Abstract:
A hydraulic motorcycle braking system is disclosed. In the hydraulic motorcycle braking system a pump suction valve, which is situated in a braking circuit that does not contain an isolating valve or a change-over valve, has a higher opening pressure than a pump suction valve which is situated in a braking circuit provided with an isolating valve and a change-over valve. Accordingly, pressure oscillations initiated during the start-up of the pump cannot have a retroactive effect or only have a slight retroactive effect on the actuated brake master cylinder.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2007/054586, filed May 11, 2007, which claims priority to German Patent Application No. DE102006023341.7, filed May 17, 2006 and German Patent Application No. DE102006045038.8, filed Sep. 23, 2006, the contents of such applications being incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a motorcycle brake system. 
         [0004]    2. Description of the Related Art 
         [0005]    EP 1 277 635 A2 has already disclosed a motorcycle brake system of said type. The brake system has a hydraulically actuable front wheel brake circuit and rear wheel brake circuit, with each individual brake circuit being connected either to a foot-actuated or hand-actuated master brake cylinder. For brake slip regulation, electromagnetically activatable inlet and outlet valves are arranged in the front wheel brake circuit and rear wheel brake circuit, with a pump for building up pressure in the two brake circuits. The rear wheel brake circuit has an additional valve arrangement which, in the event of a manual actuation of the front wheel brake circuit, permits a simultaneous build-up of pressure at the rear wheel brake by means of the pump without it being necessary for the master brake cylinder of the rear wheel brake circuit to be actuated. 
         [0006]    A first pressure sensor is arranged at the front wheel brake circuit in order to detect the manual actuation of the front wheel brake circuit and in order to be able to activate the pump to build up an autonomous brake pressure in the rear wheel brake circuit. 
         [0007]    Depending on the reliable detection of the master brake cylinder pressure in the front wheel brake circuit, the pump can then be electrically activated, and a regulated brake pressure can be built up in the rear wheel brake. 
         [0008]    As the pump starts up, however, there is the problem that pressure fluctuations are initiated which feed back to the manually actuated master brake cylinder, and are perceptible in the hand brake lever, which is displeasing. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to improve a motorcycle brake system of the known type in such a way that the pressure fluctuations which are initiated as the pump starts up cannot feed back, or can feed back only slightly, to the manually actuated master brake cylinder. 
         [0010]    According to one aspect of the invention, in the braking system a pump suction valve, which is situated in a braking circuit that does not contain an isolating valve or a change-over valve, has a higher opening pressure than a pump suction valve which is situated in a braking circuit provided with an isolating valve and a change-over valve. 
         [0011]    These and other aspects of the invention are illustrated in detail by way of the embodiments and are described with respect to the embodiments in the following, making reference to the Figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    The invention is best understood from the following detailed description when read in connection with the accompanying drawing. Included in the drawing are the following figures: 
           [0013]      FIG. 1  shows the hydraulic circuit diagram for a motorcycle brake system which is improved with respect to the prior art and whose front wheel brake circuit, during autonomous operation of the rear wheel brake as a result of an increase in the opening pressure at the pump suction valve, is not subjected, or is subjected only slightly, to feedback from the pump to the hand brake lever, 
           [0014]      FIG. 2  shows a hydraulic circuit diagram for a motorcycle brake system in an embodiment which differs from  FIG. 1  and whose front wheel brake circuit is provided with the cut-off valve and switching valve known from  FIG. 1 , such that during autonomous operation of the front wheel brake circuit, a feedback from the pump to the master brake cylinder which is provided with the hand brake lever is prevented, 
           [0015]      FIG. 3  shows the hydraulic circuit diagram according to  FIG. 2 , expanded by a second front wheel brake or alternatively by a front wheel brake with a plurality of wheel brake cylinders which can be actuated independently of one another and which, by means of a division of the brake line which is connected to the front wheel brake circuit between two front wheel brakes or between the wheel brake cylinders which can be actuated independently of one another, are connected to the hand-actuable master brake cylinder, 
           [0016]      FIG. 4  shows the hydraulic circuit diagram according to  FIG. 3 , additionally with a line connection between the brake line of the rear wheel brake circuit and the pump suction path in which a check valve is arranged. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]      FIG. 1  shows the hydraulic circuit diagram of an improved, new motorcycle brake system in schematic form. The brake system is composed of a hydraulically actuable front wheel brake circuit  4  and rear wheel brake circuit  10 , having in each case one master brake cylinder  7  which is connected to the front wheel brake circuit  4  and can be actuated proportionally by hand force, and having a master brake cylinder  13 , which can be actuated in proportion to a foot force, on the rear wheel brake  14 . 
         [0018]    For brake slip regulation, electromagnetically actuable inlet and outlet valves  6 ,  12  are arranged in both the front wheel brake circuit  4  and in the rear wheel brake circuit  10 , wherein in each case the inlet valve  6  which is open in the home position is arranged in the brake line  18  of the front wheel brake circuit  4  or of the rear wheel brake circuit  10 , which brake line  18  connects the respectively associated master brake cylinder  7 ,  13  to the front wheel brake  5  or the rear wheel brake  14 . The outlet valve  12  which is closed in the home position is arranged in each case in a return line  15  of each brake circuit, which return line  15  connects the front wheel brake  5  or rear wheel brake  14  in each case to a low pressure accumulator  16  and to the suction side of a pump  9  which is divided into two circuits and which operates according to the feedback principle. The pump  9  is therefore connected via noise damping chambers  17 , which are arranged in the two brake circuits, to the brake lines  18  upstream of the inlet valves  6 , so as to ensure that the brake fluid volume which is respectively let out from the front wheel brake  5  or rear wheel brake  14  is fed back according to demand. 
         [0019]    The rear wheel brake circuit  10  has, in addition to the illustrated features of the front wheel brake circuit  4 , an electromagnetically actuable cut-off valve  19  which is arranged in the brake line  18  between the master brake cylinder  13  and the inlet valve  6 , which cut-off valve  19  is open in its home position. Furthermore, between the cut-off valve  19  and the master brake cylinder  13 , a suction path  21 , which leads via an electric switching valve  20 , to the pump  9  is connected to the brake line  18  of the rear wheel brake circuit  10 , as a result of which the pump part which acts in the rear wheel brake circuit  10  can, in the event of the electrical excitation of the switching valve  20 , extract pressure medium from the master brake cylinder  13  and supply said pressure medium to the rear wheel brake  14  for an autonomous build-up of pressure in the rear wheel brake  14 , while the cut-off valve  19  remains in its electrically excited blocking position in order to prevent a feedback into the master brake cylinder  13 . 
         [0020]    To detect the master brake cylinder pressure supplied to the front wheel brake circuit  4 , a first pressure sensor  1  is situated upstream of the inlet valve  6  on the brake line  18  of the front wheel brake circuit  4 . To detect the wheel brake pressure in the rear wheel brake circuit  10 , a second pressure sensor  2  is connected to the rear wheel brake circuit downstream of the inlet valve  6 , and a third pressure sensor upstream of the cut-off valve  19 , as a result of which the actuation of the master brake cylinder  13  can also be reliably detected. 
         [0021]    By means of the inlet valves  6 , it is possible, in the two-circuit brake system, for the brake pressure generated in the brake lines  18  to be limited at all times. The build-up of brake pressure in the wheel brakes takes place by means of the outlet valves  12 , which can be opened under the action of an electromagnet, in the direction of the two low-pressure accumulators  16 . The details in this regard can be gathered from the functional description regarding brake slip regulation in one of the following sections of the description. 
         [0022]    The master brake cylinder pressure detected by means of the first pressure sensor  1  in the front wheel brake circuit  4  forms the reference variable for the electric activation of the pump  9  which acts in the rear wheel brake circuit  10  and which, in interaction with the inlet and outlet valves  6 ,  12 , the cut-off valve  19  and switching valve  20 , brings about an electrohydraulic build-up of brake pressure in the rear wheel brake circuit  10  according to an electronic brake force distribution characteristic curve, which is stored in the control unit  8 , if only the master brake cylinder  7  which is connected to the front wheel brake circuit  4  is actuated. 
         [0023]    To evaluate the pressure sensor signals, a logic circuit is provided in the electronic control unit  8 , in which logic circuit an autonomous hydraulic pressure in the rear wheel brake circuit  10  is generated by means of the electrically actuable pump  9  as a function of the result of the evaluation of the pressure sensor signals. 
         [0024]    The symbolically illustrated control unit  8  forms an integral part of a brake unit  11  which is preferably plugged, so as to make electrical contact, onto the pressure sensors which are integrated in the brake unit  11  and onto the inlet and outlet valves  6 ,  11  which are integrated therein. The brake unit  11  may therefore, on account of the particularly compact design, be fastened to a motorcycle frame in the vicinity of a battery. 
         [0025]    It is basically the case that: 
         [0026]    1. A locking tendency of the front wheel or rear wheel is reliably detected by means of wheel speed sensors (not shown) and the evaluation of their signals in the control unit. The inlet valve  6  which is arranged in the front wheel brake circuit  4  or in the rear wheel brake circuit  10  is closed electromagnetically by means of the control unit  8  in order to prevent a further build-up of pressure in the front wheel brake circuit  4  or rear wheel brake circuit  10 . 
         [0027]    2. If, to reduce the locking tendency, a further dissipation of pressure in the front wheel brake circuit  4  or rear wheel brake circuit  10  is necessary, this is obtained by opening the outlet valve  12  which can be connected in each case to the low-pressure accumulator  16  and which is normally closed in the currentless state. The outlet valve  12  is closed once the wheel acceleration rises beyond a certain value again. In the pressure dissipation phase, the corresponding inlet valve  6  remains closed, such that the master brake cylinder pressure which is generated in the front wheel brake circuit  4  or rear wheel brake circuit  10  respectively cannot propagate to the front wheel brake circuit or rear wheel brake circuit  10  respectively. 
         [0028]    3. If the determined slip values again permit a pressure build-up in the front wheel brake circuit  4  or rear wheel brake circuit  10 , the inlet valve  6  is opened in a time-limited fashion corresponding to the demand of the slip regulator which is integrated in the control unit  8 . The hydraulic volume required for the build-up of pressure is provided by the pump  9 . 
         [0029]    Outside the brake slip regulation, on account of the hydraulic circuit concept, in the event of an actuation (in proportion to a foot force) of the master brake cylinder  13  which is connected to the rear wheel brake circuit  10 , only the rear wheel brake  14  is pressurized proportionally in terms of force, that is to say the front wheel brake circuit  4  remains unpressurized until an actuation (in proportion to a hand force) of the master brake cylinder  7  which is connected to the front wheel brake circuit  4 . 
         [0030]    A peculiarity of the proposed motorcycle brake system as per  FIG. 1  is that, in the event of a force-proportional actuation of the front wheel brake circuit  4 , the rear wheel brake  14  is autonomously co-braked as a result of a suitable pump activation. For this purpose, the pump  9  extracts pressure medium from the master brake cylinder  13  via the electrically opened switching valve  20 , and feeds said pressure medium to the rear wheel brake  14 . Here, the cut-off valve  19  remains, electrically actuated, in the closed position, thereby ensuring that the pump pressure does not escape into the master brake cylinder  13 . 
         [0031]    Secondly, on account of the two-circuit design of the pump  9  and the associated simultaneous build-up of pressure in the two brake circuits, a feedback of the pump pressure to the brake circuit which has the hand-actuated master brake cylinder  7  is undesirable and must therefore be prevented in the event of an autonomous and therefore externally-activatable build-up of pressure in the non-manually-actuated brake circuit, for which reason, according to aspects of the invention, as per  FIGS. 1-4 , a valve circuit is proposed which prevents a feedback of the pump pressure to the manually actuated master brake cylinder. 
         [0032]    The pump  9  of the improved motorcycle brake system according to  FIG. 1  therefore has, for each brake circuit, a valve circuit with different suction valves  24 ,  25 , with the suction valve  25  which is arranged in the exclusively manually-actuable brake circuit (front wheel brake circuit  4 ) having a significantly higher opening pressure (approx. 1.2 bar) than the suction valve  24  which is arranged in the autonomously actuable brake circuit (rear wheel brake circuit  10 ) and whose opening pressure is preferably approximately 0.2 bar. It is hereby ensured that, in the event of an autonomous build-up of pressure, which is triggered by means of the pump  9 , in the non-manually-actuated rear wheel brake circuit  10 , a feedback of the pump pressure to the manually-actuated master brake cylinder  7 , which is connected to the front wheel brake circuit  4 , is simultaneously considerably reduced. 
         [0033]    The hydraulic circuit according to  FIG. 2  shows a modification, according to aspects of the invention, of the circuit arrangement according to  FIG. 1 , with the rear wheel brake circuit arrangement known from  FIG. 1  having been transferred, with regard to the cut-off valve  19  and switching valve  20  and also with regard to the pressure holding valve  28 , to the front wheel brake circuit  4 . Accordingly, the two pump suction valves  24 ,  25  in the two brake circuits have also been exchanged. The pump suction valve  25  which is provided with the higher opening pressure is therefore situated in the rear wheel brake circuit  10 , as a result of which, in autonomous brake system operation, the feedback of the pump pressure to the foot-actuated master brake cylinder  13  is minimized. Furthermore, in  FIG. 2 , in contrast to  FIG. 1 , the pressure retaining valve  28  has now been removed from the rear wheel brake circuit and has been arranged for this purpose at the outlet side on the low-pressure accumulator  16  of the front wheel brake circuit  4 , which contributes to the secondary circuit ventilation in the rear wheel brake circuit  10  being facilitated. Specifically, in the rear wheel brake circuit  10 , the low-pressure accumulator  16  is connected directly to a branch of the return line  15 , while the low-pressure accumulator  16  which is arranged in the front wheel brake circuit  4  is advantageously rinsed in the direction of the pressure holding valve  28  via the return line  15 . 
         [0034]    Autonomous operation of the motorcycle brake system according to  FIG. 2  accordingly takes place by means of the actuation (in proportion to a foot force) of the master brake cylinder  13  which is connected to the rear wheel brake circuit  10 , as a result of which, according to the known schematic diagram (compare  FIG. 1 ), the cut-off valve  19  and switching valve  20  which are arranged in the front wheel brake circuit  4  now assume the electromagnetically excited switched position (not shown) in which the pump circuit which is connected to the front wheel brake circuit  4  is connected at the suction side to the master brake cylinder  4 , but is separated at the pressure side from the master brake cylinder  4 , while the pump circuit which is connected to the rear wheel brake circuit  10 , as a result of the increased opening pressure of the suction valve  25 , minimizes the pump feedback to the master brake cylinder  13 . Moreover, since the master brake cylinder  13  in  FIG. 2  is actuated by means of a brake pedal in proportion to a foot force, as a result of the selected brake circuit distribution, any pump feedback to the master brake cylinder  13  is barely perceptible, or not perceptible at all, to the rider. 
         [0035]    The hydraulic circuit according to  FIG. 3  shows an expansion, according to aspects of the invention, of the circuit arrangement according to  FIG. 2 , wherein in the embodiment, according to aspects of the invention, as per  FIG. 3 , the front wheel brake  5  has either two brake calipers which are functionally separate from one another, or a multi-piston brake whose brake pistons are connected to the front wheel brake circuit  4  independently of one another by means of a two-part brake line  18 . In  FIG. 3 , therefore, the autonomously regulable front wheel brake  4  known from  FIG. 2  is expanded in the direction of the symbolically illustrated second front wheel brake  5  by a line branch in which, for brake slip regulation, an inlet valve  6  is arranged upstream of the second front wheel brake  5  and an outlet valve  12  of the already-specified type is arranged downstream of the second wheel brake  5  in a further return line  15 . The line branch is branched off at the brake line  18  of the front wheel brake circuit  4  upstream of the cut-off valve  19  and switching valve  20 , such that the symbolically illustrated second front wheel brake  5  cannot be autonomously regulated but rather can only be manually actuated. This has the advantage that, during autonomous brake pressure regulation in the first front wheel brake  5 , a comfortable braking intervention into the front wheel brake circuit  4  is possible since a brake pressure may be built up, unhindered, in the symbolically illustrated second front wheel brake  5 . 
         [0036]    In the present exemplary embodiment according to  FIG. 3 , therefore, one of the two front wheel brakes  5  can be actuated only manually by means of the master brake cylinder  7 , such that a comfortable brake actuation sensation is perceptible at the brake lever of the master brake cylinder  7  at all times. 
         [0037]    In  FIG. 3 , the design of the rear wheel brake circuit  10  corresponds, in terms of all the substantial elements, to the illustration of the rear wheel brake circuit  10  according to  FIG. 2 . 
         [0038]    As depicted by way of example in  FIG. 3 , the rear wheel brake  14  may also be designed as a multi-piston brake, which pistons are all connected by means of the brake line  18  of the rear wheel brake circuit  10  to the second master brake cylinder  13 . 
         [0039]    As a further expedient distinguishing feature with respect to  FIG. 1 , the circuit arrangements according to  FIGS. 2 ,  3 ,  4  have a pump  9  whose pump suction valve  24  which is arranged in the front wheel brake circuit  4  has a significantly lower opening pressure (approx. 0.2 bar) than the further pump suction valve  25  (approx. 1.2 bar) which is arranged in the rear wheel brake circuit  10 , as a result of which a so-called idle pulsation of the pump  9  in the rear wheel brake circuit  4  in the direction of the second master brake cylinder  7  is advantageously prevented, as a result of which the foot brake lever of said second master brake cylinder can be actuated without feedback. 
         [0040]    The hydraulic circuit according to  FIG. 4  differs from the circuit arrangement according to  FIG. 3  substantially by two further additional features, wherein in addition: 
         [0041]    1. A line which is provided with a check valve  26  connects the brake line  18  of the rear wheel brake circuit  10  to the pump suction path  3  in the rear wheel brake circuit  10 , 
         [0042]    2. The two low-pressure accumulators  16  are provided with pressure retaining valves  17  which have an identical opening pressure (approx. 0.8 bar). 
         [0043]    In contrast to  FIG. 1 , in the circuit diagrams according to  FIGS. 2 to 4 , the front wheel brake circuit can in each case be autonomously regulated as a function of the manual actuation of the rear wheel brake circuit, with a pressure sensor  2  being arranged both at the rear wheel brake  14  and also at the front wheel brake in order to precisely detect the brake pressure prevailing in each case at the rear wheel brake  14  and also at the front wheel brake, in particular for brake slip regulation in the two brake circuits. 
         [0044]    Where no explanation has thus far been given regarding all the further details which can be seen from  FIGS. 2 to 4 , said details correspond functionally and in terms of design to the discussed circuit diagram according to  FIG. 1 , with all the figures having the same reference symbols for identical elements. 
         [0045]    In summary, it can therefore be stated for all the exemplary embodiments according to  FIGS. 1-4  that, according to aspects of the invention, in that brake circuit which does not have the cut-off valve  19  and switching valve  20 , the pump suction valve  25  has a higher opening pressure than the pump suction valve  24  which is arranged in that brake circuit which has the cut-off valve  19  and switching valve  20 . 
         [0046]    In this way, during autonomous operation of the motorcycle brake system, a pulsating feedback from the pump  9  to the hand-actuated or foot-actuated master brake cylinder  7 ;  13  is prevented in that brake circuit which does not have a cut-off valve  19  and switching valve  20 . 
         [0047]    As a result, corresponding to the exemplary embodiment according to  FIG. 1 , in the front wheel brake circuit  4  which does not have the cut-off valve  19  and switching valve  20 , the pump suction valve  25  has a higher opening pressure than the pump suction valve  24  which is arranged in the rear wheel brake circuit  10  and which has the cut-off valve  19  and switching valve  20 . 
         [0048]    Alternatively,  FIG. 2  shows an exemplary embodiment in which, in the rear wheel brake circuit  10  which does not have the cut-off valve  19  and switching valve  20 , the pump suction valve  25  has a higher opening pressure than the pump suction valve  24  which is arranged in the front wheel brake circuit  4  which is provided with the cut-off valve  19  and switching valve  20 . 
         [0049]    In an expansion of  FIG. 2 ,  FIG. 3  shows that that brake circuit (front wheel brake circuit  4 ) which has the cut-off valve  19  and switching valve  20  has connected to it, upstream of the cut-off valve  19  and switching valve  20 , a further wheel brake (front wheel brake  5 ) or a separately actuable brake piston, as a result of which a brake lever sensation which is desired for a conventional brake actuation is ensured at the depicted brake lever by means of the master brake cylinder  7  which is connected to the front wheel brake circuit  4  (as a result of the volume uptake of the further wheel brake or brake piston). 
         [0050]      FIG. 4  finally shows, on account of the arrangement of a pressure retaining valve  28  at the outlet of the low-pressure accumulator  16 , an expedient measure for evacuating the secondary circuit, for which purpose a check valve  26 , which opens under the action of an electromagnet, is connected to the brake line of the rear wheel brake circuit upstream of the inlet valve  6 , which check valve  26  can be connected to the suction side of the pump  9  downstream of the pressure retaining valve  28 . 
         [0051]    With regard to the design of the pump  9 , it should be noted for all exemplary embodiments that the difference in the opening pressures of the two pump suction valves  24 ,  25  is between 0.5 and 1.5 bar, preferably 1 bar. The opening pressure of the pump suction valve  24  which is arranged in that brake circuit which has the cut-off valve  19  and switching valve  20  is between 0.1 and 0.4 bar, preferably 0.2 bar, in order to obtain as high a delivery capacity as possible. In contrast, the opening pressure of the pump suction valve  25  which is arranged in that brake circuit which does not have the cut-off valve  19  and switching valve  20  is between 0.6 and 1.6 bar, preferably 1.2 bar, as a result of which, on account of the reduction of the pump suction behavior, pressure pulsations are not perceptible at the hand-actuated or foot-actuated master brake cylinder  7 ,  13 . 
         [0052]    In the simplest embodiment, the two pump suction valves  24 ,  25  are designed as non-return valves, preferably non-return ball valves, which are closed by spring force in the home position and which can be opened hydraulically. Electromagnetic suction valve control would theoretically also be conceivable. 
         [0053]    In all exemplary embodiments, the pump  9  is designed as a piston pump whose pump pistons are combined with the two pump suction valves  24 ,  25  in the block-like brake unit  11  which serves to accommodate the inlet and outlet valves  6 ,  12 , the cut-off valve  19  and switching valve  20 , the pressure sensors  1 ,  2 ,  3  and the two low-pressure accumulators  16 . 
         [0054]    With regard to the two low-pressure accumulators  16 , it should be noted in all exemplary embodiments that, in each case, that low-pressure accumulator  16  which is arranged in the brake circuit which does not have the cut-off valve  19  and switching valve  20 , does not require a pressure retaining valve  28 , which promotes the secondary circuit ventilation and the structural expenditure in said region. 
         [0055]    While preferred embodiments of the invention have been described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. It is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.