A large number of suggestions for electrically manoeuvred parking brakes for replacing conventional hand controlled parking brakes are known. Electrically manoeuvred hand brakes are described for instance in GB 2 304 838 A, WO/92 21 542 and EP 0398 546 A2.

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's position and send control signals to a first electric motor arranged to drive the said tightening means for generating a braking force corresponding to the position of the knob, the knob being manually adjustable and in its fully tightened position, at maximal braking force, capable of being locked mechanically, a control motor arranged to automatically manoeuvre the knob to its fully tightened and locked position in response to incoming control signals and in its fully tightened locked position it being possible to release the knob from its locked position only through manual operation.

The present invention has the following advantages: The great advantage of the knob as a manoeuvring means in an electrical hand braking concept is its size. Because it is small compared 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 manoeuvre 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 manoeuvring 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 manoeuvre.

In the following the invention will be described in more detail with reference to embodiments shown in the attached drawings.

Fig. 1 shows schematically a section through a car to illustrate appropriate positioning of the main parts of the parking brake according to the invention.

Fig. 2 shows the important parts of a unit for activating the two brake units of a pair of wheels with the said activation unit in a position such that the parking brake is released. Fig. 3 shows the unit according to Fig. 2 in a position such that the parking brake is applied. Fig. 4 shows some further details of the unit according to Figs. 2 and 3. Figs. 5 and 6 show the unit according to Figs. 2-4 viewed from the side to illustrate a mechanism for manual mechanical release of the parking brake. Fig. 7 shows an exploded view of an energy storage spring included in the unit according to Figs. 2-6. Fig. 8 shows an appropriate electrical diagram for the parking brake. Figs. 9 and 10 show exploded views of a knob according to the invention seen in different perspectives. Fig. 11 shows the automatic control of the knob schematically.

In Fig. 1 a plastic box is designated 1. In it there is 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 is designated 8. It is used to release the brake in case of current failure or other electrical fault.

A slide plate 9 is shown in Fig. 2. It is adjustably located in slide rails 10,11 and is attached at either end to a first and a second brake wire 2,3. On the slide plate there is an electric motor 12 (Fig. 4) which, via its gearbox, drives a lever arm 14 rotatably attached to the slide plate. Its rotational axis is designated 15 in the drawings.

On the free end of the lever arm 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 via a wire tensioner 38 and a spring package in which there is an energy storage spring 18 connected to the slide plate. The wire tensioner 38 can be equipped with a strain gauge (not shown). In the spring package there is a cylinder 19 containing the said spring. 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 part 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's 22 second shank 25 lies against the lever arm peg 16 which projects above the other shank. In Fig. 3 the lever arm 14 has swung from its unloaded original position shown in Fig. 2 in which the lever arm rests against a stop lug 26.

In the position of the lever arm shown in Fig. 3 the spring package with the spring 18 is held in position on the slide plate 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. The lock is lifted against the action of a pressure spring 28 out of its locking position on pulling the release wire 8. This manual mechanical release mechanism is described in more detail below in connection with Figs. 5 and 6. On the slide plate there is a number of microswitches. A first one 29 that indicates the original position of the lever arm peg 16, a second one 30 that indicates the final position of the lever arm peg and a third one 31 that 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 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 and the reaction force is taken up by the second wire 3 whereby the same force is always applied to the two wires. 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 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 centre 15 of the lever arm, whereby the lever arm is pressed against the stop lug 26 and held in that self locking position. The system is adjusted so that a force somewhat greater than necessary is applied to the wires. The energy storage spring which is pre-compressed 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 can be returned to its original position by the electric motor 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 because of a flat 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 by pulling the release wire 8 whereby the cylinder 19 is released and 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 when it is freed comprises a connection between the energy storage spring and the lever arm of the electric motor.

When the electric motor is again functional and the lever arm returns to its original position, the return 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 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 and in applied position extend out of the holes 35 in the outer cylinder for co-operation with the lock 27, a pre-stressing 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 the rod can slide in the central hole in the stop.

The purpose of the spring 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 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, the activation unit of the brake is contained in a plastic box 1, Fig. 1, and attached to a chassis plate (not shown) equipped with a wire guide, not shown, to guide the wires 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 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 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 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 the components of the brake's automatic system that is 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.

The microswitch 30 that indicates applied brakes and the microswitch 29 that indicates released brakes are connected to the control unit. Further, signals from a sensor 41 in the ignition lock, which sensor indicates key in or key out, and signals from a presence detector 42 in the driver's seat, which presence detector, for instance comprising 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 microswitch 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 are the following cases: -No driver in the driver'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 This is realised 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 Also 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 does 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 (not round) 53 is axially affixed to the rotation centre of the knob 6. The axle has a spring hole 54 for the pressure spring 55.

The (not round) axle 53 is displaceably arranged in a sliding sleeve 56 which passes through the lower plate 52 and which has a hole that fits the (not round) axle. 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 and that are arranged to run in a slot 59 in the housing. This slot is suitably long enough so that the knob can be rotated of the order of 100 degrees between its released and fully applied positions. The housing has an L-shaped groove part 60 arranged so that the guide pins are opposite that guide part when the knob 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 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 from its released position to its said fully applied position.

When the knob is fully tightened the knob 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 has been pressed axially to the bottom of the groove part 60, the torsion spring 61 forces the knob to rotate backward a little whereby the guide pins 67 go into a locked position in the L-shaped groove.

To bring the knob out of its locked position, which corresponds to a fully applied parking brake, the knob must first be rotated a little against the action of the torsion spring and thereafter moved axially against the pressure spring. This results in very good child safety.

The position of the knob is sensed by a rotary potentiometer (not shown) arranged to 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 manoeuvres 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'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's seat. When the driver leaves the driver'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 bringing the knob to its locked position. The manoeuvre 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 invention is not restricted to the above described embodiments. Rather, many modifications are possible within the scope of the appended claims. 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.