Abstract:
The invention relates to a brake mechanism ( 1 ) for agricultural utility vehicles. In the case of the brake mechanism ( 1 ), during a brake application an additional quantity of oil is supplied to a brake chamber ( 150 ) via an inlet manifold ( 180 ), which is fluidically connected to an oil chamber ( 130 ). The service brake is formed so that, when the service brake is operated, a first control element ( 120 ) is moved towards the brake elements ( 140, 141 ) in such a way that a brake chamber ( 150 ) is fluidically connected to the inlet manifold ( 180 ) and thus ensures an additional oil supply from the oil chamber ( 130 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a brake mechanism for a vehicle, in particular an agricultural utility vehicle. 
     2. Description of Related Art 
     In the case of agricultural utility vehicles, brake mechanisms are used which can comprise a service brake and a parking brake. These service brakes and parking brakes must, in operation, fulfil high performance requirements due to the heavy weight of the utility vehicles and the towing loads. The brake mechanisms, in the case of agricultural utility vehicles, are also provided on the output shaft in the drive train. 
     The output shaft here has a substantially higher rotational speed in comparison to a wheel speed. Therefore brake disks of the brake mechanism, which are arranged on the output shaft, and stationary brake disks, which are arranged on a rotationally-fixed housing of the brake mechanism, have a high rotational speed difference. Thus during a brake application, undesirably high heat can develop in the brake mechanism due to the friction between the brake disks. 
     This heat development can be counteracted for example with an annular piston brake, such as for example a cardan brake, integrated into a transmission, by cooling the brake disks. The brake disks are arranged in the brake mechanism in such a way that they are brought into contact with heat-dissipating oil. At the same time the oil quantity necessary for cooling the brake disks may, depending on the arising heat development, be controlled by a pump unit, such as for example a transmission pump. If the rotational speed of the output shaft is high, a larger quantity of oil for cooling the brake mechanism must be supplied by the transmission pump. This larger quantity of oil can only be made available by greater power of the transmission pump. However this increased power of the transmission pump reduces the utility vehicle power that is available overall in the utility vehicle. Therefore the utility vehicle power is affected inter alia by the power required by the transmission pump. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is therefore to provide a brake mechanism wherein better cooling of the brake mechanism with less utility vehicle power loss can be guaranteed. 
     According to the invention there is provided a brake mechanism with a rotationally-fixed housing, an output shaft rotatably arranged in the housing and brake elements for braking the output shaft, wherein the housing comprises a brake chamber provided with a control element and wherein said brake chamber is fluidically connected to a brake element chamber, the brake elements are arranged in the brake element chamber so that during a braking application oil is supplied to the brake chamber from an oil chamber arranged outside the housing, said housing provided with a recess which extends into an oil free part of the oil chamber. 
     Preferably, the recess is arranged above an oil bath formed inside the oil chamber. 
     Preferably the brake mechanism has an adjustable first control element which is formed and arranged so that during a brake application the brake chamber is fluidically connected to the oil chamber and the brake chamber is separate from the oil chamber. 
     More preferably the first control element is formed so that it is adjustable during a brake application by means of an actuating pressure so that it comes into contact with the brake elements and moves the brake elements into frictional contact with one another and wherein the brake chamber is fluidically connected to the oil chamber. 
     Preferably the brake chamber and the oil chamber are connected by an inlet manifold. 
     More preferably the oil chamber is permanently fluidly connected via a connecting element to the brake chamber. 
     More preferably the connecting element is formed as a notch on the first and/or second control element. 
     Preferably still the connecting element is formed as a hole connecting the inlet manifold and the brake chamber in the first and/or second control element. 
     The advantages gained by the invention are particularly that, additionally to the quantity of oil made available by the transmission pump, a further quantity of oil can be supplied to the brake mechanism from an oil chamber. Thus an altogether larger quantity of oil is available to the inventive embodiment for cooling the brake elements than in the case of the embodiment wherein the quantity of oil is supplied by the transmission pump alone. Thus undesirable heat development in the brake mechanism can also be better dissipated through the larger quantity of oil available. In fact the quantity of oil supplied from the oil chamber can exceed the quantity of oil supplied by the transmission pump, so that even a smaller, lower-powered transmission pump is sufficient. Due to the use of a smaller, lower-powered transmission pump the utility vehicle power losses caused by the transmission pump are also reduced. 
     A further advantage of the invention is that the additional quantity of oil supplied from the oil chamber can be controlled. Thus it can be guaranteed that, during a brake application, a larger quantity of oil is found inside a brake element chamber than in an operating condition in which the brake is not operated. Therefore the resistance caused by the oil in the brake element chamber against rotation of the brake disks, which partially extend into the oil bath of the brake element chamber, is also reduced. Thus the power losses (wheel drive losses) caused by this are reduced. 
     A further advantageous embodiment of the invention consists in the fact that a brake chamber is separated from an inlet manifold, which is connected to the oil chamber, by an adjustable first control element already present in the brake mechanism. Thus the brake mechanism must only be adapted so that for example in the housing of the brake mechanism an inlet opening, connecting the inlet manifold to the brake chamber, is provided. This inlet opening can be fabricated cost-effectively, for example when the housing is cast. 
     A further advantageous embodiment of the invention consists in the fact that for example a connecting element can be formed between the brake chamber and the oil chamber so that a constant oil supply to a brake chamber of the brake mechanism can be guaranteed. Thus it can be guaranteed, for example in emergency operation of the vehicle, during which a braking action is to take place via the parking brake alone, that the brake elements are sufficiently cooled. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Details of the invention are described in more detail on the basis of the drawings in which there are shown: 
         FIG. 1  a brake mechanism, wherein no brake applications takes place, 
         FIG. 2  a brake mechanism, wherein a brake application takes place. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a brake mechanism  1 , wherein no brake operation takes place. The brake mechanism  1  comprises a stationary, non-rotating housing  100 , which is arranged with one end in an oil chamber  130 . The oil chamber  130  in this case is filled with oil only to a predetermined level. Additionally the oil chamber  130  is arranged for example in a gear unit of the utility vehicle, not illustrated in  FIG. 1 . Only one part of the housing  100  is in contact with the oil bath in the oil chamber  130 . Moreover the housing  100  comprises a recess  101  which extends into the oil chamber  130 . This recess  101  is arranged in an oil free part of the chamber  130  above the oil line of the oil bath formed inside the oil chamber  130 . 
     A control area  160  and a brake element chamber  142  are formed inside the housing  100 . Moreover a rotatable output shaft  110 , which passes through the control area  160  and the brake element chamber  142 , is arranged inside the housing  100 . Brake elements  140 ,  141 , which in this exemplary embodiment are formed as brake disks  140 ,  141 , are arranged in the brake element chamber  142 . At the same time the brake disks  140 ,  141  are fastened in each case alternating on the rotationally-fixed housing  100  and the output shaft  110 . Moreover one end of the brake elements  140 ,  141  extends into an oil sump located in the brake element chamber  142 . 
     A first and second control element  120 ,  122  are arranged in the control area  160 . The first and second control element  120 ,  122 , are each formed cylindrically, having a flange at one end in each case. Additionally a first spring element  124 , which is coupled with a front side of the flange end of the second control element  122  and the housing  100 , is arranged in the control area  160 . However the flange end of the first control element  121  points with its front side towards the brake element chamber  142 . A second spring element  170  is arranged between the first and second control element  120 ,  121 . This second spring element  170  is formed as a tension spring for example. 
     In the case illustrated in  FIG. 1  the first control element  120  is in contact with the second control element  122 . The front side of the end of the first control element  120  turned away from the brake element chamber  142  touches the surface, pointing towards the first control element  120 , of the flange end of the second control element  122 . Moreover in this illustrated case, the front side of the flange end of the first control element  120  is not in contact with the brake elements  140 ,  141 . 
     A first control chamber  121  is formed between the first control element  120  and the housing  100 . Furthermore a brake chamber  150 , which is fluidically connected to the brake element chamber  142 , is formed between the first control element  120  and the second control element  122 . Moreover a second control chamber  123  is formed between the second control element  122 , the housing  100  and an annular element  125 . The annular element  125  in this case is arranged on the housing and fixed against movement. 
     At the same time the first control chamber  121  forms with the first control element  120  part of a service brake. The second control chamber  123  forms with the second control element  122  and the first spring element  124  part of the parking brake. 
     Between a housing of the—not illustrated—gear unit and the housing  100  of the brake mechanism, an inlet manifold  180  is formed in the region of the oil bath. In addition the housing  100  has an inlet opening  190 , via which the brake chamber  150  in this case can be fluidically connected to the inlet manifold  180 . The brake chamber  150  in this case is fluidically connected to the oil chamber  130 . The inlet opening  190  is located on the part of the housing  100 , which extends into the oil bath, that is to say below the oil level. In a condition of the service brake in which no braking action is carried out by this, the inlet opening  190  is closed by a peripheral face of the first control element  120 . Therefore no oil can flow via the inlet manifold  180  to the brake chamber  150  in this position of the first control element  120 . 
     Axial movement of the first and/or second control element  120 ,  122  can be controlled in each case by means of the first and/or second control chamber  121 ,  123 . In the case illustrated in  FIG. 1  the actuating pressure prevailing in the second control chamber  123  is increased. Thus force is exerted on the second control element  122  towards the first spring element  124 . Therefore the second control element  122  moves in this direction, as a result of which the first spring element  124  is compressed together. Moreover the actuating pressure prevailing in the first control chamber  121  is not increased in this case. 
     Due to the coupling of the first control element  120  with the second control element  122  via the second spring element  170 , the first control element  120  is moved in the same direction as the second control element  121 . In the case illustrated in  FIG. 1  the inlet opening is thus closed by the first or second control element  120 ,  122 . Therefore fluid present in the inlet manifold  180  cannot flow into the brake chamber  150 . 
     The position of the control elements  120 ,  122  illustrated in  FIG. 1  corresponds in this case to a position of the brake mechanism in which no braking action is to be exerted on the output shaft  110 . 
       FIG. 2  shows a brake mechanism wherein a braking action is effected by the service brake. During a desired braking action by the service brake, the first control element  120  moves towards the brake elements  140 ,  141  due to the increase in pressure of the first control chamber  121 . This movement takes place so long as the first control element  120  is in contact with the brake elements  141 ,  140  and thus a braking action takes place on the output shaft  110 . In this case the actuating pressure prevailing in the second control chamber  123  is increased, so that the second control element  122  does not move. 
     As a result of the movement of the first control element  120  towards the brake elements  140 ,  141 , the inlet opening is no longer completely closed by the peripheral face of the first control element  120 . Thus fluidic connection between the inlet manifold  180  and the brake chamber  150  is facilitated. Therefore oil can flow from the oil chamber  130  via the inlet manifold  180  to the brake chamber  150 . Additionally the oil located in the brake chamber  150  continues to flow into the brake element chamber  142  and thus comes into contact with the brake elements  140 ,  141 , as a result of which the brake elements  140 ,  141  are cooled. The oil in the brake element chamber  142  is ejected by rotation of the output shaft  110  and the second brake elements  140  arranged thereon via the recess  101  arranged in the housing  100 . 
     This heated oil ejected from the brake mechanism  1  can be subsequently cooled through components, which are not illustrated in  FIG. 2  and are arranged in an oil circuit. 
     After a brake application by the service brake, the actuating pressure prevailing in the first control chamber  121  is reduced. Consequently the first control element  120 , due to the coupling with the second spring element  170 , is moved towards the second control element  122 . 
     During a braking action, not illustrated in  FIGS. 1 and 2 , by the parking brake, the actuating pressure prevailing in the second control chamber  123  is reduced as shown in  FIG. 1 . Therefore the second control element  122 , due to the spring force exerted by the first spring element  124  on the flange end of the second control element  122 , is moved towards the brake elements  140 ,  141 . Since the second control element  122  is in contact with the first control element  121 , the first control element  121  is also moved towards the brake elements  140 ,  141  accordingly. The control elements  120 ,  122  are moved so far until the first control element  121  is in contact with the brake elements  140 ,  141 . In this case fluidic connection of the brake chamber  150  to the inlet manifold  180  is prevented by the control elements  120 ,  122 . 
     Alternatively to the embodiments illustrated in  FIGS. 1 and 2 , independently of the position of the control elements  120 ,  122 , a continuous oil supply from the inlet manifold  180  to the brake chamber  150  can be regulated. This could take place for example via a notch arranged in the first and/or second control element  120 . Alternatively the quantity of oil that is supplied can be controlled via a hole connecting the inlet manifold  180  and the brake chamber  150 . The hole in this case could be formed in the first and/or second control element  120 ,  121 .