Abstract:
A knob arrangement for operating parking brakes intended for use in vehicles comprising brake units and an electrically operated tensioning device for applying or releasing braking force to the brake units. According to the invention, a device is arranged to sense the position of the knob and to send control signals to a first electric motor which is arranged to power the tensioning device for generating a braking force corresponding to the position of the knob. The knob is manually adjustable and, in a fully applied position, at maximum braking force, mechanically lockable. A control motor is arranged to automatically displace the knob to the fully applied and mechanically locked position dependent on second control signals applied to the motor. In its fully applied, locked position the knob is only releasable from the locked position by manual operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation patent application of International Application Number PCT/SE99/01743 filed Oct. 1, 1999 which designates the United States; the disclosure of that application is expressly incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the invention. The present invention relates to a knob arrangement for operating parking brakes intended for use in vehicles comprising brake units such as drum brakes or disc brakes on two opposing wheels in a pair of wheels, and an electrically operated tightening means for applying or releasing braking force to said brake units. 
     Background Information. A large number of suggestions for electrically maneuvered parking brakes for replacing conventional hand controlled parking brakes are known in the art. For instance, electrically maneuvered hand brakes are described in GB 2304838 A, WO/9221542 and EP 0398546 A2. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to achieve an electrically operated parking brake offering a number of advantages compared to previously known designs. According to the invention this is achieved primarily by a means, suitably a rotary potentiometer, being arranged to sense the knob&#39;s position and send control signals to a first electric motor. The electric motor drives a tightening means, or tightener, for generating a braking force corresponding to the position of the knob. The knob is manually adjustable, and in its fully tightened position, at maximal braking force, capable of being locked mechanically. A control motor is arranged to automatically maneuver the knob to its fully tightened and locked position in response to incoming control signals. In its fully tightened and locked position, it is possible to release the knob from its locked position only through manual operation. 
     The present invention has several advantages, including the following. A great advantage of the knob as a maneuvering means in an electrical hand braking concept is its size. Because it is small in comparison to a traditional lever, it can be placed, for instance, in the middle console of the instrument panel thereby freeing room between the front seats of the car. Another advantage is that the control consists of few parts meaning that production costs can be kept low. 
     The maneuver force needed for the knob is significantly lower than is the case for conventional hand brakes. This means that a weak person will have no problem releasing an activated parking brake. 
     The risk of forgetting to set the hand brake on leaving the car is eliminated through an automatic application function on the knob control. 
     Because it is easy to design the knob/knob control as an independent unit that fits as a module in different car models, the number of variations of maneuvering units for different car models is reduced. 
     In static application, the function that entails moving the control axially and returning it a number of degrees increases child safety. 
     The knob functions well in dynamic braking because it is easy to maneuver. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In the following detailed description, the invention will be described in more detail with reference to various embodiments shown in the attached drawings, comprised of the following figures. 
     FIG. 1 is a schematic of a section through a car illustrating appropriate positioning of the main parts of the parking brake according to the present invention. 
     FIG. 2 is a top perspective view of the brake activation unit for activating the two brake units of a pair of wheels with the said activation unit in a position illustrating a released parking brake. 
     FIG. 3 a top perspective view of the brake activation unit according to FIG. 2 in a position illustrating an applied or set parking brake. 
     FIG. 4 is a side perspective view providing further details of the brake activation unit according to FIG. 3 without the guide rails. 
     FIG. 5 is a side plane view of the brake activation unit according to FIG. 2 illustrating a mechanism for manual mechanical release of the parking brake when the brake has just been released. 
     FIG. 6 is a side plane view of the brake activation unit according to FIGS. 2 illustrating a mechanism for manual mechanical release of the parking brake when the parking brake has been deactivated. 
     FIG. 7 is an exploded perspective of an energy storage spring package included in the brake activation unit according to FIG.  2 . 
     FIG. 8 illustrates one example of an appropriate electrical diagram for the parking brake according to the present invention. 
     FIG. 9 is an exploded perspective from more of a top view of a knob according to the present invention. 
     FIG. 10 is an exploded perspective from more of a bottom view of a knob according to the present invention. 
     FIG. 11 is a schematic illustration of the automatic control of the knob according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     In FIG. 1 a plastic box  1  is illustrated having therein a brake activation unit. From that unit brake wires  2 ,  3  extend to brake units in the two wheels  4 ,  5 . A knob  6  for operating the parking brake is arranged in the middle console of the car. The knob  6  and the activation unit in the plastic box  1  are coupled to an electric control unit  7 . A mechanical release wire  8  available for manually releasing the brake in case of current failure or other electrical fault. 
     Referring to FIG. 2-4, a slide plate  9  is shown. It is adjustably located in slide rails  10 ,  11  and is attached at one end to a first brake wire  2  and a second brake wire  3 . On the slide plate  9  there is an electric motor  12  that, via its gearbox, drives a lever arm  14  rotatably attached to the slide plate  9 . Its rotational axis is designated  15  in the drawings. On the free end of the lever arm  14  there is a projecting lever arm peg  16  to which the first brake wire  2  is attached. The other brake wire  3  is coupled to the slide plate  9  via a wire tensioner  38  and a spring package in which there is an energy storage spring  18  (see also FIG. 7) connected to the slide plate  9 . The wire tensioner  38  can be equipped with a strain gauge (not shown). 
     In the spring package there is a cylinder  19  containing the spring  18 . It is displaceably located in a cylinder guide  20  and attached by one end to a shank  21  on a bent rod in the following designated return  22 , the middle pan  23  of which is displaceably attached to the slide plate  9  in a return holder  24 . The return  22  has a second shank  25  on the other side of the lever arm peg  16  relative to the outer cylinder  19  of the spring package. 
     In the position shown in FIG. 2, the return&#39;s  22  second shank  25  lies against the lever arm peg  16 , which projects above the other shank. In FIGS. 3 and 4, the lever arm  14  has swung from its unloaded original position shown in FIG.  2  and rests against a stop lug  26 . In the position of the lever arm  14  shown in FIGS. 3 and 4, the spring package with the spring  18  is held in position on the slide plate  9  only by the lock  27 , which in its normal position, the locked position, retains the outer cylinder  19  and takes up the tension in the other wire  3 . Upon pulling the release wire  8 , the lock  27  is lifted against the action of a pressure spring  28  out of its locking position. This manual mechanical release mechanism is described in more detail below in connection with FIGS. 5 and 6. 
     On the slide plate  9  there is a number of micro-switches. A first one  29  indicates the original position of the lever arm peg  16 , a second one  30  indicates the final position of the lever arm peg, and a third one  31  indicates when the brake is mechanically released by means of the release wire  8 . 
     The parking brake is released when the activation unit is in the position shown in FIG.  2 . The electrical motor  12  is arranged to swing the lever arm  14  on activating the brake, whereby the lever arm peg  16  performs a clockwise rotational movement from its original position to its final position while simultaneously pulling the first wire  2  to stretch it. The slide plate  9 , which is arranged to slide in the slide rails  10 ,  11 , is moved by the first wire  2 , with the reaction force taken up by the second wire  3 . Accordingly, the same force is always applied to the two wires  2 ,  3 . The gearbox of the electric motor  12  is self-braking, which means that the lever arm  14  can be stopped and held in any position. This makes dynamic braking with the parking brake possible. 
     When the vehicle is to be parked, the lever arm  14  is drawn to its final position as shown in FIGS. 3 and 4. In that position, the lever arm peg  16 , and therefore the force vector of the wire  2 , has passed the rotational center  15  of the lever arm  14 , pressing the lever arm  14  against the stop lug  26  and holding it in that self-locking position. The system is adjusted so that a force somewhat greater than necessary is applied to the wires  2 ,  3 . The energy storage spring  18 , which is precompressed to the necessary application force, is thereby further compressed to compensate for force changes that can occur, for example, in connection with cooling of the brake discs. When the parking brake is applied, the lever arm  14  can be returned to its original position by the electric motor  12  in order to release the brake. 
     As mentioned above, in the activation unit there is a manual mechanical release mechanism with which the parking brake can be released if the electric motor does not work, for instance, due to a dead battery. The function of the release mechanism is most clearly apparent from FIGS. 5 and 6. In FIG. 5, the lock  27  has been lifted up out of engagement with lock pegs  32  on the outer cylinder  19  by pulling the release wire  8 , whereby the cylinder  19  is released. The spring package can now be brought out of its previously fixed position shown in FIG. 5 by the force of the wire. When the cylinder slides in the cylinder guide  20 , the slide plate  9  is also moved until the wires  2 ,  3  slacken and the parking brake is released. 
     The return  22  described above, which moves with the outer cylinder  19  when it is freed, comprises a connection between the energy storage spring and the lever arm  14  of the electric motor  12 . 
     When the electric motor  12  is again functional and the lever arm  14  returns to its original position, the return  22  is pressed back by the lever arm plug  16  and the cylinder  19  is brought back to its original position as shown in FIG.  5 . In that position the pressure spring  28  forces the lock  27  to engage against the outer cylinder. The parking brake is thus automatically made functional when the manual mechanical release mechanism is used and the electric motor  12  is again functional. A significant advantage of this is that the vehicle does not need to be driven to a garage each time the release mechanism has been used. 
     The spring package according to FIG. 7, which as mentioned above is placed on the slide plate  9  and in terms of force connected to the other wire  3 , consists of the outer cylinder  19 , a rod  33  placed therein, the spring  18 , a stop  34 , the lock pegs  32  which are fastened to the stop  34  and in applied position extend out of the holes  35  in the outer cylinder for co-operation with the lock  27 , a prestressing nut  36 , a lock nut  37  and a wire tensioner  38 , one end of which can be screwed tightly to the rod  33  and the other end of which is intended to be connected to the other wire  3 . If the force in the wire  3  exceeds the force in the spring  18 , the rod  33  can slide in the central hole in the stop  34 . 
     The purpose of the spring  18  is to store energy for thermal changes and to be a position and energy reserve for relaxation in the system. The demands placed on the spring  18  are that it shall store energy from the forces that exceed the minimal locking force. Additionally, it shall be possible to deform it by an amount of the order of 5 mm. 
     As mentioned above and referring again to FIG. 1, the activation unit of the brake is contained in a plastic box  1  and attached to a chassis plate (not shown) equipped with a wire guide, not shown, to guide the wires  2 ,  3  correctly in relation to the slide plate  9 . The whole activation unit with the chassis plate and surrounding plastic box  1  is easy to place in the vehicle. For the shortest wire routing, it is appropriately placed between the back wheels  4 ,  5  as shown in FIG.  1 . The construction is well suited to positional control with the help of a knob according to the invention, since the lever arm  14  has a restricted rotational displacement, in the order of 0-195 degrees. Positional control is an advantage during dynamic braking. 
     Manually the parking brake is activated by turning the knob  6 , which is appropriately placed in the middle console of the instrument panel. Deactivation is achieved by pressing the knob and rotating it back to its original position. For dynamic braking, the knob  6  can be turned continuously between released and fully applied. 
     The braking system is designed for a number of automatic functions. It shall be possible to apply the parking brake automatically when certain chosen conditions for the respective functions are fulfilled. The electrical diagram is shown in FIG. 7 with those components of the brake&#39;s automatic system that are controlled by the control unit  7 . It is coupled via an ammeter  39  to the electric motor  12  and a potentiometer  40 , which is a comparator for the position of the lever arm  14 . 
     The micro-switch  30  that indicates applied brakes and the micro-switch  29  that indicates released brakes are connected to the control unit  7 . Further, signals from a sensor  41  in the ignition lock, which indicates key in or key out, and signals from a presence detector  42  in the driver&#39;s seat such as a weight sensor, indicates whether there is a driver in the seat or not, are fed to the control unit  7 . A torque sensor  43  provides information on when the motor is running. A micro-switch  31  indicates whether manual mechanical release has taken place. Information corresponding to the force in the wire is given to the control unit from a strain gauge  17 . 
     A rotary potentiometer  48  is arranged to detect the position of the knob and send control signals proportional to the angle of the knob to the control unit  7  for continuous control of the brake force. The system also includes at least one end position sensor  49  for the knob, a sensor  50  in the door locks and sensors in the gear lever and brake pedal. 
     There are times when the brake must not release automatically. Examples include the following cases: 
     No driver in the driver&#39;s seat 
     The motor is running 
     The vehicle has been hit 
     There is no voltage or the voltage has just been applied 
     Electrical failure, short circuit 
     These cases may be realized using the sensor in the chair while the motor does not signal powering the vehicle. 
     The brake shall be applied automatically in the following cases: 
     When the car rolls backward 
     A forward gear (first gear) is engaged 
     The car rolls forward 
     Reverse gear is engaged 
     When the ignition key has been removed 
     Here, the sensor in the ignition lock is used. The control unit must also have information from the sensor in the gearbox for identification of the gear engaged, while the ABS system of the car provides the information that the car is in motion. 
     Further, it is important that the brake not apply itself in the following situations: 
     When being towed 
     When a wheel locks while the car is moving 
     When there is an electrical failure 
     It is therefore important to be able to disconnect the automatic control. 
     The knob according to the invention is described in the following with reference to FIGS. 9-11. The knob  6  is placed in a housing  51  attached to a lower plate  52 . An axle  53  (not round) is axially affixed to the rotation center of the knob  6 . The axle  53  has a spring hole  54  for the pressure spring  55 . The (not round) axle  53  is displaceably arranged in a sliding sleeve  56  that passes through the lower plate  52  and that has a hole that fits the (not round) axle  53 . Rotation of the axle  53  relative to the sliding sleeve  56  is thereby prevented. 
     The knob  6  has two projecting guide pins  67  that are brought into the openings  58  when the knob is brought into the housing  51  and that are arranged to run in a slot  59  in the housing  51 . This slot  59  is suitably long enough so that the knob  6  can be rotated in the order of 100 degrees between its released and fully applied positions. The housing  51  has an L-shaped groove part  60  arranged so that the guide pins  67  are opposite that guide part when the knob  6  has been rotated to the fully applied position. 
     When the guide pins  67  move in the slot  59 , the pressure spring  55  is loaded and presses the knob upward. There is a torsion spring  61  between the knob  6  and the lower plate  52 . The torsion spring  61  is attached between the spring holders  62  and  63  on the knob  6  and the lower plate  52 , respectively, and arranged to oppose rotation of the knob  6  from its released position to its said fully applied position. 
     When the knob  6  is fully tightened, it is pressed axially upward by the pressure spring  55  whereby the guide pins  67  move in the L-shaped groove part  60 . When the knob  6  has been pressed axially to the bottom of the groove part  60 , the torsion spring  61  forces the knob  6  to rotate backward a little whereby the guide pins  67  go into a locked position in the L-shaped groove. 
     To bring the knob  6  out of its locked position, which corresponds to a fully applied parking brake, the knob  6  must first be rotated a little against the action of the torsion spring  61  and thereafter moved axially against the pressure spring  55 . This results in very good child safety. 
     The position of the knob  6  is sensed by a rotary potentiometer (not shown). This potentiometer is arranged to both sense the rotation of the sliding sleeve  56  and send control signals to the electric motor  12  for proportional rotation of the lever arm  14  for tightening or releasing the brake wire  2 . 
     As mentioned above the parking brake has a number of automatic functions. For example the parking brake is set automatically when the key is taken out of the ignition lock. 
     To correctly show that the parking brake has been activated, there is included in the invention a control motor  64  that starts automatically and maneuvers the knob to the fully applied mechanically locked position. This function is shown schematically in FIG.  11 . The control motor, 64  powers a conical gear  65 . It is arranged to engage and disengage gear teeth  66  on the knob  6  via a solenoid. The solenoid&#39;s displacement of the gear  65  is controlled by the control unit depending on input signals from sensors. Examples of such sensing functions are a sensor in the ignition lock and a presence detector in the driver&#39;s seat. When the driver leaves the driver&#39;s seat and when the key is taken out of the ignition lock these sensors produce control signals for applying the parking brake and, simultaneously via the control unit, also produce control signals to the solenoid for moving it so that the gear engages the gear wheel on the knob thereby bringing the knob to its locked position. The maneuver knob  6  is appropriately somewhat larger that other controls on the instrument panel. For comfortable use, a control knob diameter of altogether about 7 cm is appropriate. 
     The electric braking unit can be of a different type to that which has been described above in connection with FIGS. 2-7. For example, the braking units need not be activated by wires but can be electromechanical brakes applied directly to the respective wheel. 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be restricted to the above described embodiments. Rather, many modifications are possible within the scope of the appended claims.