DE3732303A1 - Hydraulic brake-actuating system - Google Patents

Abstract

A description is given of a hydraulic brake-actuating system for a friction brake, which is equally suitable for service braking operations and parking. The actuating system comprises a brake cylinder (20) with two opposed brake pistons (21, 22), the mutually facing end faces of which form wedge faces (32, 33) inclined relative to the axis of the brake cylinder (20). Provided between the brake pistons (21, 22) is a locking wedge (31) which can be placed against the wedge faces (32, 33). The locking wedge is actuated by a locking-mechanism piston (34) arranged in a locking-mechanism cylinder (35) and projecting radially into the cylinder chamber (41). To lock the brake pistons (21, 22), the locking-mechanism piston (34) is subjected to the brake pressure in the brake-actuating position and the locking wedge (31) is thereby pushed between the wedge faces (32, 33). During the subsequent pressure reduction, the locking wedge (31) holds the brake pistons (32, 33) in their brake-actuating position owing to the frictional engagement existing. <IMAGE>

Description

The invention relates to a hydraulic actuating device device for a friction brake, especially for special forces vehicles with a brake cylinder and at least one in Brake cylinder axially movable brake piston for pressing a Friction body on a braking surface.

Such hydraulic brake actuators are in the general use for temporary service braking which are monitored by an operator. A such braking is, for example, braking one Vehicle while driving or standing, the Driver during the entire duration of the braking process Brake pedal operated. For a longer lasting, automatic Apply a friction brake, for example to park the Vehicles on an uphill or downhill slope are hydraulic brake actuators because of the risk of a Brake pressure drop not suitable. It is therefore for parking additional, so-called parking brake devices featured see the mechanical links for permanent pressing Have friction bodies on the braking surfaces. This leads to a ver equally high construction costs for a brake system.

The invention is therefore based on the task of construction for a brake system and a hydraulic one Brake actuator of the type mentioned create that for service braking and at the same time to Locking the brake in the braking position is suitable.

This object is achieved in that between hydraulic brake piston and an abutment  actuatable, self-locking locking mechanism is provided by the brake piston in the brake release direction on the abutment is supported. With such a hydraulic actuator device for a friction brake can the brake piston mechanically when braking in the braking position be locked so that the brakes even after dismantling the brake pressure acting on the brake piston remains applied. One with the actuating device according to the invention equipped friction brake can therefore be used equally as an operating brake and serve as a parking brake, where it turns out to be proves particularly simple that pressing the lock brake also by hydraulic control of the actuators supply device takes place.

According to one embodiment of the invention it is provided that the ratchet one transverse to the longitudinal axis of the brake cylinder Movable locking wedge, which with a wedge surface the back of the brake piston and / or on the abutment together works and its wedge angle in the area of self-locking lies. Such a design of the locking mechanism is simple and robust and enables the support of high forces.

According to the abutment by a second Brake piston formed for actuating a second friction body be. Such a configuration of the brake cylinder is suitable especially for actuating the two brake shoes Drum brake or to operate a twin disc brake, with the brake cylinder between the two brakes discs are arranged.

To actuate the locking wedge, in a further development of the Er a locking cylinder with a locking mechanism piston be provided radially to the brake cylinder  connected. The ratchet piston is preferably as Step piston formed and protrudes with its smaller piston level in the pressure chamber of the brake cylinder, where it is firmly connected to the locking wedge. That way forms the ratchet piston a safe guide for the ratchet. In addition, the small piston stage is the pressure in the brake cylinder the acted upon, which, when the sole actuation of the Brake cylinder of the locking wedge held in its release position can be. Accidental brake application sole control of the brake cylinder during one Service braking is done in this way with simple means reliably avoided. It is still an advantage that the ratchet piston to the blunt end of the ratchet is connected, as this results in the axial length of the Brake cylinder can be kept small.

According to the invention it is further provided that the locking wedge between its opposite wedge surfaces by part cylinder surfaces is limited, the curvature of the curvature corresponds to the cylinder bore of the brake cylinder. These Design leads to optimal use of the im Inside the brake cylinder for the locking wedge available standing installation space and thus enables sufficiently large Wedge surfaces to absorb the brake actuation force. Are located in the area of the partial cylinder surfaces of the blocking wedge Mün of connecting holes in the brake cylinder, so can the partial cylinder surfaces there according to the invention to have.

According to a further advantageous embodiment of the Erfin can be in an annular housing over the circumference distributed, several from the brake cylinder and locking cylinder existing, uniform actuation units arranged be connected to each other via pressure and control line  are. Such an actuator is suitable especially for actuating full disc brakes where the actuator between two annular friction body is arranged in the opposite direction are each articulated on a separate brake disc. Such Solid disc brakes are preferred in heavy chain driving witness used.

According to the actuation units in the ring shaped housing arranged so that their locking cylinder are directed upwards with respect to a horizontal plane and extend circumferentially. This will make one compact design achieved and venting the Gesperrezy relieved. In further development of this inventive concept kens can be provided in this arrangement that the Brake cylinder two ver at an acute angle to each other have running connection bores that are in a common, each connection channel above the cylinder bore flow out. Such a configuration enables the installation of Brake cylinders in four different angular positions, in which the Mouth of a connection hole at the highest point of the Cylinder bore is located to vent the brake cylinder guarantee. It can therefore be done with a single off leading one of the best brake cylinder and locking cylinder existing actuator without disadvantage four different Installation positions to create an annular cylinder arrangement realization.

For cooling the arranged in the annular housing Actuating units can also be pre-invented can be seen that the interior of the annular housing of a coolant can flow through. Too much warming the actuation units lying between two friction rings can be effectively prevented.  

According to a further proposal of the invention Operation of one or more brake cylinders an operation brake valve and for actuating one or more locking mechanisms A parking brake valve can be provided through the cylinder the brake cylinder or the locking cylinder with one pressure loose container or can be connected with a pressure wave. Preferably, the parking brake valve between the Service brake valve and the brake cylinder are switched to via the parking brake valve in the event of a fault To enable emergency actuation of the brake cylinder. Here it is still cheap if the service brake valve and the fixed Parking brake valve to independent pressure medium sources are connected.

A particularly advantageous and avoiding incorrect control Design of the parking brake valve is according to the invention thereby achieved that the parking brake valve the brake cylinder in a first switching position with the output of the Service brake valve, in a second and third switching position with one connected to the parking brake valve Pressure medium source and in a fourth switching position a return line and the locking cylinder in the first, second and fourth switching position with the return line and ver in the third switch position with the pressure medium source binds.

The operation of the hydraulic actuator after of the invention by controlling brake valves that are connected to a Pressure medium source are connected has the advantage that a plurality of relatively large-volume brake cylinders with low effort can be operated simultaneously. Nevertheless, with a correspondingly low number of cylinders, the Actuation of the brake cylinder and the locking cylinder also with With the help of directly or indirectly operated master brake cylinders respectively.  

The invention is illustrated below with the aid of an embodiment game explained in more detail, which is shown in the drawing.

Show it:

Fig. 1 cylinders is a cross section through an inventive full-lined disk brake with hydraulic brake,

Fig. 2 shows a section along the line II-II through the full lining disc brake according to FIG. 1 and

Fig. 3 is a circuit diagram of a hydraulic Bremsbetäti purification system for actuating the full disc brake shown in FIGS. 1 and 2.

The full lining disc brake shown in FIGS . 1 and 2 is intended for installation in a tracked vehicle. The brake consists of a pot-shaped carrier housing 1 , which is pushed with its open end onto an annular collar 2 on the outer side of a countershaft housing 3 of a vehicle transmission and is fastened to the annular collar 2 with fastening elements 4 . The carrier housing 1 surrounds two brake disks 5 , 6 , which are arranged at a distance from one another and have central, internally toothed through holes 7 , with which they are axially displaceable and non-rotatably mounted on an externally toothed shaft 8 , to which the braking torque is transmitted. On both sides of the brake discs 5 , 6 there are brake pads 9 , which are arranged on circular disk-shaped pad carrier plates 10 , 11 , 12 , 13 . The rear sides of the two outer lining carrier plates 10 , 13 rest against hollow pressure rings 14 , 15 , through the interior of which a coolant is passed. The pressure ring 14 lies against the base plate 16 of the housing 1 . The back of the pressure ring 15 rests on the ring collar 2 of the countershaft housing 3 . Between the lining carrier plates 11 and 12 there is an annular housing 17 , which consists of two housing halves 18 , 19 screwed together. In the housing 17 brake cylinder 20 are inserted, the two oppositely acting brake piston in each case 21, 22 contained ten. With their outer end faces are the brake pistons 21, 22 of annular pressure plates 23, 24, which are located on both sides of the housing 17 and a brake actuation for a better distribution of the brake pistons 21 , 22 outgoing actuating forces on the lining carrier plates 11 , 12 are used.

The carrier housing 1 has on several, for example on three longitudinal sides slots 25 , in which radially outwardly extending lugs 26 of the lining carrier plates 10 to 13 are guided, which act on the lining carrier plates 10 to 13 during a braking operation braking torque on the Trägerge housing 1 transferred. The pressure rings 14 , 15 , the housing 17 and the pressure plates 23 , 24 are substantially free of torque forces, but they are also guided via lugs 27 in the slots 25 and thereby fixed in position within the carrier housing 1 . In addition to the torque support and guidance of the individual components, the slots 25 also serve to carry out the brake lines and the coolant lines.

The configuration of the housing 17 and the brake cylinders 20 arranged therein is shown in more detail in FIG. 2. The ring-shaped interior 28 of the housing 17 is flowed through by a coolant which is supplied via an inlet channel 29 and discharged via an outlet channel 30 . The coolant flows around the brake cylinder 20 , so that good cooling of the brake cylinder 20 is ensured. The brake piston 21 to be able to lock in its braking position 22, the brake cylinders are provided with a locking mechanism 20 having a locking wedge 31 which is inclined between the cylinder axis, mutually facing wedge surfaces 32, 33 of the brake piston 21, 22 is movable, so that the brake pistons 21 , 22 are supported against each other and can no longer return to their brake release position. The locking wedge 31 is fastened to a locking piston 34 , which is designed as a stepped piston and radially penetrates the cylinder wall of the brake cylinder 20 with a smaller piston step. The larger piston stage of the locking piston 34 limits the pressure chamber of a locking cylinder 35 , which is located in a cast on the brake cylinder 20 cross dome 36 . The transverse dome 36 also contains a connection bore 37 which communicates with the Gesperrezylin 35 and a connection bore 38 from which two connection bores 39 , 40 lead to the cylinder chamber 41 of the brake cylinder 20 . The connecting bores 39 , 40 run at an acute angle to one another and open into the cylinder chamber 41 at a distance of approximately 90 °. This makes it possible to arrange the brake cylinder 20 in various angular positions in the housing 17 in which the connection bores 37 , 38 are located above the locking cylinder 35 or the brake cylinder 20 , at least one connecting bore 39 or 40 opening into the apex of the cylinder chamber 41 . In this way, a uniform Bremszy cylinder version can be installed in different mounting positions in the housing 17 , as shown in Fig. 2, without the ventability of the cylinder chambers 41 and the locking cylinder 35 is impaired.

In the full-disc brake shown, six brake cylinders 20 are arranged in the housing 17 , three of which are connected to a common brake line 42 and 43 and a common control line 44 and 45 , respectively. The brake lines 42 , 43 are connected to the connection bores 38 and the control lines 44 , 45 are connected to the connection bores 37 . The dead ends of the brake lines 42 , 43 and the control lines 44 , 45 are found on the top of the housing 17 on both sides of the outlet channel 30 and are closed there with vent valves 46 .

Fig. 3 shows a brake system for actuating a full-pad disc brake according to FIGS. 1 and 2. For simplification reasons, only a single brake cylinder 20 is shown, which is supplied with pressure medium via a brake line 42 and a control line 44 . To generate the actuation pressure, the brake system shown has two independent service brake circuits I, II, each of which is fed by a separate pump 48 driven by an electric motor 47 , the output of which is connected via a check valve 49 to a pressure accumulator 50 . Overloading of the pressure accumulator 50 is prevented by a pressure relief valve 51 . From each pressure accumulator 50 , a pressure line 52 leads to the input of a two-circuit service brake valve 53 , which can be actuated with the aid of a brake pedal 54 and at whose separate outputs the two service brake circuits I, II are connected. Through the service brake valve 53 , the service brake circuits I, II can be connected to the pressure lines 52 or to a return line 55 , which leads to a container 56 . The service brake valve 53 is designed such that the pressure in the service brake circuits I, II can be controlled in proportion to the actuating force exerted on the brake pedal 54 .

In the connected to the service brake circuit II Bremslei device 42 , a parking brake valve 57 is also connected, which can be actuated via a parking brake lever 58 . By actuating the parking brake valve 57 , the brake line 42 can be separated from the service brake circuit II and connected to a parking brake circuit III or to a return line 60 connected to a container 59 . To the parking brake valve 57 which leads to the Gesperrezylinder 35 control line 44 is further connected, through a 57 Be actuation of the parking brake valve also connected to the parking brake circuit III or the return line is connectable 60th The parking brake circuit III, like the two service brake circuits I, II, is fed by a pump 65 driven by an electric motor 47 , to which a pressure accumulator 66 and a pressure relief valve 51 are connected via a check valve 49 .

The parking brake valve 57 has four switching positions 61 , 62 , 63 , 64 , which can be switched in succession. In the switching position 61 , the connection from the service brake circuit II to the brake line 42 is open and the control line 44 is connected to the return line 60 . In the switching position 62 , the brake line 42 is connected to the parking brake circuit III and the input of the service brake circuit II is closed. The control line 44 is still connected to the return line 60 . In the switching position 63 , the brake lines 42 and the control lines 44 are connected together to the parking brake circuit III. The connections of the service brake circuit II and the return line 60 are closed. In the switching position 64 , the brake lines 42 and the control line 44 are connected to the return line 60 and the connections of the service brake circuit II and the parking brake circuit III are closed.

The operation of the brake system shown in Fig. 3 is as follows:

In the brake release position shown in the drawing, the service brake valve 53 is in its basic position and the parking brake valve 57 in its switching position 61 . The brake line 42 is connected to the return line 55 and the control line 44 to the return line 60 . The brake pistons 21 , 22 and the locking piston 34 are thus in their retracted position.

If the brake pedal 54 is actuated, the brake line 42 is connected to the pressure line 52 via the operating brake valve 53 , as a result of which the pressure in the cylinder chamber 41 increases and the brake pistons 21 , 22 are acted upon. As a result, the brake pistons 21 , 22 are moved apart, moving the pad carrier plates 11 , 12 with their brake pads 9 against the brake disks 5 , 6 via the pressure plates 23 , 24 . The brake discs 5 , 6 slide here on the shaft 8 until they lie with their opposite friction surfaces on the brake pads 9 of the pad carrier plates 10 , 13 . Corresponding to the pressure increase in the brake cylinder 20 is on the brake discs 5 , 6, a friction torque for braking the shaft 8, he testifies. The pressure prevailing in the cylinder chamber 41 also strikes the small piston stage of the locking piston 34 and holds it in its release position. If the brake pedal is released, it, like the service brake valve 53 , returns to its starting position by spring force. As a result, the brake line 42 is connected again to the return line 55 , so that the pressure in the brake cylinder 20 can decrease towards the container 56 and the brake pistons 21 , 22 can return to their brake release position. The Lösebe movement of the brake pistons 21 , 22 and the pressure plates 23 , 24 can be supported by springs, not shown. Furthermore, a hydraulic clearance adjustment can be seen, which limits the release stroke of the brake pistons 21 , 22 .

To actuate the parking brake, the parking brake lever 58 is moved to the left in the drawing and the parking brake valve 57 is first brought into the switching position 62 . The brake line 42 is connected to the parking brake circuit III and the brake cylinder 20 is actuated with the pressure prevailing in the parking brake circuit III. The brake is applied in this way as for service braking, but none of the actuating force on the parking brake lever 58 is provided proportional control of the actuating pressure. The locking wedge 31 remains in its release position, since the locking cylinder 35 is not pressurized. The brake can therefore be released immediately by moving the parking brake valve back into the switching position 61 . The switching position 62 is therefore suitable for releasing the brake after a parking brake operation and also for emergency brake application of the brake in the event of failure of the service brake circuit II.

If the parking brake valve 57 is brought into the switching position 63 , in addition to the brake cylinder 20 , the locking cylinder 35 is also acted upon with the pressure in the parking brake circuit III. The locking piston 34 thereby moves the locking wedge 31 in the radial direction until it contacts the wedge surfaces 32 , 33 of the actuated brake pistons 21 , 22 . If the parking brake valve 57 is now brought into the switching position 64 and the pressure in the brake cylinder 20 and in the locking cylinder 35 is reduced via the return line 60 , the locking wedge 31 holds the brake pistons 21 , 22 in their actuating position due to its frictional engagement with the wedge surfaces 32 , 33 . The brake remains locked in this way, the braking force is maintained by the elastic deformation of the individual brake components during the pressure build-up phase. With the help of the locking wedge 31 , a mechanical locking of the brake pistons 21 , 22 is thus effected in the braking position and the actuation of the brake is maintained without a pressure remaining in the cylinder chamber 41 . If this parking brake position is canceled again, the parking brake valve 67 is moved back via the switching position 63 into the switching position 62 , in which only the cylinder chamber 41 is pressurized, while the locking cylinder 35 is connected to the return line 60 . The pressure introduced into the cylinder chamber 41 relieves the locking wedge 31 and, at the same time, acts on the locking piston 34 in the release direction, so that it returns to its rest position together with the locking wedge 31 . During a subsequent pressure relief of the cylinder chamber 41 by moving the parking brake valve 57 back into its switching position 61 , the two brake pistons 21 , 22 can therefore return to their brake release position unhindered, as a result of which the brake is relieved again.

The brake system described has the advantage that the brake moment in the parking brake position are the same size can, like the braking torque in the service brake position. The The vehicle can therefore be safely parked on steep slopes will. Through the hydraulic control of the parking brake locked can be mechanical transmission means for generation and maintaining the parking brake force. Here through the construction effort, especially for braking systems for Heavy vehicles significantly reduced.

Reference symbol list

1 carrier housing
2 ring collar
3 countershaft housing
4 fastener
5 brake disc
6 brake disc
7 hole
8 wave
9 brake pad
10 topping plate
11 topping plate
12 topping plate
13 topping plate
14 pressure ring
15 pressure ring
16 base plate
17 housing
18 housing half
19 housing half
20 brake cylinders
21 brake pistons
22 brake pistons
23 pressure plate
24 printing plate
25 slots
26 noses
27 noses
28 interior
29 inlet duct
30 outlet duct
31 locking wedge
32 wedge surface
33 wedge surface
34 locking pistons
35 locking cylinder
36 Cross Deom
37 connection bore
38 connection bore
39 connecting hole
40 connecting hole
41 cylinder chamber
42 brake line
43 brake line
44 control line
45 control line
46 breather valves
47 electric motor
48 pump
49 check valve
50 pressure accumulators
51 pressure relief valve
52 pressure line
53 Service brake valve
54 brake pedal
55 return line
56 containers
57 Parking brake valve
58 Parking brake lever
59 containers
60 return line
61 switch position
62 switch position
63 switch position
64 switch position
65 pump
66 pressure accumulator
I service brake circuit
II service brake circuit
III Service brake circuit

Claims (15)

1. Hydraulic actuating device for a friction brake, in particular for motor vehicles, with a Bremszy cylinder and at least one axially movable brake piston in the brake cylinder for pressing a friction body against a brake surface, characterized in that between the brake piston ( 21 or 22 ) and an abutment ( 22 or 21 ) a hydraulically actuated, self-locking mechanism ( 31 to 33 ) is provided, through which the brake piston ( 21 or 22 ) in the brake release direction on the abutment ( 22 or 21 ) can be supported. 2. Brake actuating device according to claim 1, characterized in that the locking mechanism ( 31 to 33 ) has a locking wedge ( 31 ) movable transversely to the longitudinal axis of the brake cylinder ( 20 ) and having a wedge surface ( 32 or 33 ) on the rear side of the brake piston ( 21 or 22 ) and / or the abutment ( 22 or 21 ) cooperates. 3. Brake actuating device according to one of claims 1 or 2, characterized in that the abutment ( 22 or 21 ) is formed by a second brake piston ( 21 or 22 ) for actuating a second friction body ( 9 ). 4. Brake actuating device according to one of the preceding claims, characterized in that for actuating the locking wedge ( 31 ) a locking cylinder ( 35 ) with a locking piston ( 34 ) is provided and that the locking cylinder ( 35 ) is connected radially to the brake cylinder ( 20 ) . 5. Brake actuating device according to claim 4, characterized in that the locking piston ( 34 ) is designed as a stepped piston and projects with its smaller piston step into the cylinder chamber ( 41 ) of the brake cylinder ( 20 ) and is connected there with the locking wedge ( 31 ). 6. Brake actuating device according to one of the preceding claims, characterized in that the locking wedge ( 31 ) between its opposite wedge surfaces is limited by part cylinder surfaces, the curvature of which corresponds to the curvature of the cylinder bore of the brake cylinder ( 20 ). 7. Brake actuating device according to claim 6, characterized in that the partial cylinder surfaces in the region of connection bores ( 39 , 40 ) which open into the brake cylinder ( 20 ) have recesses. 8. Brake actuating device for a full-lining brake according to one of the preceding claims, characterized in that in an annular housing ( 17 ) distributed over the circumference several of the brake cylinder ( 20 ) and locking cylinder ( 35 ) existing, uniform actuating units are arranged, which are via brake lines ( 42 ) and control lines ( 44 ) are interconnected. 9. Brake actuating device according to claim 8, characterized in that the actuating units are arranged so that their locking cylinders ( 35 ) are directed upwards with respect to a Hori zontalplane and extend in the circumferential direction of the housing ( 17 ). 10. Brake actuating device according to one of claims 8 or 9, characterized in that the brake cylinder ( 20 ) have two connection bores ( 39 , 40 ) which run at an acute angle to one another and which lie in a common connection channel located above the cylinder bore ( 41 ) ( 38 ) open. 11. Brake actuating device according to one of claims 8 to 10, characterized in that the interior ( 28 ) of the ring-shaped housing ( 17 ) can be flowed through by a coolant. 12. Brake actuating device according to one of the preceding claims, characterized in that for actuating one or more brake cylinders ( 20 ) a service brake valve ( 53 ) and for actuating one or more locking cylinders ( 35 ) a parking brake valve ( 57 ) is provided, and in that the brake valves ( 53 , 57 ) brake cylinder ( 20 ) and Spreizzylin ( 35 ) with an unpressurized container ( 56 , 59 ) or with a pressure source ( 48 , 50 ; 65 , 66 ) can be connected. 13. Brake actuating device according to claim 12, characterized in that the parking brake valve ( 57 ) between the output of the service brake valve ( 53 ) and the brake cylinder or cylinders ( 20 ) is connected. 14. Brake actuating device according to claim 13, characterized in that the parking brake valve ( 57 ) or the brake cylinder ( 20 ) in a first switching position ( 61 ) with the output of the service brake valve ( 53 ), in a second and third switching position ( 62 , 63 ) with a pressure medium source ( 48 , 50 ; 65 , 66 ) connected to the parking brake valve ( 57 ) and in a fourth switching position ( 64 ) with a return line ( 60 ) and the locking cylinder (s) ( 35 ) in the first, second and fourth switching position ( 61 , 62 , 64 ) with the return line ( 60 ) and in the third switching position ( 63 ) with the pressure medium source ( 48 , 50 ; 65 , 66 ). 15. Brake actuating device according to one of claims 12 to 14, characterized in that the service brake valve ( 53 ) and the parking brake valve ( 57 ) to independent pressure medium sources ( 48 , 50 ; 65 , 66 ) are connected.