DE102006009089A1 - Drum brake e.g. simplex brake, for vehicle, has parking brake actuator actuated by electrical drive, where parking brake actuator presses two brake linings against brake drum for locking vehicle - Google Patents

Abstract

The drum brake has a wheel cylinder (5) arranged between an end (3b) of a brake lining (3) and an end (4b) of another brake lining (4). A parking brake actuator (6) is actuated by an electrical drive, where the parking brake actuator presses the two brake linings against a brake drum (2) for locking a vehicle. The electrical drive is arranged outside a casing, where the electrical drive is positioned inside the drum brake. The parking brake actuator has two pistons that are arranged opposite to each other in the casing.

Description

State of technology

The The present invention relates to a drum brake for a vehicle with an integrated, electrically operated parking brake.

drum brakes are of the prior art in different configurations known and are used as a combined service and parking brake. Drum brakes are available as simplex brake, duplex brake, duo-duplex brake, Servo brake or duo servo brake known. In today's vehicles are drum brakes especially on the rear axle of the vehicle arranged and formed predominantly as simplex brakes. The drum brakes be for a service brake while hydraulically via a wheel cylinder, which between two opposite ones Ends of each substantially crescent-shaped brake shoes arranged is, pressed. Simplex brakes are characterized by a moderate self-boosting and thereby also by a sufficient controllability for additional brake functions such as. ABS, ESP etc. off. With regard to the parking brakes used (Parking brakes) are in recent Time increases the conventional hand-operated Parking brakes with cable replaced by electric parking brakes. in this connection For example, so-called cable pullers have been proposed a shortened one Cable by means of a driven by an electric motor pulling device is actuated to detect the vehicle. A parking brake request a driver is doing over a button or switch in the vehicle interior to the electric motor given. However, such electric parking brakes have a large number of individual components and have due to the used cable pull mechanism a relatively low overall efficiency.

Advantages of the invention

The drum brake according to the invention for a Vehicle with the features of claim 1, in contrast, the Advantage that they have a compact, integrated in the drum brake parking brake actuator includes. As a result, the inventive combined operating and Parking brake on a compact and inexpensive construction. It is it for the use of the parking brake does not require a hydraulic pressure build. This can be avoided that when you press the Parking brake unwanted Sounds audible through the hydraulic pumps become. This is inventively characterized achieved that the drum brake two sickle-shaped brake shoes, a brake drum, a wheel cylinder for the service brake and a separate parking brake actuator for the parking brake having. The parking brake actuator is by means of an electric drive driven and out of the vehicle interior by means of a button or Switch enabled or disabled. The parking brake actuator is included arranged in the drum brake so that he has the two brake shoes for detecting the vehicle presses against the brake drums.

The under claims show preferred developments of the invention.

Of the Parking brake actuator is preferably between two ends of the first and arranged second brake shoe, wherein the parking brake actuator the wheel cylinder in the drum brake opposite. It it should be noted, however, that in principle also the wheel brake cylinder and the parking brake actuator are arranged side by side in parallel can, then both act on the same ends of the brake shoes.

Further Preferably, the parking brake actuator comprises a first and a second Pistons facing each other in a sleeve are stored. By means of the pistons the parking brake actuator brings one Parking brake force on the brake shoes of the drum brake. Depending on Design of the drum brake, the sleeve is fixed fixed or in Direction of its longitudinal axis freely movable (i.e., floating).

Around one possible To provide compact design, the electric drive is preferably immediate Outside on the sleeve arranged. Preferably, the electric drive is in the Interior of the drum brake.

Further Preferably, the parking brake actuator comprises a spindle with a first and second threaded portion, wherein the two threaded portions in opposite directions are formed. Further, the first piston is a first thread and a second thread provided on the second piston. By means of this Thread is the first piston with the first thread area and the second piston connected to the second threaded portion of the spindle. The spindle is driven by the electric drive and because the first and second threaded portion formed opposite to each other are, the two pistons move on the spindle in opposite directions. This allows a simple mechanism for the intervention and release of Parking brake can be realized.

Preferably, a transmission is arranged between the electric drive and the spindle. More preferably, the parking brake actuator comprises an expanding wedge which is perpendicular to the longitudinal axis of the first and second pistons between the first and second piston, and which acts on the opposite ends of the first and second pistons.

According to one another preferred embodiment of the present invention the vertically movable expanding wedge a first and second wedge surface. Of the Expanding wedge is perpendicular to the longitudinal direction of arranged on both pistons, each with a wedge surface a piston end acts. By a vertical movement of the wedge can Thus, a linear, horizontal movement of the two pistons in opposite Directions are provided. For automatic reset can elastic elements such as e.g. Springs on the pistons and / or brake shoes be provided.

Around one possible small operating force of To realize parking brake are between the piston ends and the wedge surfaces of the expanding wedge each arranged means for reducing friction. Such devices for friction reduction can, for example Rolling elements, e.g. Rolls, balls, etc., be or the wedge surfaces as well as the end surfaces of the Pistons have surfaces with little roughness on.

Further The drum brake according to the invention preferably comprises a device for pad wear compensation. For this purpose, a control device is provided which depends on a state of wear the brake pads a starting position of the pistons of the parking brake actuator changes. hereby Is it possible to dispense with a mechanical device for wear compensation, making the construction of the drum brake even easier and more compact becomes.

According to one another alternative embodiment of the present invention takes place an operation the piston of the parking brake actuator by means of articulated lever or cam or Eccentric.

The present invention can be used in drum brakes, which as a simplex brake, Duplex brake, duo-duplex brake, servo brake or duo servo brake are formed.

drawing

following Be exemplary embodiments of Invention described with reference to the accompanying drawings. In the drawing is:

1 a schematic view of a drum brake according to a first embodiment of the invention,

2 an enlarged view of a parking brake actuator of the drum brake of 1 and

3 an enlarged view of a parking brake actuator according to a second embodiment of the present invention.

description the embodiments

The following is with reference to the 1 and 2 a drum brake 1 described according to a first embodiment of the invention.

As in 1 shown, includes the drum brake 1 a brake drum 2 , a first crescent-shaped brake shoe 3 and a second crescent-shaped brake shoe 4 , The two brake shoes 3 . 4 are each with a brake pad 3a respectively. 4a Mistake. Furthermore, a wheel cylinder which can be activated by means of hydraulic pressure 5 between a first end 3b the first brake shoe 3 and a first end 4b the second brake shoe 4 intended. How farther 1 is apparent, is opposite the wheel cylinder 5 between the second end 3c the first brake shoe 3 and the second end 4c the second brake shoe 4 a parking brake actuator 6 arranged. The parking brake actuator 6 is intended for the determination of the vehicle at a driver's brake request, while the wheel cylinder 5 is used in a known manner for service braking of the vehicle. The drum brake 1 is thus a combined service and parking brake.

The parking brake actuator 6 is in detail in 2 shown. How out 2 can be seen, includes the parking brake actuator 6 an electric drive 7 , a first piston 8th and a second piston 9 , The electric drive 7 is activated via a button or switch arranged inside the vehicle, via which a driver can enter a parking brake request of the vehicle or a release of the parking brake. How out 2 it can be seen, the two pistons 8th . 9 in a sleeve 15 arranged on an axis XX opposite each other. The parking brake actuator 6 further comprises a spindle 10 with a first threaded area 11 and a second threaded area 12 , The first thread area 11 is in the opposite direction to the second thread area 12 educated. The spindle 10 is fixed with a gear 13 connected, which with a drive gear 14 which by the electric drive 7 is driven, is connected. The electric drive 7 is in a housing 17 arranged, which on the sleeve 15 it is fixed that it is inside the parking brake 1 protrudes. The sleeve 15 may alternatively be arranged stationary or floating, ie, be arranged linearly movable in both directions in the direction of the axis XX. The two pistons 8th . 9 are each by means of a warehouse 16 inside the sleeve 15 stored.

How out 1 shown have the first piston 8th and the second piston 9 one internal thread each 8a respectively. 9a on. Here is the internal thread 8a with the first thread area 11 and the internal thread 9a with the second threaded area 12 the spindle 10 engaged.

The function of the parking brake according to the invention is as follows. When a controller, not shown, the electric drive 7 activated, the spindle becomes 10 over the gear forming gears 13 and 14 set in rotation. The pistons 8th and 9 , which are arranged so that they can not rotate, are thereby moved in the linear direction of the axis XX. The piston becomes more precise 8th moved outward in the direction of arrow A and the piston 9 moved outward in the direction of arrow B. This will push the two pistons 8th and 9 the brake shoes 3 and 4 outward. If the brake pads 3a respectively. 4a with the brake drum 2 come into contact, the parking brake position of the drum brake is reached. The threads between the spindle 10 and the piston 8th . 9 are self-locking, so that a locking of the parking brake position is achieved automatically. When this parking brake position is reached, the electric drive 10 be turned off again. The drum brake 1 thus provides the parking brake position without it being necessary for the hydraulics to be above the wheel cylinder 5 is activated. By the arrangement of the parking brake actuator 6 opposite the wheel cylinder 5 Furthermore, the self-reinforcing effect of the drum brake can also be utilized for the parking brake function. If the vehicle is parked with a slope, eg on a slope, the self-reinforcing effect of the drum brake will be due to the vehicle's own weight. In addition, the simple and compact design without the use of a cable high efficiency for the parking brake actuator 6 will be realized. It is also possible according to the invention that the parking brake force is precisely metered and is also obtained with high accuracy.

It is also possible to realize a lining wear compensation continuously. For this purpose, wear of the lining by a change in a starting or starting position of the piston 8th and 9 be changed by the pistons 8th . 9 not completely retracted but stopped in a position defined by the existing lining wear.

To release the parking brake position of the drum brake, all you need is the electric drive 7 operated in the opposite direction, so that the two pistons 8th and 9 back in the 2 be reset shown starting position. A return spring, not shown, provides the two brake shoes 3 . 4 also back to the starting position.

Due to the self-reinforcing effect of the drum brake, the electric drive can 7 be made very small and compact. The design can be carried out to a predetermined minimum force, since the self-reinforcing effect, the contact pressure of the brake shoes 3 . 4 to the brake drum 2 strengthened. In normal service braking by means of the wheel cylinder 5 the brake shoes are supported 3 . 4 to the piston 8th . 9 and on the spindle 10 through the self-locking thread between the piston and spindle. Alternatively, it should be noted that when the electric drive 7 not used for the wear adjustment, the brake shoes 3 . 4 also at the ends of the sleeve 15 can support. It should also be noted that the self-locking thread on the spindle 10 can be waived if, for example, a separate mechanical locking device is provided. However, the locking by means of the self-locking thread is preferred because this can reduce the number of parts and the cost.

The following is with reference to 3 a drum brake according to a second embodiment of the invention described, wherein identical or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

The second embodiment substantially corresponds to the first embodiment, wherein, in contrast to the first embodiment, the parking brake actuator 6 is structured differently. The parking brake actuator 6 of the second embodiment comprises an expanding wedge 20 with a first wedge surface 21 and a second wedge surface 22 , The expanding wedge 20 is perpendicular to the longitudinal axis of the sleeve 15 arranged and is by a spindle drive in the vertical direction, as indicated by the double arrow C, movable. For this purpose, the expanding wedge 20 firmly at the end of a spindle 10 fixed, the spindle 10 with a mother 23 engaged. The electric drive 7 drives the mother 23 which causes the vertical movement of the spindle 10 , depending on the driving direction, is executed.

How farther 3 it can be seen are on the first piston 8th and on the second piston 9 each to reduce friction, a rolling element 24 respectively. 25 arranged. How out 3 it can be seen are the rolling elements 24 . 25 between the wedge surfaces 21 . 22 and the piston 8th . 9 arranged.

The function of the parking brake actuator 6 according to the second embodiment is as follows. If a driver a parking brake request by pressing a button or switch in Fahrzeu gereineren, is via a controller (not shown) of the electric drive 7 operated, so that the expanding wedge 20 is moved vertically downwards. Due to the oblique to the longitudinal axis of the piston 8th . 9 arranged first and second wedge surfaces 21 . 22 becomes the first piston 8th in the direction of the arrow A to the outside and the second piston 9 moved outward in the direction of arrow B. This will also be the two brake shoes 3 . 4 moved outward and their brake pads come into contact with the brake drum. As a result, a determination of the vehicle is achieved. Here is the thread between the nut 23 and the spindle 10 again designed self-locking, so that automatically locking the parking brake position is achieved. Alternatively, a separate mechanical lock could be provided.

To release the parking brake is only the electric drive 7 driven in the opposite direction, so that the expanding wedge 20 is moved vertically upwards again. As a result, for example via a return spring element again a provision of the piston 8th . 9 and the brake shoes 3 . 4 in the in 3 shown starting position.

Also in the second embodiment, a continuous pad wear compensation in the parking brake actuator 6 to get integrated. For this purpose, only a control must be provided such that the starting or starting position of the piston 8th . 9 is changeable. That is, when a pad wear has occurred, no longer a full recovery of the expanding wedge is in the starting position, but in a dependent on the size of the pad wear by a control predetermined position before the original starting position. The wear of the lining can be compensated steplessly.

It should be noted that the expanding wedge 20 instead of two wedge surfaces may also be designed as a cone. Also, the expanding wedge can be moved vertically by means of a spindle drive by means of eccentric or toggle lever.

Otherwise corresponds to this embodiment the previous embodiment, so that reference can be made to the description given there.

Claims (12)

Drum brake for a vehicle, comprising a first brake shoe ( 3 ) with a first brake pad ( 3a ), a second brake shoe ( 4 ) with a second brake pad ( 4a ), a brake drum ( 2 ), a wheel cylinder ( 5 ) for a service brake of the vehicle, which between a first end ( 3b ) of the first brake shoe ( 3 ) and a first end ( 4b ) of the second brake shoe ( 4 ), and a parking brake actuator ( 6 ) for a separate parking brake, which by means of an electric drive ( 7 ) is operable and the first and second brake shoe ( 3 . 4 ) for detecting the vehicle against the brake drum ( 2 ) presses. Drum brake according to claim 1, characterized in that the parking brake actuator ( 6 ) between a second end ( 3c ) of the first brake shoe ( 3 ) and a second end ( 4e ) of the second brake shoe ( 4 ) is arranged. Drum brake according to claim 1 or 2, characterized in that the parking brake actuator ( 6 ) a first piston ( 8th ) and a second piston ( 9 ) which lie opposite one another in a sleeve ( 15 ) are arranged. Drum brake according to claim 3, characterized in that the sleeve ( 15 ) is fixed in place or that the sleeve ( 15 ) is arranged freely movable in the direction of its longitudinal axis. Drum brake according to claim 3 or 4, characterized in that the electric drive ( 7 ) on the outside of the sleeve ( 15 ) is arranged and in particular directed into the interior of the drum brake. Drum brake according to one of the preceding claims, characterized in that the parking brake actuator a spindle ( 10 ) with a first threaded area ( 11 ) and a second threaded area ( 12 ) and the first piston ( 8th ) a first thread ( 8a ) and the second piston ( 9 ) a second thread ( 9a ), wherein the first thread ( 8a ) with the first threaded area ( 11 ) of the spindle ( 10 ) is engaged and the second thread ( 9a ) with the second threaded area ( 12 ) of the spindle ( 10 ) is engaged, and wherein the spindle ( 10 ) with the electric drive ( 7 ) and the first threaded area ( 11 ) in opposite directions to the second threaded area ( 12 ) is trained. Drum brake according to claim 6, characterized in that the parking brake actuator ( 6 ) a gearbox ( 13 . 14 ), which between the electric drive ( 7 ) and the spindle ( 10 ) is arranged. Drum brake according to one of claims 1 to 5, characterized in that the parking brake actuator ( 6 ) an expanding wedge ( 20 ) which is perpendicular to the longitudinal axis of the first and second pistons ( 8th . 9 ) is arranged between the first and second pistons, and which on the opposite ends of the first and second pistons ( 8th . 9 ) acts. Drum brake according to claim 8, characterized in that the expanding wedge ( 20 ) a first wedge surface ( 21 ) and a second wedge surface ( 22 ), wherein the first wedge surface ( 21 ) on the first piston ( 8th ) acts and the second wedge surface ( 22 ) on the second piston ( 9 ) acts. Drum brake according to claim 8 or 9, characterized in that the first piston ( 8th ) and the second piston ( 9 ) each at their to wedge ( 20 ) ends a device ( 24 . 25 ) for friction reduction, in particular a rolling element having. Drum brake according to one of the preceding claims, characterized by a control device for stepless compensation of wear of the brake linings of the brake shoes, wherein the control device, depending on an amount of wear, a starting position of the parking brake actuator ( 6 ) changes. Drum brake according to one of the preceding claims, characterized in that the parking brake actuator ( 6 ) as an actuating element for actuating the brake shoes ( 3 . 4 ) for the detection of the vehicle includes a toggle or a cam or an eccentric.