force transmitter's rod shaped part 28 whereby the fastener 30 is attached to the force transmitter and thereby via the wire link 47 also functionally to the brake wire 9. On the axle plug 30' and the said rod shaped part 28 a spring 31 is mounted which is compressed between the fastener 30 and the wall 32 of the housing 5. A tension force in the brake wire will therefore compress the spring. The force sensor is guided by the slot 33 in the housing and by guide pins (not shown) that extend through guide slots 34 in the respective arms 6 and are mounted in the bottom and top of the housing. The spring 31 is dimensioned so that it is not totally compressed before slack in the brake wire is taken up and appropriately not before the force in the wire exceeds a chosen value of the order of 70 N. The arms 6 rest in the position shown in Fig. 5 on the guide surfaces 7 of the housing holder as shown in Fig. 1. On compressing the spring 31 , the arms 6 are moved and drawn in toward the centre of the housing. This motion is controlled by the guide pins and the guide slots in which they cooperate. The arms and the spring are so designed that the arms completely glide off the side surfaces 7 of the housing holder when the spring is totally compressed. The arms are appropriately made of a plastic such as POM that gives low friction between the housing holder and the arms. The guide pin 26 that holds the force transmitter 25 and the wire link 47 together moves in the glide slot 27 in the upper part of the housing holder beam 24. During the motion of the guide pin along the glide slot, the end region 46 of the wire link will thus be guided along that slot as the spring 31 in the force sensing mechanism is compressed. The distance between the glide slit 27 and the centre of the rotation axle 4 of the lever 3 determines the force ratio on rotation of the lever for stretching the wire. A stop nipple 49 is arranged on the housing holder beam to cooperate with the wire link 47 to increase the force ratio when the lever is drawn through a large angle. Fig. 6 shows the design of the lever 3 and its attachment to the rotation axle 4, as well as the lever's and housing's 5 relative shapes that permit the said units to cooperate during translational and rotational motion. Functionally the brake according to the invention is significantly different to conventional mechanical parking brake systems. On drawing up the parking brake, the driver grasps the handle 15 and pulls it toward himself. In conventional parking brakes the hand brake lever immediately begins to rotate to first take up existing slack in the wire system. Only thereafter is force applied on continued rotation. When the hand brake shown in Fig. 1 is pulled, the lever does not rotate immediately but instead moves in the direction of the arrow A. Rotation of the lever is prevented by the arms 6 of the housing 5 which are in engagement with the locking surfaces 7 of the housing holder 1. During translational motion, the brake lever's motion is guided by the guide slots 2 of the housing holder 1 in which the rotation axle of the lever moves. The housing 5 and the force sensing mechanism mounted in it are moved translationally by the lever along the housing holder. When slack ~ in the wire system has been taken up and the force in the wire 9 has reached a value at which the spring in the force sensing mechanism begins to be compressed, the spring then begins to be pressed together and the whole force sensing mechanism is translated inside the housing at the same time as the housing is translated. As described above, the translation of the force sensing mechanism implies that the arms 6 are drawn in toward the centre of the housing and out of engagement with the locking surfaces 7 of the housing holder 1. When the arms 6 are completely within the walls of the housing holder, the motion of the lever and the housing upon continued activation of the lever changes from a translational motion to a rotation around the axle 4 which has now been displaced a little in the guide slot 8. The translational motion is hardly noticeable for the driver as the lever is normally only moved about 15 mm. In the first brake stage, during the translational motion, the force ratio is low, in the example shown 1: 1. In the second brake stage, during rotation, the brake lever changes automatically to a significantly higher ratio. For the parking brake according to the invention, the force ratio after taking up the wire slack is significantly higher than for known parking brakes. This means that the dimensions of the lever can be reduced significantly relative to known brakes. The lever is therefore easier to position and it is easier to achieve ergonomically good solutions. The direction of the guide slot 8 on the housing holder 1 that guides the translational motion can be chosen to give the ergonomically best pulling direction for the driver. To release the brake, the release button 14 is pressed, whereby the ratchet is immediately freed while the translation lock is in operation until the lever has reached or is near its resting position. This makes dynamic braking and adjustment of the braking power possible, which adjustment can be desirable in certain situations. The embodiment shown in Figs. 7- 10 functions in all major aspects in the same way as the parking brake in the embodiment described above. The parts have been given the same reference numbers in Figs. 8- 10 as corresponding parts in the above-described embodiment. In the following, only parts that are different to those in the above-described embodiment are treated briefly. In Fig. 7, it is primarily only the housing 5 and its attachment that are different. In this embodiment, there is no housing holder beam. Instead, the housing 5 is connected to the rotation axle of the lever 3. The housing 5, best shown in Fig. 8, has a pulley 35 along which the wire 9 runs to the fastener 30. In the closed position adjacent to the lever the housing is connected via splined couplings to the rotation axle of the lever which is located in the centre hole of the pulley 35. The lever is also attached using splined couplings. The lever rests against the angled wall 36 of the housing 5 for better support. The force ratio during the rotational motion is determined in this embodiment by the radius of the pulley and the length of the lever. Also in this embodiment there is a compression spring (not shown) attached between the wall 32 and the fastener 30 in the force sensing mechanism. The housing 5 is also equipped as shown with a cover intended to be placed over the housing to contain the force sensing mechanism. As is apparent from Fig. 9, the release button 14 is different and the associated link system is a little simpler in its construction. On releasing the parking brake, the button 14 is pushed in the direction of the arrow B whereby the ratchet 12 is immediately released. The translation lock can only be released when the lever is in or near its resting position. First in that position is it possible for the arm 37, which is moved clockwise by the plug 38 on pressing the release button 14, to reach the arm 39 of the translation lock 11 and press the translation lock out of engagement with the gear rack 40. The housing holder 1 shown in Fig. 10 is somewhat modified compared to the first embodiment. The wire enters under the housing in the housing holder and is diverted by a pulley (not shown) for fastening in the force sensing mechanism. In one end of the housing holder there is a guide slot 31 for the arms 6 of the force sensing mechanism. The invention is not limited to the above-described embodiments. Rather many modifications are possible within the scope of the appended claims.

Claims: CLAIMS 1. Arrangement for use in connection with a parking brake for a vehicle, including a lever (3) coupled to at least one force transmitting wire (9) in a brake system, characterised in that the lever (3), upon application, is arranged to work in two steps to achieve the intended brake power, in that in the first step the lever is arranged to make a translational movement for taking up wire slack in the brake system and in the second step the lever (3) is arranged to rotate, whereby force transmission to the wire (9) takes place at a higher ratio than during the first step. 2. Arrangement according to claim 1, characterised in that a force sensing mechanism is coupled to the wire (9), said mechanism comprising a locking pawl which is arranged to be released to allow said rotation first when the slack in the wire is taken up and the force in the wire exceeds a chosen value. 3. Arrangement according to claim 2, characterised in that a translation lock (11) is arranged to retain the lever (3) in its tightened translational position, in that a ratchet (12) is arranged to retain the lever (3) in its tightened rotational position and in that a release arrangement is arranged to release the translation lock and the ratchet, the release apparatus including a release button (14) attached to the lever (3), the release button operating via a link system in the lever on the locks (11, 12) to free them and the release apparatus being designed to first release the ratchet (12) and thereafter when the lever is in or near its rest position then release the translation lock. 4. Arrangement according to any one of the previous claims, characterised in that the apparatus includes a housing (5) in which the force sensing mechanism is situated, the said housing being placed in a housing holder (1) fixed to the vehicle, the lever (3) being rotatable on a rotation axle affixed in said housing holder (1), the housing (5) and lever (3) being positioned in direct contact with each other and arranged to cooperate so that only together can they be moved or rotated in the housing holder, the locking apparatus included in the force sensing mechanism being equipped with arms (6) that in the first brake step are arranged to prevent the housing (5) from rotating in the housing holder (1), the force sensing mechanism including a spring (31) so arranged that it is compressed by the force in the wire (9), the spring being dimensioned so that it is completely compressed first when the slack in the wire is taken up and the force in the wire exceeds said chosen value and the arms (6) being arranged to be released from locking engagement with the housing holder when the spring (31) is completely compressed. 5. Arrangement according to claim 4, characterised in that the housing's (5) translational motion is guided by at least one guide slot (2) in the housing holder (1). 6. Arrangement according to claim 5, characterised in that the parking brake is placed in the middle console of the vehicle beside the gear lever in order to achieve an ergonomically good solution when using the hand brake, and the direction of said guide slots (2) is chosen to achieve the ergonomically best possible pulling direction for the driver.

Inventors: MARKLUND PAER, SUNDQVIST FREDRIK, MARKLUND, PAER, SUNDQVIST, FREDRIK
Applicants: MARKLUND PAER, SUNDQVIST FREDRIK, VOLVO PERSONVAGNAR AB, MARKLUND, PAER, SUNDQVIST, FREDRIK
Application year: 1999
Main classification: B60T11
IPC codes: B60T11, F16C1, F16D55, F16D65